Pyrrhalta viburni (Paykull), a new landscape pest in the United States, is univoltine and overwinters in the egg stage, feeding as larvae and adults on the foliage of plants in the genus Viburnum. Experiments were conducted to determine chilling requirements for completion and breaking of diapause and development rate of larvae at different temperatures in the laboratory. Egg hatch required at least 4 mo for induction of diapause, and ≈200 growing degree-days (GDD) at a calculated base temperature of 8.2°C for breaking of diapause in the laboratory. Development of all larval instars was significantly faster at 22 than at 17°C and faster at 27 than at 22°C, but 27°C appeared to be nearing the upper developmental threshold, because mortality was uniformly high, and deformities of adults were observed. We confirmed that larvae pass through three instars and found that head capsule width increased geometrically with instar. We calculated the larval developmental threshold to be ≈11.7°C at constant temperatures in the laboratory. Development under ambient conditions, where temperatures fluctuate, was considerably faster than that observed in the laboratory at constant temperatures. Thus, rearing experiments conducted in the laboratory at constant temperatures provide useful estimates of threshold temperatures but unrealistic estimates of GDD thresholds for P. viburni and other insects whose developmental rate differs between constant and fluctuating temperatures.

Detailed life tables and reproduction were studied in nymphs and adult females of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) fed larvae of Galleria mellonella L. (Lepidoptera: Pyralidae) at constant temperatures of 18, 22, 26, and 30°C. Development rates were fitted to the equation Y = a b ln x. The theoretical development threshold was calculated as T₀ = exp (−a/b), resulting in T₀ = 12.48 and 12.78°C for females and males, respectively. Degree-days for development ranged from 233.92 in males at 18°C to 338.73 in females at 30°C. In all temperature treatments, P. maculiventris immatures consumed a mean of approximately eight prey items. Mean immature body weights were higher at higher temperatures, but females were heavier than males only at the fifth instar. In adult female P. maculiventris, age at first oviposition ranged from 2.7 d at 30°C to 13.4 d at 18°C. Percentage of egg hatch was lowest at 18°C (11%) and highest at 30°C (36.4%). Survivorship curves showed a linear decline with time, the steepest curves at the highest temperatures. Total number of eggs laid per female ranged from 429.4 at 18°C to 755.4 at 26°C. Mean egg numbers were fitted to a surface equation as eggs = (−6.658 0.432T) d exp(−0.002Td) where d and T are age (days) and temperature (°C), respectively. Net and gross reproductive rates were highest at 26°C (R₀ = 379.126; gross reproductive rate [GRR] = 491.273 ♀/♀) and lowest at 18°C (R₀ = 207.873; GRR = 294.972). Generation and doubling times were shortest at 30°C (T = 35.021 and DT = 4.270 d). Intrinsic and finite rates of increase were also highest at 30°C (r = 0.1623; λ = 1.1763). Reproductive parameters were recalculated using numbers of eggs that actually hatched, resulting in lower values, although the effects of temperature did not change. In the context of mass rearing P. maculiventris, 26°C is the optimal temperature tested, but female predators >21 d should be not be used because they may not be capable of laying viable eggs.

Pepper weevil, Anthonomus eugenii Cano, is the major arthropod pest of peppers, Capsicum spp. L., in tropical and subtropical America. Adult weevils feed and oviposit in buds, flowers, and, especially, fruit. Larvae develop and feed inside those plant structures, thus reducing crop yields. Management is difficult and requires precise knowledge of developmental times and thresholds for maximum efficiency. Therefore, the developmental biology and life history parameters of A. eugenii were characterized in the laboratory on Capsicum annuum ’Jalapeño’ fruits at seven constant temperatures ranging from 15 to 33°C. A. eugenii developed through three instars at all temperatures. Linear regression analysis estimated a lower developmental threshold of 9.6°C and a degree-day requirement of 256.4 for development from egg to adult. Fecundity increased with increasing temperatures to a maximum at 30°C but declined at 33°C. Net reproductive rate (R_o), intrinsic rate of increase (r_m), and finite rate of increase (λ) were greatest at 30°C, whereas development time and mortality were least at this temperature regimen. Thus, 30°C proved to be the optimal temperature for population increase because a maximum fecundity of 3.1 eggs/female/d, the shortest development time of 12.9 d, minimal mortality, and the highest life history parameters were obtained. This information should prove useful for predicting infestations, timing insecticide applications, and using other control strategies.

Food sources, mineral redistribution, and excreta are some of the ways ants enrich their mound environment. Phosphorus excretion has not been reported in red imported fire ants, Solenopsis invicta Buren. Quantification of phosphoric acid in worker fecal droplets and larval anal liquid of S. invicta was performed. Phosphoric acid was trimethylsilylated using N,O-bis(trimethylsilyl)trifluoroacetamide, and the tris(trimethylsilyl) phosphate was analyzed using gas chromatography-mass spectrometry. Phosphoric acid made up 2.13 ± 1.08% (SD) of the dry weight of worker fecal droplets and 2.09 ± 0.72% of the larval anal liquid. The rate of phosphoric acid production in workers was 0.08 ± 0.024 μg/ant/d. Because the hindgut of red imported fire ant larva is separated from the midgut, the excretory products in larval anal liquid are primarily of metabolic origin. The presence of phosphoric acid in larval anal liquid shows that red imported fire ants excrete phosphoric acid.

Field trapping studies were conducted to determine whether feral blueberry maggot flies, Rhagoletis mendax Curran, and Eastern cherry fruit flies, R. cingulata (Loew), respond to natal host-fruit volatiles. Subsequent experiments were conducted to evaluate the potential of using simple and inexpensive fruit juice concentrate lures to monitor these key pests of blueberries and cherries, respectively. The presence of ripe blueberries and ripe tart cherries in enclosures that permitted escape of fruit volatiles significantly increased captures of R. mendax and R. cingulata, respectively, on adjacent sticky traps compared with traps without adjacent fruit. R. mendax were not affected by addition of blueberry concentrate to Pherocon AM traps with or without ammonium acetate. Pherocon AM boards prebaited with ammonium acetate directly incorporated into the sticky Tangle-Foot coating were equally effective as unbaited Pherocon AM boards deployed with separate ammonium acetate dispensers for monitoring R. mendax. A cherry juice concentrate increased captures of R. cingulata on unbaited Pherocon AM but not Rebell traps. In addition, combining cherry juice concentrate and ammonium acetate on Pherocon AM traps increased captures of R. cingulata compared with captures on traps with either stimulus alone. Adding ammonium acetate lures to Rebell traps more than doubled captures of R. cingulata over that on unbaited Rebell traps. Our results show that feral R. mendax and R. cingulata flies are attracted to the volatiles emitted from their host fruit and that this may be exploited to improve monitoring of these important fruit pests.

We conducted seven behavioral choice tests with Lindgren multiple-funnel traps in stands of mature lodgepole pine in British Columbia, from 1988 to 1994, to determine the dose-dependent responses of the mountain pine beetle, Dendroctonus ponderosae Hopkins, to its pheromones. A multifunctional dose-dependent response was exhibited by D. ponderosae to the pheromones cis- and trans-verbenol in areas with low population numbers. In an area with a high population level of D. ponderosae, the response was directly proportional to release rates. No dose-dependent response was exhibited by D. ponderosae to exo-brevicomin at low release rates. At rates of release >0.5 mg/d, exo-brevicomin interrupted the attraction of D. ponderosae in a dose-dependent fashion. The bark beetle predators, Enoclerus sphegeus (F.) and Thanasimus undatulus (Say), showed dose-dependent responses to only a few pheromones, with trap catches directly proportional to release rates. The multi-functional response of D. ponderosae to verbenols is consistent with an optimal attack density hypothesis.

Traps baited with ethyl (E, Z)-2, 4-decadienoate (pear ester) or (E, E)-8,10-dodecadienol (codlemone) were used to monitor codling moth, Cydia pomonella L., (Lepidoptera: Tortricidae) in 102 apple, Malus domestica Borkhausen, orchards. All orchards were treated with 500–1,000 Isomate-C PLUS dispensers/ha during 2000–2002. Traps baited with pear ester caught their first moth significantly later on average than the paired codlemone-baited traps, but timing of peak moth catch during each moth flight coincided with both types of lures. The timing of first male moth capture in pear ester–baited traps was significantly earlier than the first female moth; and the percentage of male moths in the total numbers of moths captured ranged from 55 to 60% over the three seasons. The percentage of female moths caught by pear ester–baited traps that were mated exceeded 80% each year. Pear ester–baited traps caught similar numbers of moths as codlemone-baited traps during 2000. However, the density of sex pheromone dispensers per hectare was increased in most orchards in 2001–2002; and pear ester outperformed codlemone-baited traps in both years.

This study evaluated the diversity and abundance of existing natural enemies of soybean aphid, Aphis glycines L., under field conditions in New York State, with emphasis on entomopathogenic fungi. In 2003, five soybean fields were occasionally sampled to estimate abundance and species composition of entomopathogenic fungi. During 2004, five soybean fields and adjacent buckthorn were sampled weekly. Seven species of aphid pathogenic fungi were found, including Pandora neoaphidis (Remaud. et Henn.) Humber, Conidiobolus thromboides Drechsler, Entomophthora chromaphidis Burger et Swain, Pandora sp., Zoophthora occidentalis (Thaxter) Batko, Neozygites fresenii (Now.) Remaud. et Keller, and Lecanicillium lecanii, (Zimm.) Gams et Zare. P. neoaphidis was the most abundant species, causing 84% infection in an outbreak aphid population in 2003, after which the aphid population crashed. In 2004, we found the first aphids with fungal infections in late June to midJuly. Mycosis was strongly associated with aphid density, especially during increasing aphid populations. In agreement, epizootic levels of infection were associated with subsequent declines in aphid populations. There was variability among fields; in three of five fields sampled in 2004, the chances for infection were more than five times higher than in the other two fields. High infection levels were found on aphids on buckthorn over 3 wk in autumn. Three species of aphidiid parasitoids from A. glycines were documented: Aphidius sp. and two Praon species. Both genera were the first records from A. glycines in the United States. Coccinellids were the most abundant predator, followed by syrphids and cecidomyiids, whereas anthocorids and chrysopids were less common.

Nymphs of Perillus bioculatus F., a specialist pentatomid predator of the Colorado potato beetle, Leptinotarsa decemlineata (Say), are smaller than comparable instars of their prey. In laboratory experiments, P. bioculatus fed small prey exhibited greater capture success, increased survivorship, and faster development to adulthood than individuals fed large prey. An increase of potato beetle prey stage by one instar lowered capture success and survival by 82 and 80%, respectively. Although multiple P. bioculatus are commonly found feeding on a single prey in the field, laboratory survival rates, and development times did not differ significantly between Perillus bioculatus reared individually and in groups. P. bioculatus presented with two prey sizes most commonly attacked the instar that was easiest to capture and that maximized survival. In the absence of augmentative release programs, P. bioculatus is unable to regulate L. decemlineata populations. At the study site in Yakima, Washington, L. decemlineata completes one to three generations per year in potato fields, never reaching stable age distribution before the end of the growing season. Consequently, small, easily captured prey are present only episodically. Developing P. bioculatus must therefore feed on large prey during much of the growing season, limiting their capacity to grow and survive, which is hypothesized as one reason for their failure to regulate L. decemlineata populations. Typically, invulnerable prey stages stabilize predator–prey dynamics. The evidence presented here suggests that prey refuges can also destabilize predator–prey interactions by limiting the capacity of predators to numerically respond and to regulate prey populations.

Pheromone traps were used to assess the distribution of two pheromone races of European corn borer, Ostrinia nubilalis (Hübner), in North Carolina, ≈10 and 20 yr after previous, similar assessments. In the previous studies, moths responding to a 97Z: 3E isomeric blend (Z blend) of 11-tetradecenyl acetate predominated in the far western parts of the state, whereas moths responding to a 3Z: 97E blend (E blend) prevailed in the east, with a substantial zone of overlap occurring in the eastern Piedmont. There was evidence that the E responsive population had expanded westward between 1978 and 1988. In this study, the distribution of the two races seemed to remain essentially unchanged from that observed in the late 1980s, and no evidence of a continued westward expansion of E responsive moths was detected.

The leatherback turtle (Dermochelys coriacea) (Vandelli, 1761) is classified by the IUCN (The World Conservation Union) as a critically endangered species. Hatching success is as low as 35% in French Guiana, which hosts ≈40% of the worldwide nesting activity. It has recently been shown that mole crickets contribute to the destruction of the leatherbacks at the Amana Natural Reserve. The aim of this paper is to document our observations about these potential predators of marine turtles. Identification keys and sound recordings are provided for Scapteriscus didactylus (Latreille, 1804) and Scapteriscus borellii (Giglio-Tos, 1894), mole cricket species that live in French Guiana. An abundance index of the presence of juveniles and adults was developed to study mole cricket populations in turtle rookeries and promote new observations.

We evaluated the effect of four different forest management techniques, unthinned control and three thinning intensities (light, light with gaps, and heavy thin), on arthropod abundance, diversity, and community structure as an indicator of ecological processes affecting other forest fauna. Ground-dwelling arthropods were collected during 2000–2001, with pitfall traps in June (warm-wet season) and August (hot-dry season) 5 yr after a thinning treatment in 40- to 60-yr-old Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] trees in the Willamette National Forest. We found arthropod abundance and diversity was higher in heavy and light/gap thinning treatments than the other treatments. Additionally, four groups (ants, spiders, camel-crickets, and millipedes) preferred the more intense thinning treatment areas. The abundance of carabids, the third most abundant group, was higher at the unthinned control than any thinning treatment during the wet season, but not during the dry season. Although the immediate disturbance associated with thinning might be expected to decrease population density of fauna such as ground beetles, we hypothesized that the principal effect of thinning was to increase habitat heterogeneity in these uniform plantations and indirectly increase species richness and abundance of soil-dwellers. Nonmetric multidimensional scaling (NMS) of overall arthropod community composition revealed that both seasonality and thinning were highly significant, resulting in four separate clusters of points, with season dominating thinning. Both variables were correlated with litter moisture. The NMS results indicated that ants preferred heavy thinning intensity. Spiders, carabids, and millipedes were positively associated with litter moisture, and camel-crickets were negatively associated with litter moisture. Overall, our results suggest that some dominant groups of ground-dwelling arthropods are sensitive indicators of environmental change, such as forest thinning.

During June 2003, an exploratory dung beetle survey (Coleoptera: Scarabaeidae: Scarabaeinae) was conducted in southwest Ghana at the southern edge of Ankasa Conservation Area, which is a 500-km² conserved region of the threatened Eastern Upper Guinean rainforest. The survey provided a quantitative assessment of peripheral deforestation effects and an inventory for species on omnivore dung. Pitfall traps baited with pig dung were placed in both selectively logged and unlogged rainforest as well as in nearby oil palm and cacao plantations. The Ankasa forest inventory was mostly comprised of species previously trapped by human dung in the Western Upper Guinean rainforest of Taï National Park, Côte d’Ivoire. However, there was relatively low species abundance similarity between the June/July assemblages on omnivore dung in Taï and Ankasa rainforests, and even lower similarity between assemblages of Ankasa and the adjacent plantations. Of 29 species recorded in Ankasa forest, most were absent or rare in plantations where assemblages were numerically dominated by species previously recorded from the West African savannas. This replacement plantation fauna showed significantly lower species richness and diversity, but significantly higher abundance, compared with Ankasa forest assemblages. The results reiterate that forest reserves are essential for the conservation of specialist rainforest dung beetle species.

Predator effects on prey traits change competitive interactions between prey species affecting resource use. Parasitic phorid flies limit competitive-dominant ant activity, potentially meditating competitive interactions between ant species, changing competitive hierarchies, or affecting ant communities. I considered interactions between phorids (Pseudacteon sp.), their ant host (Azteca instabilis F. Smith), and co-occurring ant species in coffee agro-ecosystems testing whether phorids (1) limit A. instabilis recruitment activity, (2) affect competitive interaction between ant species, and (3) are associated with other species’ resource access and therefore have the potential to change competitive hierarchies. I monitored recruitment of A. instabilis and other ants to baits over 90 min on canopy trees with or without phorids. A. instabilis were one-half as abundant with phorids. Other species gained access to baits 12 times more often and were only able to take over baits when phorids were present. Furthermore, many more species (13 versus 2) gained access to resources when phorids were present. These results indicate that phorids mediate competitive interactions between ant species and may influence ant communities by affecting resource availability. Considering that phorids limit A. instabilis attacks on herbivores and that ant species differ in effects on arthropod communities, phorids may have strong community-level effects in coffee agro-ecosystems.

Patterns of arthropod richness and diversity were studied across six hybrid zones within the silversword alliance (Asteraceae: Heliantheae-Madiinae), an adaptive radiation of endemic Hawaiian plants. Hybrid zones spanned a range of parental plant relatedness from those in which parental types were phenotypically and genetically similar to those in which parental types were different both phenotypically and genetically. This system of hybrid zones is uniquely suited for distinguishing among alternative hypotheses that account for biodiversity of herbivores in plant hybrid zones. In the six hybrid zones studied, arthropod family-level diversity was as high or higher on hybrid plants compared with parental plants. Family-level richness was as high or higher on hybrids plants in four cases and lower on hybrids in two cases. Generally, results were consistent with hypotheses that predict either a breakdown in insect defenses in hybrid plants or an additive increase in host recognition cues in hybrids. Hypotheses that predict an increase in hybrid resistance to herbivory were supported in two cases. Measures of community similarity suggest insect communities are more similar to each other on hybrid–parent pairs than are communities on parent–parent pairs and that insect communities across interspecific hybrid zones are more similar than communities across intergeneric hybrid zones. In four zones, hybrids supported unique arthropod taxa. Because a greater or equal diversity of arthropods is found on hybrids than on parental plant taxa and because hybrid plants may represent unique environments to insects, plant hybrid zones are important targets for conserving Hawaii’s native biota.

Grassland fires have been shown to influence grasshopper community composition and population dynamics, but studies of their effects on rangeland grasshopper assemblages in the northern Great Plains are lacking. This study was designed to examine the effect of a grassland wildfire on grasshopper community composition and population densities of three grasshopper subfamilies in western North Dakota northern mixed-grass prairie with sampling in paired burned and unburned plots. A rapidly moving fire occurred in late October 1999, after egg-overwintering grasshoppers had died. Vegetation biomass and nitrogen content of grasses did not differ statistically between burned and unburned plots in 2000. The fire negatively affected grasshopper population densities the year after the fire, but species diversity was not affected by the fire. Much of the reduction in grasshopper population densities was caused by a decline in densities of Gomphocerinae species. Grasshopper subfamily densities did not differ statistically between burned and unburned plots in 2001. Additional research is needed to determine the mechanisms leading to the reduction in Gomphocerinae species densities.

The ecological interactions between grasshoppers, predators, and resources that can limit the population growth of grasshoppers are poorly understood. A number of field experiments have shown that top-down control by avian predators can limit grasshopper populations, but the effects of avian predators on grasshopper populations can differ between years and between sites in the same habitat. I conducted experiments examining grasshopper populations in avian exclosures and control plots for 3 yr at two locations in eastern Montana. Avian predation had variable direct and indirect effects on grasshopper communities at the two locations. Grasshopper population densities, species richness, and diversity at the two sites were not consistently significantly affected by avian predation, indicative of weaker top-down effects. The effects of predation varied among years and between the two sites. Avian predators modified body size composition of grasshopper populations through size-selective predation on medium-bodied grasshoppers. Even in years when avian predators did not limit grasshopper populations, selective predation seemed to indirectly mediate competitive interactions among grasshoppers. Birds reduced the proportion of presumably competitively superior medium-bodied grasshoppers, and small-bodied grasshoppers increased in abundance.

A 10-yr study was conducted in the Los Mochis sugarcane area in western Mexico to determine rates of parasitism by Conura acuta (F.), an indigenous pupal parasitoid of the stalkborers Diatraea considerata Heinrich and D. grandiosella Dyar. Parasitism by C. acuta was practically zero in 1993, progressively increased soon after chemical insecticide applications were discontinued in the sugarcane area, peaked at a yearly average of 3.2% in 1997, and stabilized thereafter at 2–3%, except in 2000 and 2002, probably because of drought. Seasonal parasitism by C. acuta was density-dependent, with maximum parasitism occurring during summer, when hosts were more abundant. Maximum parasitism by C. acuta occurred during mid-September 1996 with 43.3%. Although parasitism by C. acuta was generally low throughout the study, its impact may be important in terms of indispensable mortality, late in the life history of stalkborers. No field parasitism by C. acuta was observed on Eoreuma loftini (Dyar), a concurrent sugarcane stalkborer in this area. In the laboratory, the most preferred hosts by C. acuta were D. grandiosella and D. considerata with 60% parasitism, whereas E. loftini, D. saccharalis (F.), and Spodoptera frugiperda (J. E. Smith) were poorly accepted (<5%). Parasitism was highest in the youngest pupae (1 d old) and decreased progressively with host age. Late-instar larvae and prepupae were not accepted, showing that C. acuta is a true pupal parasitoid (idiobiont). Attraction and parasitism by C. acuta were higher when pupae were exposed with larval frass compared with clean pupae, suggesting the presence of a kairomone in the process of host finding and acceptance. Developmental time of C. acuta was 10 d longer on D. considerata than on D. grandiosella, with no difference between parasitoid sexes within hosts. In contrast, C. acuta longevity did not differ after emerging from either host species, with females living >20 d longer than males. Opportunities for using C. acuta, the only known pupal parasitoid of sugarcane stalkborers in Mexico, as a biological control agent are discussed.

The parasitoid assemblage associated with the citrus leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) was studied in citrus orchards in eastern Spain over a 7-yr period (1995–2001) after the leafminer’s introduction in 1994. In total, 11,587 adult native parasitoids were collected. To evaluate parasitism, 93,846 live immature stages of the citrus leafminer were observed, of which 21,460 (22.9%) were found to be parasitized. The parasitoid complex recruited around P. citrella was typical for invader hosts: lower species richness, generalized habits, idiobiont strategy, and low to moderate rates of parasitism. Two of the 10 species reared from the citrus leafminer, Pnigalio sp. and Cirrospilus brevis Zhu, LaSalle and Huang, accounted for >90% of the parasitoids. Native parasitoids moved onto the invading host rapidly, except for C. brevis, which required 3 yr to become common and widespread. In other leafminer species from plants in the vicinity of citrus orchards, the proportion of P. citrella parasitoids was higher in woody (69.7%) than in herbaceous plants (22.2%). The high population levels reached by the new pest, associated with a negative density dependence response of the parasitoids at these high population levels, suggest that the native parasitoid assemblage exerted only a limited role in regulating the population of the new host.

The microsporidium Thelohania solenopsae Knell, Allen, and Hazard was released into colonies of red imported fire ants, Solenopsis invicta Buren, at four field sites in Louisiana. Social form of the ant affected the establishment of the microsporidium; long-term epizootics developed at two sites with predominantly polygyne populations, whereas the pathogen produced a low disease prevalence before it disappeared or did not infect ants at all at two monogyne sites. This study is the first report of artificial infection of monogyne S. invicta field colonies. When the microsporidium became established in mixed monogyne/polygyne ant populations, prevalence rates peaked at >75% in both social forms. In mixed ant populations, the social form suffering higher prevalence of the disease decreased proportionally to the other form, possibly indicating a competitive disadvantage. Host population density or site characteristics may have influenced spread of the disease; the rate of spread was 0.9 m/mo at one epizootic site and reached 9.4 m/mo at the other. There was little seasonal variation in prevalence, which averaged 47% in February, 51% in April/May, and 57% in October/November at the two epizootic sites. The strongest evidence of microsporidian impact on S. invicta populations was a negative correlation between colony numbers versus percentage infection and a sporadic decrease in the number of foragers. There was some evidence of a decrease in the size and number of colonies at one epizootic site and a decrease in brood at the other. This sporadic weakening of the S. invicta populations did not lead to significant immigration of other ant species.

The effect of black stripes on the flight path of nondiapausing adult Colorado potato beetles, Leptinotarsa decemlineata (Say), was studied in a white flight chamber. Flights generally ended in even frequencies throughout the length of the chamber except for peaks of abundance immediately ahead of the release cone and immediately ahead of the white end wall. The peak of flight frequency immediately ahead of the white end wall disappeared when the end wall was covered in black. Colorado potato beetles flew toward alternating white and black vertical stripes each 3.8 cm in width but changed paths to avoid a wall of alternating white and black stripes each 11.6 cm in width. These results indicate that Colorado potato beetles in free flight, like walking beetles, have the visual ability to detect and discriminate stripes of at least 2° (11.6 cm) in width. Single vertical black stripes 5–60 cm in width were not avoided. Colorado potato beetles in flight given access to an adjacent unlit area of light intensity 53% lower than that of the lit test chamber did not enter it. The unlit area was avoided by Colorado potato beetles in flight as much as a black wall. These results indicate that the flight behavior of the Colorado potato beetle as it approaches artificial or landscape structures is affected not only by their size (visual width) but could be affected also by the change in light intensity in their neighborhood. The avoidance behavior of large black stripes and objects by nondiapausing Colorado potato beetles was also seen in beetles preparing for diapause. Contrary to walking Colorado potato beetles, flying beetles, regardless of their prediapausing status, avoided rather than moved toward wide stripes. The results are discussed within the context of Colorado potato beetle fall dispersal. The previously proposed hypothesis that the occurrence of long migratory flights oriented toward silhouetted forest edges to overwinter is in response to the exposure to diapause-inducing conditions is not supported by the experimental data.

Studies were conducted in apple to evaluate factors that differentially affect the catch of male and female codling moth, Cydia pomonella L., in traps baited with ethyl (E, Z)-2,4-decadienoate (pear ester). We examined the time of moth capture in the diel cycle and the recapture rates of marked moths in sex pheromone mating disruption (MD) and untreated orchards. The attractiveness of pear ester–baited traps was compared among five apple cultivars. Experiments also assessed the influence of trap height, the distance of the trap from sex pheromone dispensers, proximity of foliage surrounding the trap, trap size, and proximity of adjacent clean and codling moth–injured fruit on moth captures. The responses of male and female moths significantly differed in response to many of these factors. For example, the time of peak female capture occurred earlier than for males. A higher proportion of recaptured, marked moths were females in MD versus untreated orchard plots. Significantly more male but not female moths were caught in traps placed high versus low in the tree canopy. Traps placed on the perimeter of the canopy caught significantly more female moths than traps placed within the canopy and surrounded by foliage. Smaller trap surfaces caught significantly more males than females. Traps placed adjacent to uninjured fruit caught significantly more females than traps placed away from fruit. No differences occurred between sexes in response to other factors: significantly higher counts of both sexes occurred in blocks of ‘Granny Smith’ versus four other apple cultivars; recapture rates of marked moths were not different at release points ranging from 10 to 50 m for either sex; and trap placement relative to MD dispensers or injured versus uninjured fruits was not a significant factor affecting moth catches or their sex ratio. Effective monitoring for either or both sexes of codling moth should consider standardizing these factors. Lure and kill strategies should include factors that optimize the captures of female moths.

Adult feeding and oviposition preferences and larval performance of the pea leafminer, Liriomyza huidobrensis (Blanchard), were examined on pea, potato, lettuce, gai lan, celery, cucumber, and onion in the laboratory and field. Host preference for feeding and oviposition varied among pea leafminer subpopulations when density measures were used but not with proportional measures. Proportion of oviposition punctures may be a more appropriate measure of oviposition preference than egg density for leafmining flies, because it is not impacted by factors affecting stippling density. No correlations were found between preference and performance parameters in this highly polyphagous fly.

Evaluations of field research on the nontarget effects of pest management, particularly the production of transgenic crops with insecticidal properties, suggest the methods used are sometimes unlikely to detect real differences among treatments. Among potential problems, abundance estimates may be scale-dependent for many arthropods, which move among experimental plots and between experimental plots and the surrounding environment. Insecticide-disturbed plots of field corn in a range of sizes in 2003 (0.03–0.53 ha; 18–72 m wide) and 2004 (0.01–0.13 ha; 9–36 m wide) were used for testing effects of scale on nontarget arthropod abundance. Possible effects of artificially isolating plots by removal of vegetation around plot borders were also studied in 2003. Community and taxon-based analyses showed abundance of foliar (aboveground) arthropods depended on plot size and isolation. While abundance of foliar arthropods was generally greater in smaller plots, isolation treatments suggested some taxa may have been either repelled or attracted to isolated plots. Levels of some epigeal (ground-dwelling) taxa were also size or isolation-dependent, but community-based analysis did not indicate a strong collective response to treatments. Recommendation of a practical but rigorous minimum plot size for nontarget studies may not be appropriate because responses to plot size varied among taxa. However, because arthropod movement into and out of plots can reduce differences between treatments, results suggest the use of small plots (width <9 m) for nontarget studies on transgenic crops generally should be avoided. Similarly, the taxon-specific effects of isolating plots should be considered when planning studies or interpreting results.

A 6-yr field study assessed the long-term impact of Bt cotton producing the Cry1Ac δ-endotoxin on 22 taxa of foliar-dwelling arthropod natural enemies in Arizona. No chronic, long-term effects of Bt cotton were observed over multiple generations of nontarget taxa. Zero-2 taxa declined significantly in unsprayed Bt compared with non-Bt cotton each year. In contrast, positive control studies showed that insecticide applications for caterpillars and other pests in both non-Bt and Bt cotton had much greater negative effects on 10 taxa. Multivariate principal response curves supported the findings of univariate analyses for the entire natural enemy community, showing no effect of Bt cotton but large and long-lasting negative effects from the use of insecticides. Multi-year analyses provided greater statistical power and indicated significant reductions that averaged 19% in five arthropod predator taxa in unsprayed Bt compared with non-Bt cotton. Most of these reductions were likely associated with reductions in lepidopteran prey. However, results of a companion study examining natural enemy function suggest that these minor reductions in Bt cotton have little ecological meaning. Multi-year analyses showed an average significant reduction of 48% in 13 taxa for plots receiving insecticide applications. On average, a 3-yr study with four replicates per year was sufficient to discern changes of ≈20%, with 80% power in unsprayed cotton. This long-term study indicates that the effects of Bt cotton on a representative nontarget community are minor, especially in comparison with the alternative use of broad-spectrum insecticides. Guidelines for improving nontarget field studies are discussed.

Field studies to assess effects of transgenic crops on nontarget organisms primarily have focused on nontarget abundance and diversity, whereas few have examined effects on nontarget community function. A 5-yr field study in Arizona assessed whether transgenic cotton producing the Cry1Ac toxin of Bacillus thuringiensis (Bt) had an effect on the natural enemy community’s impact on three key pests. Predator:prey ratios for Bemisia tabaci (Gennadius) and Lygus hesperus Knight were similar in unsprayed Bt and non-Bt cotton. Insecticide applications in positive control plots inconsistently altered ratios for B. tabaci. Predation indices based on the known feeding activity of selected predators showed that potential predator impact was unaltered by Bt cotton but was consistently depressed with insecticide applications. Sentinel eggs and pupae of Pectinophora gossypiella (Saunders) experienced the same rates of predation in both unsprayed Bt and non-Bt cotton. Cohort-based life tables for B. tabaci showed that rates of sucking predation, parasitism, and dislodgement (chewing predation in part) were unchanged by Bt cotton. Underlying experimental designs were sufficient to consistently detect changes of <20% in predator:prey ratios and predation indices and changes of <10% in rates of P. gossypiella and B. tabaci mortality with >80% power (α = 0.05). These long-term studies showed essentially no effects of Bt cotton on natural enemy function in Arizona cotton and further showed that minor reductions in density of several predator taxa in Bt cotton observed in a companion study may have little ecological meaning relative to natural enemy impact on key pests in the system.

Transgenic Bacillus thuringiensis (Bt) cotton has had a major impact on the Australian cotton industry by largely controlling lepidopteran pests. However, it also may have other impacts on the invertebrate community that need to be identified. We compared the canopy invertebrate community in sprayed conventional, unsprayed conventional, and unsprayed Bt cotton over three seasons using suction sampling methods. We found that the diversity or species richness of the beneficial communities was reduced in the sprayed crops at two sites. Although spraying had the strongest effect on the community, there was a slight difference between the total community in unsprayed conventional and Bt crops, with crop type accounting for 4.5% of the variance between these communities. Out of over 100 species groups examined, the most consistent differences between unsprayed Bt and conventional communities were higher numbers of Helicoverpa in conventional crops (as would be expected) and slightly higher numbers of Chloropidae and Drosopillidae (Diptera), damsel bugs (Hemiptera, Nabidae), and jassids (Hemiptera, Cicadellidae) in conventional crops. With the advent of Bollgard II and the possibility that 80% of the cotton crop in Australia could be transgenic, the effects of these small differences in the transgenic and conventional communities should be monitored over the long-term to assess if any modifications to cotton management practices need to be made.

Abundance of canopy- and ground-dwelling predators was monitored in three pairs of commercial Bt and non-Bt cotton fields (5–15 ha) during three successive seasons using three sampling methods: bagged whole plants, drop cloth samples, and pitfall traps. Samples were taken throughout each growing season. Insecticides were applied to manage pests when economic thresholds were exceeded in both cotton types. Of 1,518 possible date-by-date orthogonal contrasts used to evaluate abundance of predators in all sampling methods, analysis of variance generated 23 contrasts with greater abundance in non-Bt and 20 with greater abundance in Bt cotton, comprising nine taxa. When data from all three seasons were pooled for each sampling method, only six contrasts comprising five taxa were significant, with two favoring Bt (Nabis spp. in whole plant inspections and spiders in drop cloths) and four favoring non-Bt cotton [Hippodamia convergens Guérin-Méneville in drop cloths and whole plant inspections and lady beetle eggs and Geocoris uliginosus (Say) in whole plant inspections]. The shift in abundance of canopy-dwelling taxa—especially coccinellids—between Bt and non-Bt cotton fields was likely associated with insecticide use. Analyses of predator community dynamics using principal response curves showed that the abundance of ground-dwelling predators was not affected by cotton type, whereas abundance of canopy predators varied across seasons with no particular trend for either cotton type. The abundance of predators across 3 yr in cotton fields with standard grower practices failed to exhibit any negative impact of Bt cotton on predator populations.

Field studies were conducted in 2000–2002 to compare foliage-dwelling arthropod populations on Bacillus thuringiensis Berliner (Bt) (Bollgard) cotton and non-Bt (conventional) cotton season-long in South Carolina, Georgia, northern Alabama, and southern Alabama. For each of these four regions, three or four paired fields were sampled weekly in each of the 3 yr. Each pair of fields consisted of a Bt and a non-Bt cotton field, both at least 5 ha in size. The dominant arthropod taxa collected included target pests (heliothine moths and Spodoptera spp.), nontarget pests (stink bugs and plant bugs), and generalist natural enemies [Geocoris spp., Orius spp., Solenopsis invicta (Buren), ladybeetles, and spiders]. Where target pests were present, particularly Helicoverpa zea (Boddie), their numbers were consistently significantly lower in the Bt cotton fields. Natural enemy populations generally were not significantly different between the Bt and the non-Bt cotton fields (50% of all comparisons) and, where significant differences were present, natural enemy abundance usually was higher in the Bt than the non-Bt cotton fields. These differences were correlated with lower insecticide use on the Bt than the non-Bt cotton fields, particularly in South Carolina, where target pest pressure was heaviest. When presented with insect eggs or larvae as prey items, the larger natural enemy populations in Bt cotton fields exhibited significantly higher predation rates. These results show that Bt cotton has no significant adverse impacts on the nontarget arthropod populations studied and, compared with insecticide-treated non-Bt cotton, Bt cotton supports higher natural enemy populations with significant positive impacts on biological control.

A field experiment was conducted over 3 yr to assess the effects of transgenic field corn expressing stacked lepidopteran-active Bacillus thuringiensis (Bt)-derived VIP3A and Cry1Ab proteins on nontarget arthropods. Effects were compared with an isogenic conventional corn hybrid treated with a foliar insecticide and an isogenic control without insecticides. Plant inspections, pitfall traps, sticky cards, and emergence traps determined the abundance and diversity of plant, aerial, and surface-dwelling communities. More than 500,000 arthropods were enumerated, representing 203 taxonomic groups in 112 families and 13 orders. In terms of abundance, 70% of the arthropods were saprovores, 13% were herbivorous insects, 14% were predators, and 3% were parasitoids. Overall biodiversity and community-level responses were not significantly affected by expression of the stacked VIP3A and Cry1Ab proteins. Densities of most nontarget taxa exposed to the Bt hybrid showed no differences compared with the isogenic control. However, significant changes in certain taxa did occur in the Bt plots, which were indirectly related to plant-mediated factors, prey density responses, and the absence of plant injury. Arthropod communities in the insecticide-treated plots displayed both negative and positive changes in the abundances of individual taxa. Together, effects observed in the Bt plots were significantly less than the community disturbances caused by insecticide applications. Changes in nontarget communities in plots previously exposed to insecticides and the Bt hybrid did not carryover to the following growing season. Major arthropods as bioindicators, routes of exposures, and food web interactions relative to the observed effects are discussed.

Field populations of nontarget arthropods in transgenic corn with the MON 810 event expressing the Cry1Ab endotoxin from Bacillus thuringiensis variety kurstaki (Bt) were compared with those in conventional, near isogenic corn. The study was conducted at two locations in Georgia in 2001 and 2002 using visual counts, pitfall traps, and corn ear insect evaluations. Results were analyzed by trial using a repeated-measure analysis of variance (ANOVA) and a combined ANOVA of all trials. The only insect whose numbers were strongly affected by the Bt corn was the corn earworm, Helicoverpa zea (Boddie), a target insect. When averaged over all trials, larvae and adults of sap beetles, Carpophilus spp. (mostly C. lugubris Murray), and larvae of the otitid fly Euxesta stigmatis Loew were less abundant on Bt than non-Bt corn ears. Kernel damage caused by H. zea was less in Bt corn, which presumably made Bt corn ears less attractive to these insects. There were no consistent significant differences in nontarget phytophagous and predaceous arthropods in the visual counts and pitfall traps between Bt and non-Bt corn. One exception was Nabis spp., which was less abundant in Bt than non-Bt corn in the combined analysis. Flea beetles, mostly corn flea beetle, Chaetocnema pulicaria Melsheimer, were more abundant on Bt than non-Bt corn in the combined analysis but presumably were not adversely affected by the Bt corn. With the exception of nabids, these results indicate that transgenic Bt field corn containing the MON 810 event did not have an adverse effect on populations of nontarget phytophagous or predaceous arthropods in the Georgia corn system.

Large-scale field studies were conducted to determine if temporal plantings of Bacillus thuringiensis (Berliner) (Bt) corn (event 176 and Bt11) would affect the seasonal abundance of the following generalist predators: Coleomegilla maculata DeGeer and Cycloneda munda (Say) (Coleoptera: Coccinellidae), Orius insidiosus (Say) (Heteroptera: Anthocoridae), Chrysoperla carnea Stephens (Neuroptera: Chrysopidae), and one specialist parasitoid, Macrocentrus cingulum Brischke (Hymenoptera: Braconidae). Adult populations were monitored using Pherocon AM yellow sticky traps at three locations in Iowa (1996–1998). At each location, a split-plot design was used with Bt and non-Bt corn as main plots and three planting dates as the split plots. Few differences in abundance were observed between Bt and non-Bt corn for the generalist predators studied. However, M. cingulum, a specialist parasitoid of European corn borer, was significantly affected by the presence of Bt corn. Densities of adult M. cingulum were 29–60% lower in Bt corn compared with non-Bt corn. Regression analyses indicated M. cingulum adults were preferentially recruited to and subsequently increased over time in the non-Bt corn treatments at each location within each year. Significant differences were observed among planting dates for all five species. Abundance effects from Bt corn on these natural enemies were not unexpected given the foraging and searching behaviors of different species and their varying levels of dependence on the presence of European corn borer.

Characteristics of ground beetles (Coleoptera: Carabidae), including their distribution, diet breadth, and importance as generalist predators, make them candidates for evaluating potential unintended effects of transgenic crops. The abundance and composition of carabids collected from pitfall traps placed in hybrid dent corn were used to determine which species are consistently present and abundant in Iowa carabid communities and to test for population differences in these species caused by transgenic (Bacillus thuringiensis [Bt]) or insecticide-based pest management. Power analyses were also used to evaluate the adequacy of the experimental design. Carabid collections indicate Harpalus pensylvanicus DeGeer is the best choice to sample based on its apparent ubiquity and abundance in Iowa and other corn-producing states. However, population levels were time-dependent, and composition of carabid communities differed between locations. Considering the numerical dominance of a few species per field, the two to four most abundant species might be used to effectively represent local carabid communities. H. pensylvanicus populations were impacted by insecticide use, but no effects of Bt were found. Power analyses indicated that with the experimental design and replication employed, only large effects were detectable; based on the variation between plots, increased replication is needed to make detection of either moderate (30–50%) or small (<30%) effects likely. The recent release of transgenic corn with coleopteran toxicity highlights the importance of these results when evaluating potential unintended effects of these crops on ground beetles. One species not previously recorded in Iowa, Lebia pulchella Dejean, also was collected.

A 3-yr field study was conducted in Monmouth, IL, to evaluate the effect of transgenic Bt corn expressing a Cry3Bb1 protein (MON 863) on ground-dwelling invertebrates. The study employed a split-plot design with MON 863 corn and a conventional near isoline (RX670) as the main plots, and insecticide regimens as subplots. Ground-dwelling arthropods were sampled with pan and pitfall traps during each of the 3 yr (2000–2002). The most abundant taxa collected included generalist predators, such as Araneae (spiders), Carabidae (ground beetles), and Staphylinidae (rove beetles), and detritivores (decomposers), such as Japygidae (diplurans), Lathridiidae (scavenger beetles), Formicidae (ants), Chilopoda (centipedes), and Oligochaeta (earthworms). MON 863 had no consistent adverse impacts on the abundance of any nontarget, ground-dwelling taxon compared with the non-Bt isoline; significant line effects were seen with only 2 of 14 nontarget taxa analyzed, and the nature of these effects varied within and among years. In contrast, certain insecticide applications had consistent adverse impacts across all 3 yr on diverse groups of ground-dwelling predators such as spiders and decomposers like diplurans. Foliar (permethrin)- and soil (tefluthrin)-applied insecticides significantly decreased the abundance of ground beetles and spiders compared with an insecticidal seed treatment (imidacloprid) or no insecticide application. Overall, significant effects of insecticide regimen were seen with 6 of the 14 nontarget taxa analyzed. Adoption of MON 863 and the concurrent reduction in broad-spectrum soil-applied insecticide use for the control of larval Diabrotica spp. have the potential to enhance the role of biological control within corn agroecosystems.

A 3-yr field study was conducted in Monmouth, IL, to evaluate the effect of transgenic Bt corn expressing a Cry3Bb1 protein (MON 863) on foliage-dwelling arthropods. The study employed a split-plot design with MON 863 corn and a conventional non-Bt near isoline (RX670) as the main plots and insecticide regimens (no insecticide, imidacloprid applied as seed treatment, tefluthrin applied as soil treatment, and permethrin applied as foliar treatment) as subplots. Foliage-dwelling arthropods were sampled with sticky traps during each of the 3 yr (2000–2002). The most abundant taxa collected included corn pests, such as Diabrotica virgifera virgifera LeConte and Chaetocnema pulicaria Melsheimer (Coleoptera:Chrysomelidae), and Rhopalosiphum maidis Fitch (Homoptera:Aphididae). The most abundant generalist predators captured by sticky traps were Coccinellidae (ladybird beetles), Nabidae (damsel bugs), Orius insidiosus Say (minute pirate bugs), Syrphidae (flower flies), Chrysoperla carnea Stephens (green lacewings), Macrocentrus cingulum Rienhardt (a braconid parasitoid), and Araneae (spiders). MON 863 corn had no consistent adverse impact on the relative abundance of any nontarget foliage-dwelling arthropod taxon, including predators and parasitoids. However, insecticide applications of foliar insecticide (permethrin) significantly and consistently decreased the abundance of ladybird beetles, green lacewings, and damsel bugs compared with the insecticidal seed treatment or no insecticide application. The abundance of the pest R. maidis also was observed to increase in the foliar-applied insecticide treatment. Therefore, adoption of MON 863 and the concurrent reduction in broad-spectrum foliar-applied insecticide use for control of adult Diabrotica spp. have the potential to enhance biological control within corn agro-ecosystems.

Springtails are an integral and beneficial part of the soil community. As part of an extensive study of the effect of rootworm Bt corn (Cry3Bb1) on nontarget invertebrates, we evaluated both the abundance and diversity of surface-active (epedaphic) and subsurface (euedaphic) springtails at Ames, IA, and Monmouth, IL, in 2-yr field trials during 2000–2002. Springtails were collected from pitfall traps and soil cores in plots planted with rootworm Bt corn and its non-Bt isoline. Few differences were observed in the abundance of individual species in Bt and isoline corn. Nor did the estimated species richness or the Shannon or Simpson diversity indices differ significantly between Bt and isoline corn at either location during 2000–2002, indicating no effect of Bt corn on springtail diversity. In soil insecticide-treated plots, however, springtails were consistently more abundant than in check plots, perhaps because of adverse insecticide effects on springtail predators. Soil insecticide also reduced both Shannon and Simpson diversity in the Iowa euedaphic and Illinois epedaphic populations. Such consistent insecticide effects on both abundance and diversity of springtails provide a positive control by which to assess the power of the experimental design to detect a comparable impact of Bt corn on springtails. They also show that insecticide use more strongly impacts springtails and their predators than does the practice of growing transgenic crops to control the same pests.