The developmental rates of Oulema duftschmidi (Redtenbacher) eggs, larvae, and pupae were studied at different constant temperatures. A linear regression model was fitted to the data obtained in this and in a previous study within a temperature range where the rate proportionally increases with temperature. Ratios of SEs to the mean thermal constant and to the mean developmental threshold indicated that reliable estimates have been obtained for the three life stages. Within the framework provided by the metabolic theory of ecology, a growth-based model was evaluated to explain developmental rates in the entire temperature range permissive of development of the three life stages. The model is based on component functions describing growth patterns through time, temperature-dependent consumption rates of biomass, transformation of consumed food into body biomass change, and respiration rates with respect to temperature. Experimental data were used for the selection and validation of models and for the estimation of the parameters of different regression models. Limitations and opportunities for using the growth-based model to explain developmental rates are discussed. An empirical function was used to describe the variability of developmental rates.

The feeding and oviposition activity of overwintering boll weevils, Anthonomus grandis grandis (Boheman), and seasonal fluctuations in development, survival, and reproduction of progeny of overwintering and first- and second-generation boll weevil females were determined in the laboratory at 27°C, 65% RH, and a photoperiod of 12:12 (L:D) h. During the cotton-free period in the Lower Rio Grande Valley, female boll weevils without access to cotton resorb their unlaid eggs and enter reproductive diapause. However, when they were provided daily with greenhouse-grown cotton squares, commencement of oviposition began after 7, 15, or 20 d, depending on when they were captured. Females captured later in the winter fed longer before laying eggs than those captured in the early fall, suggesting that it may take females longer to terminate diapause the longer they have been dormant. The rate of feeding by females was significantly less during the winter months, and this may have affected the rate of diet-mediated termination of dormancy. Females of the first and second generations after the overwintering generation produced a significantly higher percentage of progeny surviving to adulthood and a higher proportion of these progeny were females. Offspring development time from overwintering female parents was significantly longer than that from first and second generations under the same laboratory conditions. The total number of lifetime eggs produced by females of the second generation during the cotton-growing season were ≈9.9-fold higher than for overwintering females and 1.5-fold higher than for first-generation females. Life table calculations indicated that the population of second-generation boll weevils increased an average of 1.5-fold higher each generation than for females of the first generation and 22.6-fold higher than for overwintering females. Our data showed variation in boll weevil survival, development, and reproductive potential among the overwintering and first- and second-generation females, suggesting inherent seasonal fluctuations in these parameters.

The performance of two aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday), against Aphis gossypii Glover on greenhouse cucumber (Cucumis sativus L.) and Myzus persicae (Sulzer) on sweet pepper (Capsicum annuum L.) were evaluated at various constant temperatures. Biological parameters of both parasitoids including developmental time, pupal survivorship, percentage of parasitism, and sex ratio of the progeny were studied at 5, 10, 15, 20, 25, 30, and 35°C. At 25°C, an average of 10.0 ± 1.1 and 9.8 ± 1.1 d was needed for A. colemani to complete its development from oviposition to adult eclosion on A. gossypii and M. persicae, respectively. The corresponding average times needed for A. matricariae were 11.9 ± 0.9 and 11.5 ± 1.1 d, respectively. The lower developmental thresholds for A. colemani reared on A. gossypii and M. persicae were estimated from linear regression equations to be 2.97 and 2.65°C, respectively, whereas these values for A. matricariae were 3.37 and 3.51°C, respectively. Parasitization rate of both parasitoid species, recorded as percent aphids mummified, increased almost linearly with increasing temperature to reach a maximum at 25°C and decreased at 30°C. The optimal temperatures for development of A. colemani and A. matricariae were ∼30 and 25°C, respectively, and high mortality occurred at higher temperatures. The Lactin 2 and Briere 1 developmental models were accepted based on their excellent goodness-of-fit to the data (residual sum of square and coefficient of determination) and estimable temperature thresholds and are strongly recommended for the description of temperature-dependent development of A. colemani and A. matricariae.

The behavioral responses of Hylamorpha elegans L. (Coleoptera: Scarabaeidae, Rutelinae) to the semiochemicals released from conspecific individual adults were studied, with particular attention paid to female attraction of males. Odors released from virgin females significantly attracted male conspecifics in both the field and laboratory olfactometer and wind tunnel bioassays. However, females did not attract other females, and males attracted no one. The response of male H. elegans to (1) compounds (1,4-hydroquinone and 1,4-benzoquinone) released only by unmated females; (2) the essential oil of the secondary host (Nothofagus obliqua); and (3) the blend of 1,4-hydroquinone and 1,4-benzoquinone with N. obliqua essential oil was studied. The blend of 1,4-benzoquinone mixed with essential oil at the trial concentration was attractive with males. The same response was found with 1,4-hydroquinone alone. The essential oil did not have the expected attractant effect on conspecific males. These results suggest that, when combined with essential oil, 1,4-benzoquinone may function in the sexual behavior of males and females. These findings are discussed in terms of the ecological role of this putative sexual pheromone and its potential use in a strategy of control of this pest.

The old-house borer, Hylotrupes bajulus (Linnaeus) (Coleoptera: Cerambycidae), has been a very serious pest of structural timber in many parts of the world. The available semiochemical-based trapping method typically results in low capture rates. In this study, efforts were made to improve the semiochemical-based trapping method using screen cage assays conducted in the greenhouse. Ground traps baited with two vials of (3R)-ketol 1-butanol (pheromone baited) caught >21.0% adults than the alternative trap and were seen to be superior to ramp traps baited with identical compounds. Based on adult catches with pheromone-baited traps with different colors, attraction of H. bajulus adults to black was significantly greater than other colors, followed by brown, gray and yellow, red, white, green, and blue. No differences were found in adult catches to pheromone-baited traps with respect to different trap sizes. There were no statistical differences between the different semiochemicals tested. Therefore, black ground traps baited with two vials of (3R)-ketol 1-butanol plus two vials of ethyl acetate can be effective in the monitoring and potential control of H. bajulus.

As part of a program to minimize the accidental transportation of Japanese beetles (Popillia japonica) through cargo aircraft to areas where they are not established, a 4-yr trapping project was initiated to study the relative distribution and dynamics of the beetles along a trap line around the Indianapolis International Airport. Land use influence on beetle abundance (trap catch) was assessed using a geographic information system. Trap catch was consistently high in some locations and low in others. In general, high trap catches occurred near agronomic land planted with corn or soybeans, which are both preferred hosts of adult beetles. Low trap catches generally occurred in areas lacking preferred host plants. The amount of agronomic land within 500 m of the traps was always positively correlated with trap catch. Average trap catches were highly correlated by location from year to year, indicating stability of the relative distribution of the beetles along the trap line. Because high trap catches consistently occurred in the same locations, it can be inferred that trapping can be an effective method to monitor Japanese beetle populations. Taking airport-owned agronomic land out of corn and soybean production near the cargo terminals may reduce beetle activity in these areas.

Because of fire suppression and improper land management, native eastern redcedar, Juniperus virginiana L., is invading many grassland areas. Among these areas are the Loess Canyons of southeastern Lincoln County, NE, which support a large population of the federally endangered American burying beetle, Nicrophorus americanus Olivier. In the past 30 yr, cedar encroachment has covered >30% of this landscape and is increasing at a rate of 2% per year. The effects of cedar trees on remaining populations of American burying beetle are currently unknown. In this study, we sampled two sites in Lincoln County, NE, by placing paired baited pitfall traps (N = 16) in cedar-dominated and open grassland habitats during June and August 2004 and 2005. We collected significantly more Silphidae, including American burying beetle in open habitats. All American burying beetle were marked and released. The recapture rate of these beetles was two times higher in cedar sites than in open sites. Among the Silphidae, only Nicrophorus orbicollis Say was collected significantly more often in cedar areas. The results of this study indicate that cedars reduce numbers of most silphid species, likely by limiting their ability to forage for carrion, a required resource for feeding and reproduction. This is the first study to directly examine the impact of cedar on Silphidae, and our results have important implications in the Great Plains and beyond. However, future studies must examine the impacts of cedar management, including mechanical control or prescribed fire, on American burying beetle and other silphid species.

Variable retention harvesting (VRH), in which trees are removed at variable intensity and spatial configuration across the landscape, retains greater forest structural heterogeneity than traditional clear-cut harvesting and is being recommended as an alternative for sustainable management of the boreal forest. Little is known about its effects on forest fauna; thus, we studied the influence of one type of VRH (harvesting with advanced regeneration [HARP]) on the Syrphidae (Diptera) community in northern Ontario forests of peatland black spruce (Picea mariana). We examined the effects of varying structural retention (from unharvested through partial retention to clear-cut) on syrphid species richness and abundance, and abundance of functional assemblages. Greater species richness and population abundances were found generally in harvested than in unharvested forests. Overall species richness and the abundance of four species (Platycheirus rosarum, Toxomerus marginatus, Xylota annulifera, and X. tuberculata) and larval predators were all higher in both clear-cut sites and those with structural retention than in unharvested sites. Similarly, overall species richness and the abundance of nine species were higher in clear-cut than in unharvested sites. Species responses are discussed in an ecological context. Differences among the levels of forest retention harvesting were relatively minor compared with those of the clear-cut and unharvested area, suggesting that local habitat characteristics may play a more important role in determining the syrphid community than the landscape configuration. However, a landscape level effect was evident, suggesting that syrphids may be useful in reflecting changes in stand structure at the landscape scale.

The exotic coccinellid Harmonia axyridis (Pallas) recently expanded its range into eastern Canada and elsewhere in North America. We hypothesized that this coccinellid should be less well adapted to the prey Mindarus abietinus Koch. on balsam fir trees than the native coccinellid Anatis mali (Say), which evolved in close association with aphids on conifers in North America. We compared, under field conditions, prey use by both species by collecting data on their synchrony with M. abietinus, their prey searching and predation behaviors, life stage distribution in fir canopy, and their overall reproductive success in this system. The seasonal life cycle of A. mali was better synchronized with that of M. abietinus compared with that of H. axyridis. In spring, A. mali adults appeared nearly 2 wk earlier on trees than H. axyridis and were active predators of the aphid fundatrices. A. mali oviposition thus began before the aphid population started to grow, and its larvae were most active during peak aphid colonies. Behavioral observations showed that both adults and larvae of the native A. mali searched for prey more actively than those of H. axyridis. Distribution of life stages also showed that eggs and pupae had different distributions on trees and that the adult-to-adult net reproductive rate of A. mali was three times higher than that of H. axyridis. Thus, the native A. mali was better adapted than H. axyridis to prey on M. abietinus, possibly because it evolved for a much longer period of time with this prey in conifer habitats.

Research on how morphology, behavior, and life histories of insects determine their susceptibility to parasitism has primarily focused on the traits of single host species. Very little research has been conducted attempting to determine if similarities or differences in the traits of co-occurring species, on a single plant or in a habitat, influence levels of parasitism imposed on any member of an assemblage. In this study, we use categorical and regression tree analyses to determine which traits of the larvae of macrolepidopteran species are associated with highest levels of parasitism. Of a variety of morphological, behavioral, and ecological traits of 72 species (representing eight families), caterpillar color was the trait that had the greatest influence on susceptibility to parasitism. The highest levels of parasitism were associated primarily with green larvae. These results suggest that the herbivore species composition and, specifically, the traits possessed by the species may influence community or assemblagewide patterns of parasitism. That is, sharing of traits that enhance host finding and successful parasitism may result in associational susceptibility to parasitism, whereas co-occurrence with species that differ morphologically, behaviorally, or ecologically may reduce the likelihood of parasitism and thus result in associational resistance. The concepts of associational resistance and susceptibility have historically been restricted to plant–plant interactions. The extension of these concepts to herbivores is novel. If found to be widespread, these interactions can have significant impacts on our expectations of the effectiveness of biological control agents.

The recovery of ant communities at the Guadiamar River bank (southwest Spain) was studied across 5 yr, after an environmental disaster caused by the spill of toxic sludge over the river caused by a mine accident. Three affected and three control sites were sampled from 2000 to 2004 using pitfall traps. The last year of study, a more exhaustive sampling was conducted at the affected area (eight sampling sites). Additionally, four adjacent study sites not affected by the toxic spill were also studied. Ants showed clear responses to the restoration of the area. Mean ant species richness in spillage affected sites showed a significant increase over the 5 yr. Moreover, multivariate analysis showed distinct changes of ant community composition of the affected area over the years that were not observed in control sites. Six years after the disaster, one half of the species recorded in control sites were also present in the affected area, with only one species exclusive to this area, Cardiocondyla mauritanica Forel (tramp species). However, not only habitat specialist species but also some generalist and conspicuous species within the river basin are not present along the affected area, including species of the genera Camponotus, Messor, Cataglyphis, and Aphaenogaster. This study shows an incipient recovery of ant communities 6 yr after a major environmental disturbance, highlighting the absence of any invasive ant species in the restored area.

This paper studied the occurrence of carabid beetles (Coleoptera: Carabidae) in the forest edge, the adjacent forest interior, and the surrounding grassland in southwestern China. Beetles were collected with pitfall traps along five replicated transects. Forest species rarely penetrated into the grassland from the forest interior, and the grassland specialists were not found in the forest interior. The forest edge hosted additional species from the adjacent grassland that increased its overall species richness. Nearly all forest species (23 of 24 species) and grassland species (13 of 15 species) can be found in the forest edge. Carabids of the forest edge were more similar to those of the forest interior than to those of the grassland by ordination and cluster analysis. Based on the specificity and fidelity, carabids can be distinguished into five species groups: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Multiple linear regression analysis showed that canopy cover and/or shrub cover were the most important factors in determining the richness, abundance, and diversity of carabids. The forest edge may serve as a transition zone for dispersal and re-colonization of carabid beetles from adjacent habitats and therefore is important for natural conservation.

The effects of tillage regimen (conventional [CT] and no-tillage [NT]) on the activity density and diversity of carabid beetles (Coleoptera: Carabidae) was studied by pitfall trapping within a rain-fed cropping system in northwestern Idaho, 2000–2002. The cropping rotation consisted of a spring cereal (barley, Hordeum vulgare L., in 2000 and 2001; and wheat, Triticum aestivum L., in 2002), spring dry pea (Pisum sativum L.) 2000–2002, and wheat (T. aestivum), spring in 2000 and 2001, and winter in 2002. A total of 14,480 beetles comprised of 30 species was captured, with five numerically dominant species [Poecilus scitulus L., Poecilus lucublandus Say, Microlestes linearis L., Pterostichus melanarius Ill., and Calosoma cancellatum (Eschscholtz)], accounting for 98% of all captures. All species including the dominants responded idiosyncratically to tillage regimen. Adjusting for trapping biases did not significantly change seasonal activity density of Poecilus spp. or Pt. melanarius to tillage. More beetles were captured in CT than in NT crops because of the dominance of P. scitulus in CT, whereas species richness and biological diversity were generally higher in NT crops. Observed patterns suggest that direct effects of tillage affected some species, whereas indirect effects related to habitat characteristics affected others. CT may provide habitat preferable to xerophilic spring breeders. A relationship was found between beetle species size and tillage regimen in pea and to a lesser extent across all spring crops, with large species (>14 mm) conserved more commonly in NT, small species (<7 mm) in CT, and intermediate species (7–14 mm) conserved equally between tillage systems.

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7°C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower (≈1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. The intrinsic rate of natural population increase (r), net reproductive rates (R_o), gross reproductive rate (Σm_x), generation time (T), doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated by life table analysis at 0.1155/d, 15.25 eggs per female, 21.69 eggs per female, 23.6 d, 6.0 d, and 1.1225/d, respectively. Because the r value of F. acarisuga is relatively lower than that of T. urticae, frequent release of F. acarisuga may be necessary to suppress populations of T. urticae.

The reproductive biology of Fidiobia dominica Evans (Hymenoptera: Platygastridae) was studied in the laboratory (25.6 ± 1°C) using host eggs of Diaprepes abbreviatus L. (Coleoptera: Curculionidae). F. dominica readily parasitized D. abbreviatus eggs on both host plant and wax paper substrates. The number of egg masses parasitized and the number of offspring produced were higher when females were offered more than one host egg mass but did not differ when either two or three egg masses were offered. Female parasitoids that were provided with host eggs and a honey food source lived significantly longer than those that were not provided a food source; however, they did not parasitize more D. abbreviatus eggs. Oviposition occurred in host eggs from 0 to 7 d old, and host mortality was relatively consistent for eggs 0–5 d old and lower for eggs 6–7 d old. Successful parasitoid emergence seldom occurred after host eggs were 4 d old, and by 7 d, no adults successfully emerged. Developmental time from egg to adult was 19.3 ± 0.2 d for males, significantly more rapid than the females (20.4 ± 0.1 d). The mean longevity of adult females was 8.0 ± 0.4 d, with a mean oviposition period of 2.7 ± 0.3 d; males survived 8.1 ± 0.4 d. The demographic parameters including intrinsic rate of increase (r_m), generation time (T), and net reproduction (R_o) were 0.142/d, 22 d, and 22.4 female eggs/d, respectively.

Extrafloral nectaries (EFNs) in many plant species produce sugary secretions that commonly attract ants. This research determined the impact of peach (Prunus persica L. Batsch) EFNs on the biological control of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a key economic pest in peach orchards, and studied interactions of EFNs and ants. Studies (2002–2005) in peach orchards of the mid-Atlantic United States showed that ‘Lovell’ peach trees with EFNs supported more parasitic Hymenoptera in the spring and increased the parasitism of G. molesta larvae later in the season than those trees without EFNs. Ant exclusion experiments revealed that trees with EFNs harbored fewer G. molesta larvae when ants were permitted access to the tree canopies. Furthermore, the trees with EFNs had ≈90% less fruit injury by G. molesta, indicating that EFNs have a protective role for the fruit as well. The results show that the combined actions of ants and parasitic Hymenoptera confer an EFN-mediated protective effect spanning the whole fruit growing season. When EFNs are present, naturally occurring biological control agents can reduce damage by G. molesta in peach orchards without insecticide inputs. The EFNs are an important host-plant characteristic that should be retained in future peach cultivar selections as a means of enhancing biological control.

Naïve adults and larvae of the native lady beetles Coleomegilla maculata (DeGeer), Cycloneda munda (Say), Hippodamia convergens Guérin-Méneville, Olla v-nigrum (Mulsant), and the exotic lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) were tested for their initial response to eggs of these five lady beetle species and for egg consumption on first contact and after 3 h. Additionally, field-collected O. v-nigrum and H. axyridis adults were tested. C. maculata, H. axyridis, and O. v-nigrum adults responded similarly to all egg species on first contact. Higher numbers of C. munda adults did not eat C. maculata, H. convergens, and O. v-nigrum eggs on first contact compared with numbers that did eat C. munda and H. axyridis eggs. H. convergens adults always ate C. munda eggs but hardly ate H. axyridis eggs on first contact. Results showed that over the 3-h interval, egg predation by those predators feeding on first contact was always higher, except for adults and larvae of C. maculata, than for those that did not feed on first contact. Thus, acceptance of eggs on initial contact does impact egg survival. It is likely that eggs of all native species tested (i.e., C. maculata, C. munda, H. convergens, and O. v-nigrum), but not exotic H. axyridis eggs, are suitable food for C. maculata, H. convergens, and O. v-nigrum, whereas only C. munda eggs serve as suitable food for C. munda. In direct contrast, all egg species tested would likely serve as suitable food for the exotic H. axyridis.

The megachilid bees Osmia lignaria Say, Megachile rotundata (F.), and M. pugnata Say were tested for attraction to various components associated with their old nest cavities, or chemical extracts of these components, using a Y-tube olfactory response bioassay. Female bees of these species are known to nest in or near old nest cavities, implying that remnant nest components are important cues for bees looking for nest cavities. Significant results show that female bees were attracted to components that may provide species-specific cues or indicate conspecific nesting activity. Specifically, O. lignaria females showed attraction only to the female cocoon. M. rotundata females were attracted to intact nest cells, the fecal material on the outside of a cocoon, leaf pieces used as nest cell lining, and the extract of leaf pieces. M. pugnata females were attracted to the whole nest cell, the paper straw nesting material with attached cocoon, and feces.

Field observations suggested that the introduced Hydrilla verticillata (L.f.) Royle biological control agent, a stem weevil, Bagous hydrillae O’Brien, would feed on hydrilla tubers and stems, and a native species, Bagous restrictus LeConte, would feed on hydrilla stems. In choice tests, B. hydrillae readily oviposited in hydrilla tubers. Larval development of B. hydrillae in hydrilla tubers was similar to that in stems; greater adult biomass was attained and less time was needed to complete development when the larvae were fed tubers. Larvae of the hydrilla tuber weevil, B. affinis Hustache, did not complete development in hydrilla stems. Larvae of B. affinis completed development more rapidly when fed new compared with old hydrilla tubers. The native B. restrictus successfully completed development in hydrilla stems, although the larvae required slightly more time compared with the biocontrol agent, B. hydrillae. These findings indicated that feeding on tubers by B. hydrillae may benefit the species particularly when hydrilla stems are seasonably absent or unsuitable especially in more northern climates. In terms of hydrilla control, damage to tubers by this species constitutes a reduction in future infestations of hydrilla propagated by tubers. Finally, hydrilla is suitable to the native weevil, B. restrictus, because larvae completed development in hydrilla stems.

Despite evidence for biological control in North America, outbreaks of the invasive soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), continue to occur on soybean (Glycine max L. Merr.). Our objectives were to determine whether natural enemies delay aphid establishment and limit subsequent population growth and whether biological control can be improved by altering the within-field habitat. We hypothesized that a living mulch would increase the abundance of the aphidophagous community in soybean and suppress A. glycines establishment and population growth. We measured natural enemy and A. glycines abundance in soybean grown with and without an alfalfa (Medicago sativa L.) living mulch. Soybean grown with an alfalfa living mulch had 45% more natural enemies and experienced a delay in A. glycines establishment that resulted in lower peak populations. From our experiments, we concluded that the current natural enemy community in Iowa can delay A. glycines establishment, and an increase in aphidophagous predator abundance lowered the rate of A. glycines population growth preventing economic populations (i.e., below the current economic threshold) from occurring. Incorporation of a living mulch had an unexpected impact on A. glycines population growth, lowering the aphids’ intrinsic rate of growth, thus providing a bottom-up suppression of A. glycines. We suggest future studies of living mulches or cover crops for A. glycines management should address both potential sources of suppression. Furthermore, our experience suggests that more consistent biological control of A. glycines may be possible with even partial resistance that slows but does not prevent reproduction.

The influence of trap placement on catches of codling moth, Cydia pomonella L., was examined in a series of studies conducted in orchards treated with Isomate-C Plus sex pheromone dispensers. Mark–recapture tests with sterilized moths released along the interface of pairs of treated and untreated apple and pear plots found that significantly more male but not female moths were recaptured on interception traps placed in the treated plots. In a second test, significantly higher numbers of wild male and female moths were caught on interception traps placed in treated versus untreated plots within a heavily infested orchard. The highest numbers of male moths were caught on traps placed along the interior edge of the treated plots. Trap position had no influence on the captures of female moths. In a third test, north–south transects of sex pheromone–baited traps were placed through adjacent treated and untreated plots that received a uniform release of sterilized moths. Traps on the upwind edge of the treated plots caught similar numbers of moths as traps upwind from the treated plots. Moth catch was significantly reduced at all other locations inside versus outside of the treated plots, including traps placed on the downwind edge of the treated plot. In a fourth test, five apple orchards were monitored with groups of sex pheromone–baited traps placed either on the border or at three distances inside the orchards. The highest moth counts were in traps placed at the border, and the lowest moth counts were in traps placed 30 and 50 m from the border. In a fifth test, the proportion of traps failing to catch any moths despite the occurrence of local fruit injury was significantly higher in traps placed 50 versus 25 m from the border. The implications provided by these data for designing an effective monitoring program for codling moth in sex pheromone–treated orchards are discussed.

The effects of season and community composition as generated by livestock herbivory of differing intensity on seed species preference by Pogonomyrmex barbatus (F. Smith) were studied in a semiarid savanna on the Edward’s Plateau, TX. Seasonal differences in nutrient requirements of the colony could lead to differential preferences for seeds harvested in spring and fall. Field cafeteria studies were conducted to test the hypothesis that late successional species, with their high nutrient content, would be chosen regardless of grazing intensity or season. Commercial seeds of known nutrient content were used to test the hypothesis that high protein levels would be chosen in spring and high carbohydrate levels in the fall. Naturally occurring seeds were differentially harvested and some were preferred regardless of relative availability. Total seed harvest in cafeteria experiments was higher in spring than in fall. Commercial seeds were harvested equally among treatments within a season; thus, nutrient selection was indistinguishable. Preference for native species was significantly different in both seasons but was influenced by a significant interaction with grazing treatments. Bouteloua curtipendula, a late successional mid-grass, was harvested significantly more in the spring than the fall and at higher rates in the heavily grazed treatment, rejecting the hypothesis that they would be chosen regardless of treatment or season. Seed preference for late successional grasses within heavily grazed communities may slow succession after grazing. During disturbance recovery, late successional species may be reduced by forager preference and rates of spring harvest.

This study assessed the influence of microenvironment on the establishment and relative reproductive success of the gall-forming midge Rhopalomyia californica Felt on its host plant Baccharis pilularis De Candolle in Marin County, CA. Mesh cages were used to alter the microenvironment, which also allowed us to assess the validity of using these types of experimental manipulations in this system. Temperature, light intensity, wind speed, and stem growth were compared in caged and uncaged B. pilularis plots in two sites during three seasons. Cage presence significantly altered the microenvironment of R. californica but did not affect development. R. californica establishment was greater when growing on host plants with increased stem growth. Season had the largest impact on gall establishment and reproductive success, with the highest establishment and success rates in late winter to early spring, which correlated with the growing period of B. pilularis. These results suggest that the seasonality of R. californica reproductive success is linked to the phenology of its host plant. When the growing conditions for the plant are less than ideal, R. californica performance is stimulated by increased stem growth. Cage presence was not a significant driver of population dynamics because it did not change the environment in an ecologically meaningful way. We therefore assert that the use of cages for experimental manipulations in this study system does not alter R. californica performance.

An aggressive, non-native haplotype (distinct genetic lineage within a species) of Phragmites australis is invading brackish and freshwater systems in the eastern United States, potentially displacing native haplotypes. We studied the differential susceptibility of native and non-native populations collected from sites throughout North America to the non-native aphid, Hyalopterus pruni. In a greenhouse study, we found significantly higher aphid populations on native haplotypes than on the non-native haplotype 2 mo after infestation. Aphid feeding caused chlorosis and death of native stems, and in some cases, killed whole native genets. The non-native plants remained relatively undamaged. In a field study, non-native plants had significantly lower aphid densities than native plants or remained aphid free. There was an interactive effect in which aphid populations increased on the native plants over the 1-mo study period but remained low on non-native plants over the same period. The susceptibility of native North American populations of P. australis to non-native aphid infestation may indirectly affect the ability of these native plants to compete with non-native plant populations, ultimately contributing to the decline of native haplotypes.

The Mi resistance gene in tomato reduces the feeding, fecundity, and survival of certain isolates of the potato aphid (Macrosiphum euphorbiae Thomas). This study compared the performance of two potato aphid isolates, WU11 and WU12, on nearly isogenic susceptible (Mi−) and resistant (Mi ) tomato cultivars. Although Mi significantly reduced the population growth of both aphids, WU12 numbers decreased by only 15% compared with 95% for isolate WU11. These results show that there are quantitative differences in virulence among potato aphid isolates. Compared with WU11 aphids, isolate WU12 caused more necrosis on both resistant and susceptible plants, and this increased damage may play a role in the partial virulence of isolate WU12. However, infestation with aphid isolate WU12 did not compromise plant defenses against isolate WU11 in resistant plants. Prior inoculation with either aphid isolate caused a modest reduction in the survival of WU12 adults, but this form of induced resistance was observed on both resistant and susceptible cultivars. Thus, Mi did not play a role in acquired resistance or mediate any indirect interactions between the two aphid isolates. Notably, the mode of action of Mi-mediated resistance seemed to differ depending on the aphid isolate tested. Mi dramatically deterred feeding by WU11 aphids, whereas the effects of resistance on isolate WU12 seemed to be caused primarily by antibiosis. Tolerance did not seem to be a major component of Mi-mediated responses, although resistant plants showed a modest reduction in the amount of foliar necrosis induced per aphid compared with susceptible plants.

Studies on strategies of host plant use in sympatric-related species are significant to the theory of sympatric speciation. Altica fragariae Nakane and Altica koreana Ogloblin are sympatric closely related flea beetles found in Beijing, northern China. All their recorded host plants are in the subfamily Rosoideae of the Rosaceae, so we regard them as a model system to study interactions between herbivorous insects and plant-insect co-evolution. We conducted a set of experiments on the host preference and performance of these flea beetles to study whether these closely related species have the ability to use sympatric novel host plants and whether monophagous and oligophagous flea beetles use the same strategy in host plant use. Oviposition preference experiments showed that A. koreana, a monophagous flea beetle, displayed high host fidelity. However, A. fragariae, which is oligophagous, often made “oviposition mistakes,” ovipositing on nonhost plants such as Potentilla chinensis, the host plant of A. koreana, although normal host plants were preferred over novel ones. Larval performance studies suggested that A. fragariae was able to develop successfully on P. chinensis. Feeding experiences of larvae had no effect on feeding preference, oviposition preference, and fecundity of adults. However, females were impaired in their reproductive ability when fed on nonhost plants. Therefore, A. fragariae finished their development of larval stages on P. chinensis and came back to their primary host plant, Duchesnea indica, for feeding and reproduction after eclosion.

Modeling the effect of temperature on the sustainability of insect–plant interactions requires assessment of both insect and plant performance. We examined the effect of temperature on western flower thrips, Frankliniella occidentalis (Pergande), a generalist herbivore with a high reproductive rate, and chrysanthemum inflorescences, a high quality but relatively fixed, ephemeral resource for thrips population growth. We hypothesized that different thrips versus plant responses to temperature result in significant statistical interaction of temperature with thrips abundance and flower damage attributes over time. Experiments were conducted at five temperatures between 20.7 and 35.3°C, with thrips infestation and time after infestation as main effects. Only minor, uncontrolled variations in relative humidity and light intensity may otherwise have influenced the results. High temperatures lead to an initially rapid increase in density of thrips followed by abrupt declines in abundance. The rate of floral senescence increased with temperature and thrips infestation, as indicated by a reduced fresh biomass and greater leaching of yellow pigments. Multiple regression indicated that indices of plant damage responded more directly to thrips density at low than high temperature, supporting the conclusion that temperature affected the outcome beyond what was predictable simply from differential plant and insect optima. The relative intensity of damage caused by individual thrips decreased with increasing temperature, likely caused by thrips competition and reduced survival, growth, and fecundity on depleted inflorescences. Reduced per capita damage at high temperature may be common in insects exploiting fixed plant resources that exhibit an accelerated rate of deterioration at high temperatures.

A clinal female flight polymorphism exists in the gypsy moth, Lymantria dispar L., where female flight diminishes from east to west across Eurasia. A Russian population where females are capable of sustained ascending flight and a North American population with females incapable of flight were crossed: parentals, reciprocal F₁ hybrids, double reciprocal F₂ hybrids, and all possible backcrosses to both the parental lines were compared. Heritabilities were estimated using a threshold model, female offspring on female parent regressions, and joint-scaling analyses. Heritability of female flight capability measured using a free flight test was at least 0.60, and variation in wing size, muscle strength, and flight behaviors contributed to the flight polymorphism. Relative wing size varied continuously and had a heritability of 0.70. Environmental variation accounted for >90% of the variation in female preflight weight and relative flight muscle strength, as estimated by an inverted female’s ability to right herself. Preflight walking behavior and early deposition of eggs were each inherited through a single gene with two co-dominant alleles. There was no evidence for sex-linkage or maternal effects in female flight capability or associated traits. Continued vigilance to exclude and eradicate introductions of strains capable of female flight in North America is warranted even in areas where no females fly, because some of the alleles needed for full flight capability may not be present in the North American populations, and some flight capability is maintained in the hybrids that could increase the rate of spread of L. dispar.