In this article, we describe a hybrid zone between the chrysomelid beetles, Chrysochus auratus (F.), and C. cobaltinus LeConte, which have historically been considered as having allopatric distributions. By combining field studies with surveys of museum specimens, we documented that in western North America there are two regions in which these beetles are sympatric, and four additional regions in which populations of the two species are <100 km apart. In south-central Washington, we found an ≈25 km wide area of sympatry in which the two species freely interbreed. Morphological and allozyme differences between the species allowed us to demonstrate that individuals with intermediate coloration in this area are indeed hybrids; all 22 putative hybrids we assayed for allozyme variation were heterozygous at each of three species-specific loci. Museum specimens revealed that the two species have been hybridizing in this region at least since 1952. Within the hybrid zone, ≈10–15% of the beetles is apparently F₁hybrids. At one focal site, 22.9% of all matings involved heterospecific pairs and 20.8% of all matings involved at least one hybrid individual. Although we found no molecular evidence of introgression between the two species, morphometric results and preliminary ecological data suggest possible past introgression or weak ongoing introgression. We discuss the implications of our findings for the specific status of these two species. This system appears well suited to provide answers to long-standing questions concerning the evolution of premating barriers between hybridizing species. In addition, hybridization between these two beetle species with differing host ranges will allow us to test the hypothesis that ecologically significant traits such as diet breadth can be gained via introgression.

A larval argasid tick (Acari: Ixodida: Argasidae) is described from a single specimen preserved in amber from New Jersey. The amber is dated as Turonian, 90–94 mya, and thereby doubles the age of the oldest fossil in the mite order Parasitiformes. The specimen shows general characteristics of the genus Carios, but is unique because of its pattern of dorsal setae, featuring a double row of posterior marginal setae. Earlier hypotheses that Carios arose after the isolation of South America are challenged but not rejected by the discovery of this fossil. Salvaging these hypotheses seems most compatible with dispersal on birds, an idea consistent with the presence of a small feather in the same outcrop in which the tick fossil was found.

Two new species, Drosophila huckinsi Etges & Heed and D. huichole Etges & Heed from Mexico are described and compared with close relatives in the D. longicornis cluster of the large D. repleta group in the subgenus Drosophila.

Dendroctonus pseudotsugae barragani is described as new to science from the Sierra Madre Occidental Mountains in Chihuahua, Mexico. It differs from the nominate subspecies in 10 anatomical features involving the head, pronotum, and elytral declivity and in the manner in which groups of eggs are laid. Cross-mated male and female beetles from Chihuahua and Idaho produced 67% fewer progeny than did pairs of beetles from either locality. Further evidence of isolation of the Mexican population is shown by differences in the species of entomophagous and scolytid insects associated with the two subspecies of D. pseudotsugae.

Limnocoris lutzi La Rivers occurs from the southern side of the mountain spine in Chiapas, Mexico, north through eastern Mexico to central Texas. Its voltinism was studied in the South Llano River in central Texas in 1988 and 1989. This species overwinters as adults among rocks and sand in riffles and is univoltine in central Texas. Adults are present year-round and nymphs occur from early May through mid-November. Eggs have two distinct micropyles and many aeropyles, but are devoid of other chorionic protruberances. The chorionic outer layer is perforated by pore canals that extend perpendicularly to the imperforate chorionic inner layer. This species has five instars, the first of which differs from the remainder in basic color pattern. Eggs and all instars were examined with light and scanning electron microscopy and are illustrated and described.

The impact of different densities of Allegheny mound ant, Formica exsectoides Forel, populations on myrmecophilous (tended) and nonmyrmecophilous (untended) aphid and scale species and their potential predators was examined in jack pine forests of north-central Michigan. A summer-long survey indicated that areas with large populations of F. exsectoides had larger populations of the aphid Cinara banksiana Pepper & Tissot and the soft scale Toumeyella parvicornis (Cockerell), two obligate myrmecophiles, than areas with low or no F. exsectoides populations. Cinara ontarioensis Bradley was also obligately tended by ants but did not show a significant response to F. exsectoides densities, having a patchy distribution. In contrast, in areas without F. exsectoides, these homopterans were replaced by the woolly aphid Schizolachnus piniradiatae (Davidson), a species that never forms ant associations. Mound ant exclusion experiments and observations indicated that F. exsectoides preyed upon S. piniradiatae, potentially reducing their numbers in areas with this ant. Aphid and scale predators showed a mixed response to F. exsectoides presence: densities of lacewing larvae and salticid spiders were inversely related to F. exsectoides populations, whereas mirid populations did not show a response to different F. exsectoides densities. This study suggests that the presence of large populations of aggressive, honeydew seeking F. exsectoides can shift the homopteran community from one composed predominantly of nonmyrmecophilous species to one composed of myrmecophilous species.

The phenology and population dynamics of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), were studied from 1991 to 1995 using Jackson traps baited with trimedlure and periodic fruit sampling in two orchards in Thessaloniki northern Greece (40.3° north latitude, 22.5° longitude). This area is located within the northernmost zone of establishment of the fly in Europe. No adults were captured from December to the end of June. The first captures were recorded from the end of June to August, depending on the year and orchard, and captures rates peaked in the autumn of each year. Significant differences were observed in adult population density and in the initiation of fly activity between two neighboring orchards (≈500 m apart) that differed in host fruit abundance and availability. The results of fruit sampling showed that apricots were the first fruits infested every year in the area of Thessaloniki. Though infested at low rates, they were very important for breeding the first summer generation, and also for the increase in C. capitata population later in the summer. Peaches and figs were important hosts for breeding the late summer and early autumn generations. Apples and other pome fruits were important hosts later in autumn (October–November), and also served as overwintering refuges for the larvae. Among 17 fruit species collected in the area 11 were found infested. Pecan [ Carya illinoensis (Wang) k. Koch] and Malus floribunda Sieb. (an ornamental tree) are reported here for the first time as hosts of C. capitata. Our findings suggest that C. capitata completes four to five generations per year in the area of Thessaloniki. Practical and theoretical implications concerning the population dynamics and the control of this fly are discussed.

A phylogenetic analysis was conducted of the Anthonomus grandis species group (Coleoptera: Curculionidae) and used to test various hypotheses concerning the evolution of these weevil species with their host plants. Phylogenetic analysis indicated that the five species of the A. grandis species group comprise two major clades. In the first clade, A. grandis Boheman is the sister taxon of A. hunteri Burke & Cate and A. mallyi Jones & Burke, and the second clade contains A. townsendi Jones & Burke and A. palmeri Jones & Burke. The proposed weevil phylogeny and knowledge of host associations strongly support the hypothesis that the genus Hampea (Malvales: Malvaceae), and not cotton ( Gossypium), is the original host plant genus of the A. grandis species group. Comparison of the phylogeny of the A. grandis group with that of a previously published phylogeny of Hampea showed little congruence, suggesting that the species of weevils are associated with Hampea as a result of host shifts and colonization processes, as opposed to co-speciation or coevolution (parallel cladogenesis). Mapping habitat associations and geographic distributions onto the phylogeny of the A. grandis group indicate that weevil preference for general habitat type (montane versus lowland habitats) and geographic proximity of species of Hampea were probably the principal factors responsible for observed associations of the weevils with their respective host plants. Possible characteristics of the A. grandis group, which may favor colonization as opposed to cospeciation processes in the association of its host plants, are discussed in light of these results.

We examined the spatial pattern of the ant Myrmecocystus mexicanus Wesmael. Although intraspecific dispersion is highly uniform, colonies were significantly associated with reproductively mature nests of the harvester ant Pogonomyrmex occidentalis (Cresson). Colonies of M. mexicanus were more likely to be found within 3 m of P. occidentalis and less likely to be found as far as 10 m away. The protein component of the diet of M. mexicanus at this site is almost exclusively dead or moribund workers of P. occidentalis. M. mexicanus appears to associate with one of its consistent food sources.

The hemlock woolly adelgid, Adelges tsugae Annand, is a major threat to hemlocks in the eastern United States. As part of efforts to control this pest, Scymnus ( Neopullus ) sinuanodulus Yu et Yao, a potential predator, was collected from hemlocks in Yunnan, China. Three shipments were imported during 1996 and 1997 to a quarantine laboratory to study the beetle’s biology. Beetles began oviposition immediately after transferal from 5°C in the spring, ceased oviposition by June, and laid the same number of eggs, whether egg laying began in February or in April. Two-year-old beetles laid as many eggs per year as 1-yr-old beetles. We observed only one generation per year. Yearly fecundity averaged 130 eggs with a maximum of 200 per female. Newly emerged beetles remained preovipositional until the following spring, but could be induced to oviposit in the fall by prior exposure to 5 or 10°C for 1.5 mo. The egg, larval (four instars), and pupal stages lasted 10, 20, and 10 d, respectively, at 20°C. From egg to adult took 73, 40, and 35 d at 15, 20, and 25°C, respectively. Larval survival was only 5% at 25°C. Both larvae and adults fed on all stages of A. tsugae, but larvae grew faster with much higher survival on adelgid eggs, and could not complete development on adelgid nymphs alone. When given adelgid eggs, the beetles laid more eggs initially; however, adelgid nymphs seem to satisfy nutritional requirements for oviposition. Laboratory-reared beetles were similar to field-collected beetles in oviposition, fecundity, feeding, survival, and development.

Wild radish is an annual plant that exhibits broad spectrum induced resistance to herbivores. In two experiments, we placed potted plants [control, manually clipped, and damaged byPieris rapae(L.) larvae] in the field and assayed for oviposition byP. rapae(a specialist herbivore), damage by flea beetles (a specialist herbivore), and damage by rabbits (a generalist herbivore). Induced responses attracted oviposition byP. rapaeand increased damage by flea beetles, while having a minimal effect on rabbit herbivory. Plant families had different levels of resistance to herbivory by rabbits and to oviposition byP. rapae,but not to herbivory by flea beetles. Manual clipping was a poor inducer of plant responses. Induced responses in wild radish can be a double-edged sword, increasing herbivory by some herbivores under certain conditions, while reducing herbivory by other herbivores.

Adult and larval aphidophagous lady beetles (Coleoptera: Coccinellidae) feed on alfalfa weevil larvae, Hypera postica (Gyllenhal), and aphids in alfalfa fields. We studied the development of first and fourth instars of two lady beetle species ( Coccinella septempunctata L. and Harmonia axyridis Pallas) when provided live or dead weevil larvae versus pea aphids, Acyrthosiphon pisum (Harris). No individuals of either species survived to the second stadium on a diet of weevils (dead or alive), whereas almost 100% of first instars of both species did so on a diet of aphids. Nearly all individuals of H. axyridis that were provided weevils (dead or alive) during the fourth stadium survived and subsequently completed pupation. However, these individuals weighed significantly less as newly molted adults than did conspecifics that had fed on aphids as fourth instars. Only 5% of fourth-instar C. septempunctata survived to adulthood when provided live weevils (versus 100% provided aphids), but 70% did so when provided dead weevils. Both first and fourth instars of both species attacked both dead and live weevil larvae much less readily than aphids, and were often deterred from persisting in the attack by the defensive wriggling of live weevil larvae (in contrast to their persistence and success in attacking aphids). Nevertheless, even first instars of the predators succeeded in some instances in overcoming weevil larvae, and proceeded to feed upon the prey for up to the maximum of 10 min of observation. Our results suggest that although weevil larvae are not very suitable as substitute prey for aphids for the larvae of C. septempunctata and H. axyridis, consumption of weevil larvae especially by older larvae of the predators (particularly H. axyridis) may enable them to complete development in alfalfa fields even when aphid populations fall to low levels.

The supercooling points (SCP) of immature stages and adults as well as survival of adult females after exposure to subzero temperatures were studied in a strain of the predatory mite Euseius finlandicus (Oudemans) from northern Greece. The mean SCP of eggs was −27.6°C. The mean SCPs of different immature stages fed on pollens of Papaver rhoeas L. or Typha sp. enriched with β-carotene were similar and varied from −21.1 to −24.7°C. The mean SCPs of diapause females acclimated for 2 wk at 5°C or not acclimated, nondiapause females and males fed on pollens of P. rhoeas and Typha sp. were similar and varied from −22 to −24.3°C. When groups of diapause females were exposed temporarily to different subzero temperatures, the temperature-mortality curve followed the distribution of the SCPs, which indicates that the SCP is the lower limit of survival. More than 80% of the diapause females died when exposed for 20 min to −15°C, a temperature well above the SCP which indicates that they suffered prefreeze mortality. They survived considerably longer durations of exposure to −15°C after a prior acclimation for 2 wk at different low temperatures. After certain acclimation treatments, diapause females that survived exposure to −15°C laid a similar number of viable eggs as those not exposed to subzero temperatures, which indicates that cold stress may not affect fecundity.

The behavior and biology of the aphidophagous hoverfly Pseudodorus clavatus (F.) were studied in the laboratory. The survival of P. clavatus larvae fed Aphis spiraecola Patch was 24% from egg to adult, not significantly different from larvae fed Toxoptera citricida (Kirkaldy) (36%). However, larval development was significantly faster on the T. citricida diet and the resulting adults were 50% heavier. Cannibalism of eggs and larvae was common among newly eclosed larvae independent of the presence of aphids, but not among older larvae. The adult sex ratio at eclosion was 0.485 (♀:♂) but 50% of females died before oviposition. Male flies lived for a mean of 16.8 ± 3.8 d and ovipositing females for 29.8 ± 1.9 d at 23°C. The prereproductive period for females averaged 6 d, and the majority of eggs were laid during morning hours, oviposition peaking between 0830 and 1030 hours. There was no preference among naïve females to oviposit near either aphid species and eggs were also laid on aphid-infested terminals containing conspecific eggs or larvae. Oviposition was elicited on plant tissues with aphids or residues of aphid honeydew but not on clean plant tissues. Samples of P. clavatus larvae collected from Aphis spiraecola on Viburnum spp. in winter in central Florida were heavily parasitized by the solitary parasitoid Eurydinotelloides bacchadis (Burks) (Hymenoptera: Pteromalidae).

Many approaches are being tested to control the red imported fire ant, Solenopsis invicta Büren. Biological control through the use of parasitoids and parasites is promising. Among the parasitoids of these ants, Pseudacteon spp. (phorid flies) are receiving special attention. One of these species, Pseudacteon tricuspis Borgmeier, has been released in target areas for field assessments. However, there is not enough information about their biology or interactions with their hosts. Here we describe the parasitization and development of P. tricuspis in two sizes of ants. We also evaluated the behavioral response of these ants to the attack of this fly. We found no difference in the development of P. tricuspis when attacking small or large ants. The immatures showed similar developmental time and morphology in both groups of ants. The egg is laid in the thorax, and there are three instars before pupariation. The first instar develops in the thorax, and it remains inside its serosa after hatching. It molts into a second instar soon after leaving its serosa. Second and third instars develop in the head. Pupariation takes place inside the head of the host. Adults eclose ≈19 d after pupariation. We also discuss some of the possible physiological mechanisms involved in the host–parasitoid interactions, as well as in the interactions with conspecifics. The feasibility of developing in vitro rearing systems to culture this parasitoid is also addressed.

We investigated the host range and preference of the high-mountain species Timarcha lugens Rosenhauer, an insect species with highly mobile larvae, testing the degree of specialization and the correlation between larval and adult preference for host plant. All 720 larvae, 1,035 adult females and 994 adult males, censused in the field over 3 yr (1997–1999) and in 20 populations located along all the distribution area of the species were living on one single host plant, Hormathophylla spinosa Küpfer (Cruciferae). This differs from other Old World Timarcha, which are adapted to feed on Plantaginaceae and Rubiaceae. Laboratory experiments confirmed these observational results; all 130 beetles tested fed only on H. spinosa, and no beetle accepted any other plant species either in choice or nonchoice experiments. Larval and adult preference proved identical, both stages selecting only H. spinosa. We suggest that T. lugens has evolved the ability to attack an atypical host.

The effect of photoperiod on preimaginal development and diapause induction (for reproductive diapause) was evaluated for two geographic populations of the predator Geocoris punctipes (Say). One population was from Lexington, KY (N38° 04′, W84° 29′), and the other from Tifton, GA (N31° 28′, W83° 31′). Six photoperiods were used in the experiment (all at 24 ± 1°C): 10:14, 11:13, 12:12, 13:11, 14:10, and 15:9 (L:D) h. Photoperiod and population had significant effects on the developmental times of embryos and nymphs. However, the developmental differences had no apparent relationship with photoperiod, and those between populations were slight (<1 d). The incidence of diapause increased for both populations as photoperiod decreased, but at daylengths shorter than 14:10 (L:D) h, the frequency of diapause increased much more steeply in the Kentucky population than in the Georgia one. At its peak, the incidence of diapause in the Georgia population (40.9%; 10:14 [L:D] h) was about half that of the peak of the Kentucky population (81.8%; 12:12 [L:D] h). Also, the critical photoperiod for diapause induction was ≈1 h longer in the Kentucky population than in the Georgia population. The preoviposition period was notably affected by photoperiod, and this effect differed between populations. Short daylengths prolonged the preoviposition period in both populations, but the contraction of the preoviposition period in response to longer daylength was more pronounced in the Georgia population. The considerable difference in diapause incidence between the two populations may reflect the relative predictability of inclement conditions in the respective locations.

A new method was developed to control adult chironomid midges, Chironomus plumosus (L.) and Einfeldia dissidens (Walker), using their acoustic responses to sound traps in the field. Trials were conducted in 1999 from 2 to 7 June (during emergence period of E. dissidens ) and from 2 to 7 September (emergence period of C. plumosus ) near hyper-eutrophic Lake Suwa in central Japan. Swarms of E. dissidens were formed at 1–3 m above the terrain and were observed from 1900 to 1930 hours. More than 97% of E. dissidens trapped from the swarms were males. In cylindrical sound traps, optimal trapping of swarming males occurred at a frequency of 240 Hz at 21.9 ± 2.3°C. Swarms of C. plumosus were formed at 1 m to >5 m above ground, and were observed from 1830 to 1900 hours. More than 88% of C. plumosus caught from the swarm were males, and optimal trapping of swarming males occurred at frequencies of 300–360 Hz at 20.7 ± 0.5°C. We compared our results with those of other chironomid species and attempted to clarify the relationship between female wing length and ambient air temperature. There was no correlation between the most attractive frequency and female wing length. However, a positive correlation existed between the most attractive frequency and air temperature. It is concluded that the most attractive frequency differed among species (interspecific) according to air temperature. These mechanisms may play an important role in isolation during chironomid swarming.

Observations were made on 26 Brazilian fireflies species of the genera Cratomorphus, Aspisoma, Photinus, Macrolampis, Bicellonychia, Pyrogaster, Photuris, Amydetes, Lamprocera, and Lucidota occurring in the eastern region of Sao Paulo State. These species are adapted to mesophyl tropical forests, secondary growths, marshy areas, and open fields. Cratomorphini larvae were often arboreal and preyed on snails and slugs. Cratomorphus sp₂and Aspisoma sp₂inhabited marshy areas and their larvae were natural enemies of the aquatic snails Biomphalaria tenagophila Orbigny and Stenophisa columella Say. Photurinae species inhabited marshy areas and humid woody environments and their larvae were always found at ground level. The entire life-cycle of Bicellonychia sp₈lasted 11 mo. Most adult fireflies were active for less than 1 h during humid and hot spring evenings, from October to December, although many species were found active during the August–April period. Wave-synchronized bioluminescent signals were observed in Bicellonychia sp₈. Glow patterns in the green region of the spectrum were predominant among forest dwelling fireflies, whereas flash patterns in the yellow-green and yellow region were more commonly observed among open-field dwelling fireflies. This trend may be adaptation to luminescent signal optimization in different photic environments or for different signal functions, such as sexual attraction, defense and illumination.

One potential biochemical adaptation to mixed feeding habits, or zoophytophagy, is enzyme induction/enzyme repression. We investigated the potential of the highly polyphagous mirid Lygus hesperus Knight to increase its production of the specialized proteolytic enzyme, elastase (E. C. 3. 4. 31.36). Efforts to induce elastase production were made by feeding L. hesperus on an artificial diet spiked with elastin. Short-term (less than one generation) and long-term (three generations) tests were conducted to determine the effect of acute versus chronic exposure to elastin, a protein that may be present in extra cellular matrix of prey. Elastase activity was much greater in the salivary gland complex (SGC) of individuals fed elastin-containing diet than it was in those fed the control diet. The elevated elastase activity in the elastin treatment group indicated the inducibility of this proteolytic enzyme, especially in the SGC. The results also indicated that the SGC, rather than the gut, is the principal site of elastase production.

The pteromalid parasitoid Pteromalus cerealellae (Ashmead) is nominally a host-specific ectoparasitoid of the stored-product pest the Angoumois grain moth. It is readily cultured, however, on a number of other stored-product pests, including the cowpea weevil. The parasitoids resulting from these different hosts are disparate in size, leading me to ask if the cuticular hydrocarbons of P. cerealellae reared on different hosts would be different. This question is of importance because many parasitoids of stored-product pests use cuticular hydrocarbons as major species- and gender-recognition cues, and moth and beetle hosts differ greatly in their hydrocarbon profiles. The parasitoid hydrocarbon profile reported here was much more complex than the profiles of either host and showed both gender and host effects. Parasitoids reared on the larger cowpea weevils were larger than those reared on moths and contained substantially more hydrocarbon on their cuticle. Regardless of host, female wasps were always larger than males and contained more hydrocarbon than males. The hydrocarbon chemistry of wasps reared on different hosts were qualitatively the same, but quantitatively different. Both gender and host are important in the relative abundance of individual hydrocarbons. There are four major hydrocarbons of females constituting 49% of the total female profile: 3-MeC₂₉, 11-MeC₃₁, 3, 7-DiMeC₃₁and 11, 17-, 11, 19- and 11, 21–DiMeC₃₃. There is one major male-specific hydrocarbon comprising 18% of the total hydrocarbons, 3, 7- and 3, 9–DiMeC₃₃. Although major gender differences occur between hydrocarbon classes, these differences are not host-related.