Field-collected Beetles Research Articles

A Preliminary Study on Flight Characteristics of the Longhorn Date Palm Stem Borer Jebusaea hammerschmidtii (Reiche 1878) (Coleoptera: Cerambycidae) Using a Computerized Flight Mill

The longhorn date palm stem borer, Jebusaea hammerschmidtii (Reiche), is a highly destructive beetle of edible date palm Phoenix dactylifera L. The flight capabilities and dispersal potential of this beetle are unknown, which hinders the planning for its proper management in date palm groves. In this study, the flight propensity of this insect pest was investigated using a computerized flight-testing system. The flight system consisted of a flight mill, a digitally controlled testing chamber, and a data logging and processing unit with a USB digital oscilloscope connected with a laptop. A total of 40 field-collected beetles of unknown sex and mating history were used in the experiments; about 34% of this number failed to fly on the flight mill. The relationship between temperature treatments (°C) and flight speed (m/min), cumulative flight time (min), and cumulative flight distance (km) of the test beetles were studied using regression equations with correlation coefficients (R2) of 0.91, 0.98, and 0.98, respectively. The maximum cumulative distance flown by the beetle was 11.5 km at a temperature of 35 °C, and a minimum distance of 2.4 km was recorded at 45 °C. The flight threshold of the beetle was 20 °C, at which flight activities ceased utterly. The velocity of the beetle increased with increasing temperature and reached a maximum of 107 m/min at 40 °C, before starting to decline. The obtained information on the flight characteristics of the J. hammerschmidtii may aid in understanding the dispersal of this pest in date palm plantations and in setting up management strategies.

Identification of Pheromone Components of Plagionotus detritus (Coleoptera: Cerambycidae), and Attraction of Conspecifics, Competitors, and Natural Enemies to the Pheromone Blend.

Simple SummaryThe longhorn beetle, Plagionotus detritus (L.), occurs throughout Europe and into the Middle East. Our principal aim was to identify the male-produced aggregation-sex attractant pheromone of this species. A pheromone-based monitoring system could support plant protection in areas where it might become a pest and natural conservation in areas where it is endangered. Headspace volatiles were collected from live beetles and analyzed by coupled gas chromatography-electroantennogram detection and gas chromatography-mass spectrometry. Two components of the extracts that elicited responses from antennae of P. detritus, (R)-3-hydroxyhexan-2-one and (S)-2-hydroxyoctan-3-one were identified, (±)-3-hydroxyhexan-2-one was purchased, and (S)-2-hydroxyoctan-3-one was synthesized, and field-tested. The blend of the two components attracted both sexes of P. detritus in field bioassays. Unexpectedly, a predatory clerid beetle, Clerus mutillarius F., was also attracted by both of the synthetic compounds. Another longhorn beetle species, Xylotrechus antilope Schönh. was significantly attracted to traps baited with (S)-2-hydroxyoctan-3-one alone or the blend containing this compound. These results show that the pheromone components and combinations play key roles in longhorn beetle life history and ecology, and the community of species in which they live.(1) Background: The principal aim of our work was to identify pheromone components for Plagionotus detritus (L.) (Coleoptera: Cerambycidae), which could be exploited for developing a pheromone-based monitoring system for the complementary purposes of plant protection in areas where it might become a pest, and natural conservation in areas where it is rare or endangered. (2) Methods: Collection and analysis of headspace volatiles were carried out with field-collected beetles. Bioactive volatile compounds identified [(R)-3-hydroxyhexan-2-one and (S)-2-hydroxyoctan-3-one] from extracts of males were purchased [(±)-3-hydroxyhexan-2-one], and synthesized [(S)-2-hydroxyoctan-3-one] and field-tested. Electroantennogram assays showed that antennae of the predatory beetle Clerus mutillarius F. (Coleoptera: Cleridae) also responded to the synthetic compounds. (3) Results: A two-component aggregation-sex pheromone consisting of (R)-3-hydroxyhexan-2-one and (S)-2-hydroxyoctan-3-one was identified for P. detritus. (±)-3-hydroxyhexan-2-one and (S)-2-hydroxyoctan-3-one attracted adults of P. detritus in field bioassays. Adults of the clerid C. mutillarius also were attracted to both compounds. The cerambycid Xylotrechus antilope Schönh was significantly attracted to traps baited with (S)-2-hydroxyoctan-3-one alone or the blend containing this compound. (4) Conclusions: Our data confirmed that 3-hydroxyhexan-2-one and 2-hydroxyoctan-3-one are male-produced pheromone components for P. detritus. These results show that both intraspecific and interspecific communication may play key roles in longhorn beetle life history and ecology, with closely and more distantly related species eavesdropping on each other’s signals.

Phenology of Bean Leaf Beetle (Coleoptera: Chrysomelidae) in Ontario, Canada and Field Validation of a Degree-Day Model.

The phenology and voltinism of bean leaf beetle, Cerotoma trifurcata (Forster), were examined in three counties in 2010 and two counties in 2011 in Ontario soybean, Glycine max (L.) Merr., fields. Soil samples from within cages containing field-collected beetles revealed one cycle of eggs, larvae, and pupae. Observed degree-day (DD) accumulations for C. trifurcata life stage events (egg hatch, egg hatch to pupation, and oviposition to peak adult) in field experiments were compared with thermal constants determined in a temperature-dependent development laboratory experiment where C. trifurcata were reared under five constant temperatures. Observed and predicted DDs for all life stage events were nearly identical. Mean DD accumulations from first oviposition to peak adult emergence in the field studies was 589 ± 67 DD (base 10.3°C), which was nearly identical to the model prediction (581 ± 40 DD, base 10.3°C).

Soybean Foliage Consumption Reduces Adult Western Corn Rootworm (Diabrotica virgifera virgifera)(Coleoptera: Chrysomelidae) Survival and Stimulates Flight.

Western corn rootworm, Diabrotica virgifera virgifera LeConte, biology is tied to the continuous availability of its host (corn, Zea mays L.). Annual rotation of corn with a nonhost, like soybean (Glycine max (L.) Merrill) was a reliable tactic to manage western corn rootworm. Behavioral resistance to annual crop rotation (rotation resistance) allowed some eastern U.S. Corn Belt populations to circumvent rotation by laying eggs in soybean and in cornfields. When active in soybean, rotation-resistant adults commonly consume foliage, in spite of detrimental effects on beetle survival. Rotation-resistant beetle activity in soybean is enabled by the expression of certain proteinases and an adapted gut microbiota that provide limited protection from soybean antiherbivore defenses. We investigated the effects of corn and soybean herbivory on rotation-resistant female survival and initiation of flight using mortality assays and wind tunnel flight tests. Among field-collected females tested with mortality assays, beetles from collection sites in a cornfield survived longer than those from collection sites in a soybean field. However, reduced survival due to soybean herbivory could be restored by consuming corn tissues. Field-collected beetles that fed on a soybean tissue laboratory diet or only water were more likely to fly in a wind tunnel than corn-feeding beetles. Regardless of collection site and laboratory diet, 90.5% of beetles that flew oriented their flights upwind. Diet-related changes in the probability of flight provide a proximate mechanism for interfield movement that facilitates restorative feeding and the survival of females previously engaged in soybean herbivory.

Herbivory improves the fitness of predatory beetles.

While many predatory arthropods consume non-prey foods from lower trophic levels, little is known about what drives the shift from predator to omnivore. Predatory lady beetles often consume non-prey foods like plant foliage and pollen. One species, Coccinella septempunctata, eats foliage to redress sterol deficits caused by eating sterol-deficient prey. Here we explore how omnivory benefits lady beetle fitness. We reared seven species of lady beetles-from five genera distributed across the tribe Coccinellini-on pea aphids in the presence or absence of fava bean foliage; pea aphids have very low sterol content. Foliage supplements lengthened the development times of four species and decreased survival to adulthood of two species; it had no effect on adult mass. We mated beetles in a 2×2 factorial design (males with or without foliage paired with females with or without foliage). For each species, we observed a profound paternal effect of foliage supplements on fitness. Females mated to foliage-supplemented males laid more eggs and more viable eggs compared to females mated to non-supplemented males. Foliage-supplemented males produced 2.9-4.6 times more sperm compared to non-supplemented males for the three species we examined. We analysed the sterol profile of four beetle species reared on pea aphids-with or without foliage-and compared their sterol profile to field-collected adults. For two laboratory-reared species, sterols were not detected in adult male beetles, and overall levels were generally low (total ng of sterol/beetle range: 3-33ng); the exception being Propylea quatuordecimpunctata females (total ng of sterol/beetle range: 50-157ng). Laboratory-reared lady beetle sterol content was not significantly affected by the presence of foliage. Field-collected beetles had higher levels of sterols compared to laboratory-reared beetles (2,452-145,348ng per beetle); cholesterol and sitosterol were the dominant sterols in both field-collected and laboratory-reared beetles. Our findings indicate that herbivory benefits lady beetle fitness across the Coccinellini, and that this was entirely a paternal effect. Our data provide a rare example of a nutritional constraint impacting fitness in a sex-specific manner. It also shows, more broadly, how a nutritional constraint can drive predators towards omnivory.

Modification of reproductive schedule in response to pathogen exposure in a wild insect: Support for the terminal investment hypothesis.

Trade-offs in the time and energy allocated to different functions, such as reproductive activities, can be driven by alterations in condition which reduce resources, often in response to extrinsic factors such as pathogens or parasites. When individuals are challenged by a pathogen, they may either reduce reproduction as a cost of increasing defence mechanisms or, alternatively, modify reproductive activities so as to increase fecundity thereby minimizing the fitness costs of earlier death, a behaviour consistent with the terminal investment hypothesis (TIH). The TIH predicts that individuals with decreased likelihood of future reproduction will maximize current reproductive effort, which may include shifts in reproductive timing. We examined how wild, adult female click beetles (Agriotes obscurus) responded after exposure to the fungal pathogen Metarhizium brunneum. Field-collected beetles exposed to a high concentration of M.brunneum died earlier and in greater numbers than those exposed to a low concentration. Using a multivariate approach, we examined the impact of pathogen challenge on lifespan and a suite of reproductive traits. Stepdown regression analysis showed that only female lifespan differed among the fungal treatments. Fungal-induced reductions in lifespan drove changes in the reproductive schedule, characterized by a decrease in preoviposition period. Moving the start of egg laying forward allowed the females to offset the costs of a shortened lifespan. These changes suggest that there is a threshold for terminal investment, which is dependent on strength of the survival threat. From an applied perspective, our findings imply that exposing adult click beetles to M.brunneum to reduce their population density might not succeed and is an approach that needs further investigation.

Effects of the winter temperature regime on survival, body mass loss and post-winter starvation resistance in laboratory-reared and field-collected ladybirds

Ongoing climate change results in increasing temperatures throughout the seasons. The effects of climate change on insect performance are less studied during the winter season than during the growing season. Here, we investigated the effects of various winter temperature regimes (warm, normal and cold) on the winter performance of the invasive ladybird Harmonia axyridis (Coleoptera: Coccinellidae). Winter survival, body mass loss and post-winter starvation resistance were measured for a laboratory-reared population as well as three populations collected from the field prior to overwintering. The warm winter regime increased the survival rate and body mass loss and reduced post-winter starvation resistance compared to those of the ladybirds in the cold winter regime. The effects of the temperature regime were qualitatively similar for the laboratory-reared and field-collected beetles; however, there were significant quantitative differences in all measured overwintering parameters between the laboratory-reared and field-collected populations. The winter survival of the laboratory-reared beetles was much lower than that of the field-collected beetles. The laboratory-reared beetles also lost a larger proportion of their body mass and had reduced post-winter starvation resistance. Winter survival was similar between the females and males, but compared to the males, the females lost a smaller proportion of their body mass and had better post-winter starvation resistance. The pre-overwintering body mass positively affected winter survival and post-winter starvation resistance in both the laboratory-reared and field-collected ladybirds. The significant differences between the laboratory-reared and field-collected individuals indicate that quantitative conclusions derived from studies investigating solely laboratory-reared individuals cannot be directly extrapolated to field situations.

Characterising the variables associated with Tribolium castaneum adults that initiate flight in laboratory tests – Generating predictions for the field

The flight behaviour of Tribolium castaneum was studied in the laboratory by characterising the physiological factors related to flight initiation in these small but long-lived beetles. We investigated the flight propensity of T. castaneum at two different ages at the same time: old beetles (∼12 weeks post-emergence) and young ones (∼2 weeks post-emergence). A mixture of old and young individuals was used as an independent test of whether flying beetles had the same characteristics as young beetles and residents the same ones as old. First generation laboratory cultures of field-collected beetles were used to avoid the known effects of protracted laboratory culturing. Beetles that initiated flight were captured individually in the laboratory using a customized trap, and their age, sex, weight, size, fat content, fecundity, and lipofuscin intensity (as a potential correlation of age) were determined. Beetles that had not flown in the test were simultaneously collected to represent residents (non-flyers) in each treatment. The assays indicated that flight propensity declined significantly with age (more young beetles flew than old ones), was not related to sex or weight, but was associated with size (larger beetles flew more). Lipofuscin intensity of old beetles was similar to that of young beetles, so is not a good indicator of age, but it was significantly higher in young flying females than young resident ones, so may be related to metabolic status. Fecundity assessments on a subset of the captured beetles indicate that total fecundity was not related to age or flight propensity. Based on these results we predict that most of the flying T. castaneum in the field will be relatively young beetles of high fat content. These individuals are likely to live longer than older beetles although the fecundity of females will not be higher.

Keratin decomposition by trogid beetles: evidence from a feeding experiment and stable isotope analysis

The decomposition of vertebrate carcasses is an important ecosystem function. Soft tissues of dead vertebrates are rapidly decomposed by diverse animals. However, decomposition of hard tissues such as hairs and feathers is much slower because only a few animals can digest keratin, a protein that is concentrated in hairs and feathers. Although beetles of the family Trogidae are considered keratin feeders, their ecological function has rarely been explored. Here, we investigated the keratin-decomposition function of trogid beetles in heron-breeding colonies where keratin was frequently supplied as feathers. Three trogid species were collected from the colonies and observed feeding on heron feathers under laboratory conditions. We also measured the nitrogen (δ(15)N) and carbon (δ(13)C) stable isotope ratios of two trogid species that were maintained on a constant diet (feathers from one heron individual) during 70 days under laboratory conditions. We compared the isotopic signatures of the trogids with the feathers to investigate isotopic shifts from the feathers to the consumers for δ(15)N and δ(13)C. We used mixing models (MixSIR and SIAR) to estimate the main diets of individual field-collected trogid beetles. The analysis indicated that heron feathers were more important as food for trogid beetles than were soft tissues under field conditions. Together, the feeding experiment and stable isotope analysis provided strong evidence of keratin decomposition by trogid beetles.

Supercooling in the Redbay Ambrosia Beetle (Coleoptera: Curculionidae)

The redbay ambrosia beetle, Xyleborus glabratus Eichoff, (Coleoptera: Curculionidae: Scolytinae) is a severe pest of North American trees and shrubs in the family Lauraceae. Supercooling point (SCP) is an important physiological baseline for cold tolerance studies and could provide useful insights into the invasive potential of X. glabratus in northern latitudes of North America. The supercooling point (SCP) of X. glabratus was experimentally determined on field-collected and artificially cold hardened specimens. Field-collected beetles were captured in Jackson County, Mississippi using Lindgren funnel traps baited with manuka oil lures. Testing was conducted from June through August 2011. The mean SCP for field-collected X. glabratus was -21.7 ± 0.5 °C (± SE). A significant negative trend in the SCPs of field-collected beetles occurred over the summer testing period. Xyleborus glabratus specimens were reared from redbay (Persea borbonia (L.) Sprengel bolts in June 2012 and artificially cold hardened in a low temperature incubator at a thermo-photoperiod of 7 °C:2 °C (10:14 h L:D) for 31 days. Artificially cold hardened X. glabratus supercooled to a mean temperature of -23.9 ± 0.4 °C (± SE), which was significantly lower than that of field-collected beetles. Biometric indices of beetles (size, weight, and size x weight interaction) had no effect on the mean supercooling SCPs of either field-collected or artificially cold hardened beetles. Results from environmentally conditioned beetles suggest that X. glabratus has a high degree of thermal plasticity. Based on the artificially cold hardened mean SCP, X. glabratus and laurel wilt disease have the possibility to impact sassafras and northern spicebush throughout eastern North America. The data, although preliminary, suggests that a previous spatio-temporal model based on climate match data may have substantially underestimated the geographical area that may be affected by X. glabratus. This study will help form the basis of building and validating models to better predict the North American invasion potential of X. glabratus.

Association of the pine-infesting Pissodes species with ophiostomatoid fungi in Poland

Bark weevils are consistently associated with various fungi. They act as effective vectors for root-rot fungi, the rust pathogen and the ophiostomatoid fungi. In comparison with bark beetles, the interaction between ophiostomatoid fungi and bark weevils has been poorly studied in Europe. This study aims to clarify the ties among ophiostomatoid fungi and their weevil vectors in Pinus sylvestris. Samples associated with three bark weevils, including Pissodes castaneus, P. piniphilus and P. pini were collected from seven pine stands in Poland. Fungi were isolated from laboratory-reared and field-collected beetles, larvae and galleries of weevils. Isolates were identified based on morphology, DNA sequence comparison for two gene regions (ITS, s-tubulin) and phylogenetic analyses. Fourteen morphological and phylogenetic ophiostomatoid species were identified among the 1,219 isolates. These 14 species included 11 novel associations between fungi and bark weevils. The most commonly encountered fungal associates of bark Pissodes species were Leptographium procerum, Ophiostoma quercus and O. minus. The spectrum of fungal associates was similar in three bark weevil species, despite some differences between species. Except for P. castaneus, all species of bark weevil were frequently associated with ophiostomatoid fungi. Pissodes castaneus does appear to be a consistent vector of L. procerum and Sporothrix inflata while O. minus, O. quercus and O. cf. rectangulosporium were often found in association with P. piniphilus and P. pini.

Stable isotopes and elements as biological markers to determine food resource use pattern by Lasioderma serricorne (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae) is a pest of durable grain commodities, spices, and stored tobacco. Larvae cause most feeding damage to commodities; adult L. serricorne rarely feed and are good fliers. Since L. serricorne can potentially disperse between different landscapes and may feed on different hosts, understanding insects' host use pattern may help to direct management efforts to specific commodity storages. In this study, quantitative and qualitative differences of carbon and nitrogen isotopes and five inorganic elements (Mg, Mn, Fe, Cu and Zn) present in the insect body tissue were used to identify the dietary history of L. serricorne. Adults reared on different hosts in the laboratory, including respective rearing media and insects collected from different field locations, were used in the study. The δ13C values in the laboratory, reared L. serricorne, were similar to the values of respective rearing media with an enrichment of about 1‰ in the insect body. The enrichment for δ15N value greatly increased from host to insect body and varied about +3.30 to +5.73‰ in beetles. There was a distinct difference in δ13C values for insects raised on C3-based or C4-based hosts. A majority of the field-collected beetles showed δ13C values similar to expectations for a C3 plant (−20 to −28‰); however, a few beetles showed evidence for feeding on C4 plants (<−14‰) or diet mixing between C3 and C4 plants. Of the five inorganic elements evaluated, only Mn showed distinct variation in concentrations between the rearing media and insect body. This study shows potential exists for delineating the food sources of L. serricorne, using carbon and nitrogen stable isotopes and elements like Mn.

Use of macro and trace elements as biological markers in the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The relationship between the occurrence and movements of Rhyzopertha dominica (F.), a serious pest of stored cereal grains, in distinctly different habitats is poorly known. Understanding the feeding ecology and dispersal patterns of R. dominica may likely help predict the abundance or movement of this pest in various habitats. Natal sites and movement of insects are studied using intrinsic methods involving elemental analyses. In this study, to understand the dietary history of R. dominica, trace and macro elements were used as potential markers. Insects reared on selected diets under laboratory conditions and adult beetles collected from the periphery of granaries or inside forested woodlands were used to determine 10 different elements in their body tissues. Quantities of 10 elements were also determined in respective laboratory hosts. The main discriminant elements for laboratory-reared R. dominica were Na, S and Zn, while significantly different elements were distinctive among field-collected beetles and included P, Ca, K, Zn, and Cu. The amount of Zn quantified in acorn-fed lab reared beetles was significantly lower than wheat- or corn-fed insects. Similarly, beetles captured in woodlands had significantly lower Zn in their body signatures, suggesting acorn seeds may have served as an alternate host in Quercus spp. dominated woodlands. Our studies showed that elemental profiles may potentially be used as biological markers for delineating food sources of R. dominica to mainly discriminate whether beetles originated in agricultural vs. wooded habitats.

A Male-Produced Aggregation Pheromone of Monochamus alternatus (Coleoptera: Cerambycidae), a Major Vector of Pine Wood Nematode

The beetle Monochamus alternatus Hope (Coleoptera: Cerambycidae) is an efficient vector of pine wood nematode, the causal pathogen of pine wilt disease, that has resulted in devastating losses of pines in much of Asia. We assessed the response of adult M. alternatus to 2-(undecyloxy)-ethanol, the male-produced pheromone of the congeneric M. galloprovincialis Dejean, in field experiments in Fujian Province, People's Republic of China. Both sexes of M. alternatus were attracted to lures consisting of 2-(undecyloxy)-ethanol combined with the host plant volatiles alpha-pinene and ethanol. A follow-up experiment showed that 2-(undecyloxy)-ethanol was synergized by both ethanol and alpha-pinene. Coupled gas-chromatography mass-spectrometry analyses of volatiles sampled from field-collected beetles of both sexes revealed that 2-(undecyloxy)-ethanol was a sex-specific pheromone component produced only by males. The combination of 2- (undecyloxy) -ethanol with ethanol and/or alpha-pinene will provide a valuable and badly needed tool for quarantine detection, monitoring, and management of M. alternatus.

Bacterial Communities Associated with the Digestive Tract of the Predatory Ground Beetle, Poecilus chalcites, and Their Modification by Laboratory Rearing and Antibiotic Treatment

Ground beetles such as Poecilus chalcites (Coleoptera: Carabidae) are beneficial insects in agricultural systems where they contribute to the control of insect and weed pests. We assessed the complexity of bacterial communities occurring in the digestive tracts of field-collected P. chalcites using terminal restriction fragment length polymorphism analyses of polymerase chain reaction-amplified 16S rRNA genes. Bacterial identification was performed by the construction of 16S rRNA gene clone libraries and sequence analysis. Intestinal bacteria in field-collected beetles were then compared to those from groups of beetles that were reared in the lab on an artificial diet with and without antibiotics. Direct cell counts estimated 1.5x10(8) bacteria per milliliter of gut. The digestive tract of field-collected P. chalcites produced an average of 4.8 terminal restriction fragments (tRF) for each beetle. The most abundant clones were affiliated with the genus Lactobacillus, followed by the taxa Enterobacteriaceae, Clostridia, and Bacteriodetes. The majority of the sequences recovered were closely related to those reported from other insect gastrointestinal tracts. Lab-reared beetles produced fewer tRF, an average of 3.1 per beetle, and a reduced number of taxa with a higher number of clones from the family Enterobacteriaceae compared to the field-collected beetles. Antibiotic treatment significantly (p<0.05) reduced the number of tRF per beetle and selected for a less diverse set of bacterial taxa. We conclude that the digestive tract of P. chalcites is colonized by a simple community of bacteria that possess autochthonous characteristics. Laboratory-reared beetles harbored the most common bacteria found in field-collected beetles, and these bacterial communities may be manipulated in the laboratory with the addition of antibiotics to the diet to allow study of functional roles.

Overwintering and Seasonal Patterns of Feeding and Reproduction inPhyllotreta cruciferae(Coleoptera: Chrysomelidae) in the Northeastern United States

The life history of the agricultural pest Phyllotreta cruciferae (Goeze), including location of overwintering sites, time of spring emergence, reproductive phenology, and seasonal changes in feeding and responsiveness to yellow sticky traps, was studied in the northeastern United States from 2001 to 2003 to provide growers with information to improve their management of flea beetle populations in Brassica crops. Samples of leaf litter, organic debris, and soil were collected from a variety of vegetation types to determine the location of flea beetle overwintering sites surrounding agricultural fields. Significantly more P. cruciferae were found in the leaf litter beneath shrubs and brush or in wooded areas than in grass, within-field debris, or in soil samples taken within each vegetation type. Weekly dissections of field-collected female beetles suggested the occurrence of a partial second generation by P. cruciferae in 2003. In laboratory assays of beetles collected weekly from Brassica fields in Massachusetts, both adult beetle feeding on Brassica foliage and beetle responsiveness to yellow sticky traps shows two peaks (June and August) that corresponded to the first and second generations. Beetle catch on yellow sticky traps was highly correlated (2002: R2 = 0.8; 2003: R2 = 0.6) with the mean number of feeding holes on injured plants.

Rearing Protocol and Life History Traits for Poecilus chalcites (Coleoptera: Carabidae) in the Laboratory

A rearing protocol for the predaceous ground beetle, Poecilus chalcites (Say), is described. The effects of dietary constituents, substrate moisture content, and substrate type on larval developmental rates and size were examined in the laboratory. The protocol was successful in obtaining nearly 80% pupation rates, although adult size was smaller than field-collected beetles, and laboratory-produced adults did not lay eggs. We determined experimentally that some of the components of the meridic diet used for colony production could be removed without compromising larval size or developmental rates, but that nutrition beyond cat food was necessary to increase larval size. We found a positive correlation of larval size with increased moisture content using vermiculite substrate at three moisture levels (33.3, 50.0 and 66.7% by weight). Untreated Fer-Til® (GreenGro Products, Jackson, WI) soil resulted in the highest pupation rate (70 to 80%) and had one of the shortest developmental periods of the five soils tested. Steaming or sifting Fer-Til soil compromised its ability to support larval development until pupation.

Multivariate Analysis of Morphological Variation in Two Cryptic Species of &lt;I&gt;Sancassania&lt;/I&gt; (Acari: Acaridae) from Costa Rica

Populations of Sancassania mites were collected in Costa Rica from scarabaeid and passalid beetles and cultured. The populations proved to be reproductively incompatible due to postzygotic isolation and show 1.4% difference in domains 2 and 3 of the 28S nuclear rDNA gene, indicating the populations represent distinct species. Because the mites were virtually indistinguishable morphologically, 61 morphological characters of 50 females and 101 characters of 60 deutonymphs of the two species were analyzed. Traditional univariate morphometrics could not separate them. Multivariate analyses of variance (principal component and discriminant function) were used to interpret morphological differences between the two species in relation to factors that influence their morphology in a laboratory and field setting. Principal component analyses were done on size and shape as well as shape variables alone. The discriminant function analysis was done on a reduced subset of shape variables. In both cases, the shape analyses resulted in complete separation of the two species and the characters contributing strongly to the discrimination were used in formal description of the two species, Sancassania salasi sp. nov. and S. ochoai sp. nov. Although deutonymphs of S. salasi taken from field-collected beetles show a significantly smaller magnitude of size variation, they show significant deviation in shape compared with cultured deutonymphs of the same species, a potential problem for correlation of specimens of other Sancassania species from culture and nature. Characters that provide the strongest contribution to these intraspecific shape changes are, therefore, taxonomically unreliable.

Distribution, host range, and climatic constraints on Centistes gasseni (Hymenoptera: Braconidae), a South American parasitoid of cucumber beetles, Diabrotica spp. (Coleoptera: Chrysomelidae).

The genus Diabrotica includes a large number of pest species, including some of the most important crop pests of the Americas. The parasitoid Centistes gasseni Shaw is the first braconid to be described parasitizing Diabrotica in South America, and high natural infestations are reported. Field and experimental observations on the host range, distribution and biology of this parasitoid are described. Centistes gasseniwas collected in southern Brazil, eastern Paraguay and northeastern Argentina, in a region comprising humid lowlands and highlands, and cool temperate to warm subtropical climates, with regular rainfall in excess of 1300 mm. Three Diabroticaspecies, D. limitata (Sahlberg), D. speciosa (Germar) and D. viridula (Fabricius) were found to host the parasitoid, with mean percent parasitism of 5.4, 2.0 and 1.0%, respectively. Diabrotica speciosa and D. viridula are the two most important pest Diabroticaspecies in South America. Laboratory experiments with field-collected beetles and parasitoid cocoons indicated that C. gasseni overwinters in adult host beetles, remaining dormant in its live host below developmental temperatures. A potential distribution of C. gasseni in North America is proposed based on its known climatic range and the distribution of the main pest species of adult overwintering North American Diabrotica.

Oviposition, Development, and Feeding of &lt;I&gt;Scymnus&lt;/I&gt; (&lt;I&gt;Neopullus&lt;/I&gt;) &lt;I&gt;sinuanodulus&lt;/I&gt; (Coleoptera: Coccinellidae): A Predator of &lt;I&gt;Adelges tsugae&lt;/I&gt; (Homoptera: Adelgidae)

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.