Late Instar Nymphs Research Articles

Description of a new Ornithodoros (Pavlovskyella) (Ixodida: Argasidae) tick species from Pakistan.

The genus Ornithodoros is notably diverse within the family Argasidae, comprising approximately 134 species distributed among 4 subgenera, 1 of which is the subgenus Pavlovskyella. In an earlier study, we identified distinct soft ticks as Ornithodoros (Pavlovskyella) sp., which were collected from animal shelters in Khyber Pakhtunkhwa, Pakistan. Providing additional collections from that same locality and a comprehensive analysis involving detailed morphological and mitogenome-based comparisons with closely related species, this study formally designates a novel species for these specimens. Adults and late-instar nymphs of the new species display a dorsoventral groove, small cheeks not covering the capitulum, 5 small even humps on tarsus I and a transverse postanal groove intersecting the median postanal groove perpendicularly. It also lacks a tuft of setae on the ventral surface of the hood which separates the novel species from Ornithodoros papillipes. Ventral chaetotaxy of tarsus IV indicates 4–7 setal pairs in nymphs and 5–7 pairs in adults that separate the new species from Ornithodoros tholozani sensu stricto and Ornithodoros crossi, 2 morphologically closely related species that occur in geographical proximity. Phylogenetic analyses of the full-length mitochondrial genome and the 18S and 28S ribosomal RNA genes, combined with pairwise nucleotide comparisons of cox1, cox2, atp8, atp6, cox3, nad3, nad5, nad4, nad4L, nad6, cytb, nad1, nad2, 12S rDNA, 16S rDNA, 18S rDNA and 28S rDNA further support that the new species belongs to the Pavlovskyella subgenus, clustering with O. tholozani, Ornithodoros verrucosus and Ornithodoros tartakovskyi.

Endosymbiont and gut bacterial communities of the brown-banded cockroach, Supella longipalpa.

The brown-banded cockroach (Supella longipalpa) is a widespread nuisance and public health pest. Like the German cockroach (Blattella germanica), this species is adapted to the indoor biome and completes the entirety of its life cycle in human-built structures. Recently, understanding the contributions of commensal and symbiotic microbes to the biology of cockroach pests, as well as the applications of targeting these microbes for pest control, have garnered significant scientific interest. However, relative to B. germanica, the biology of S. longipalpa, including its microbial associations, is understudied. Therefore, the goal of the present study was to quantitatively examine and characterize both the endosymbiont and gut bacterial communities of S. longipalpa for the first time. To do so, bacterial 16S rRNA gene amplicon sequencing was conducted on DNA extracts from whole adult females and males, early instar nymphs, and late instar nymphs. The results demonstrate that the gut microbiome is dominated by two genera of bacteria known to have beneficial probiotic effects in other organisms, namely Lactobacillus and Akkermansia. Furthermore, our data show a significant effect of nymphal development on diversity and variation in the gut microbiome. Lastly, we reveal significant negative correlations between the two intracellular endosymbionts, Blattabacterium and Wolbachia, as well as between Blattabacterium and the gut microbiome, suggesting that Blattabacterium endosymbionts could directly or indirectly influence the composition of other bacterial populations. These findings have implications for understanding the adaptation of S. longipalpa to the indoor biome, its divergence from other indoor cockroach pest species such as B. germanica, the development of novel control approaches that target the microbiome, and fundamental insect-microbe interactions more broadly.

Assessing acceptability of wild and cultivated hosts of Lycorma delicatula (Hemiptera: Fulgoridae) under semifield conditions.

Lycorma delicatula White (Hemiptera: Fulgoridae) is an invasive phloem feeder with a broad host range that includes both hardwood trees and cultivated temperate fruit crops. Here, we evaluated acceptability of wild hosts, A. altissima and Juglans nigra L. (Fagales: Juglandaceae) and cultivated hosts Vitis vinifera, Malus domestica (Rosales: Rosaceae), and Prunus persica L. Batsch (Rosales: Rosaceae) to L. delicatula under field conditions. Fluorescent-marked early instar nymphs, late instar nymphs, or adult L. delicatula were released at the base of single potted host plants and the number of individuals retained was recorded over 24 h. Paired choice trials with A. altissima and another host plant were conducted. Individuals retained on or moving between plants were recorded over 24 h. Sentinel A. altissima, J. nigra, V. vinifera, M. domestica, and P. persica potted plants were deployed at 5 sites and the number of L. delicatula present on each plant was recorded weekly. In single and paired host trials, early instars and adults were generally retained in higher numbers on A. altissima and V. vinifera, and late instars were retained on A. altissima and J. nigra. Significantly more L. delicatula were present on sentinel A. altissima compared with other host plants, except J. nigra during the period when late instars were the most prevalent lifestage in the field. These results indicate that wild hosts such as A. altissima and J. nigra are likely supporting establishment of L. delicatula populations, and that presence of cultivated V. vinifera may contribute to population establishment and growth.

Survival and development of Lycorma delicatula (Hemiptera: Fulgoridae) on common secondary host plants differ by life stage under controlled conditions.

Host range assessment for emerging invasive insects is a vital step toward fully defining the issues the insect may pose. Spotted lanternfly (SLF) is an invasive species that is rapidly expanding its presence in the United States. The primary hosts facilitating this spread are tree of heaven, a plant from SLF's native range, and the economically important winegrape. Black walnut is also implicated as an important and common host plant. This study investigated the survival and development of SLF on diets that included a variety of crop host plants in the presence or absence of tree of heaven. The following plant species, 'Honeycrisp' apple, 'Reliance' peach, silver maple, and tree of heaven were paired with winegrape or black walnut throughout the study. SLF had strong development and high survival on a diet of winegrape alone, and winegrape or black walnut paired with tree of heaven. Survival parameters were reduced with all other plant pairings. In particular, SLF in the winegrape and peach diet treatment did not develop past the third nymphal instar. A second experiment evaluated the survival of early and late instar nymphs and adult SLF life stages on three specialty crops - 'Cascade' hops, muscadine grapes, and kiwifruit over a two-week period. Nymphs survived longer than adults, with survival of first and second instar nymphs on hops not differing from the control tree of heaven treatment. The adult stage survived best on kiwi and muscadine grape. Our results show tree of heaven and winegrape were the only single plant diets evaluated that are sufficient for complete SLF development, while other host plants may require additional host or hosts of sufficient nutritional quality for SLF survival.

Identification and Validation of Reference Genes for Expression Analysis Using qRT-PCR in Cimex hemipterus (Hemiptera: Cimicidae).

The tropical bed bug, Cimex hemipterus (F.) (Hemiptera: Cimicidae) is an important public-health pest that feeds on the blood of humans and some other animals. To explore the function of the target genes of C. hemipterus, it is essential to select suitable reference genes for the accurate quantification of gene expression. Here, we selected 10 frequently used reference genes in insects and evaluated their stability in C. hemipterus under various biotic (developmental stage, sex, and tissue) and abiotic (gas stimulation and temperature) conditions through RefFinder (which integrates four computational programs: geNorm, NormFinder, BestKeeper, and ∆Ct). Results indicate that the optimal combination of reference genes for each experimental condition was as follows: RPL8 and EF1α for the developmental stage (eggs, early instar nymphs, late instar nymphs, and adults), RPL8 and RPS16 for adult sex, RPL8 and RPL11 for adult tissue (head, thorax, abdomen, and legs), RPL8 and β-tubulin for gas stimulation (air and carbon dioxide), and RPL8 and NADH for temperature (0, 5, 17, 30, and 37 °C). Finally, the expression pattern of the HSP70 and GR21 genes were analyzed, and the results highlight the importance of appropriate reference-gene selection. Our results provide a comprehensive list of optimal reference genes from C. hemipterus for the first time, which will contribute to accurately analyzing the expression of target genes.

Cold Tolerance of Mountain Stoneflies (Plecoptera: Nemouridae) from the High Rocky Mountains

How aquatic insects cope with cold temperatures is poorly understood. This is particularly true for high-elevation species, which often experience a seasonal risk of freezing. In the Rocky Mountains, nemourid stoneflies (Plecoptera: Nemouridae) are a major component of mountain stream biodiversity and are typically found in streams fed by glaciers and snowfields, which are rapidly receding due to climate change. Predicting the effects of climate change on mountain stoneflies is difficult because their thermal physiology is largely unknown. We investigated cold tolerance of several alpine stoneflies (Lednia tumana, Lednia tetonica, and Zapada spp.) from the Rocky Mountains, USA. We measured the supercooling point (SCP) and tolerance to ice enclosure of late-instar nymphs collected from a range of thermal regimes. SCPs varied among species and populations, with the lowest SCP measured for nymphs from an alpine pond, which was much more likely to freeze solid in winter than flowing streams. We also show that L. tumana cannot survive being enclosed in ice, even for short periods of time (<3 h) at relatively mild temperatures (–0.5 °C). Our results indicate that high-elevation stoneflies at greater risk of freezing may have correspondingly lower SCPs, and despite their common association with glacial meltwater, these stoneflies appear to be living near their lower thermal limits.

Eucalypt susceptibility towards the invasive Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae) in South Africa

Glycaspis brimblecombei (Hemiptera: Aphalaridae) is a eucalypt feeder native to Australia. Infestations of G. brimblecombei can cause leaf wilt, dieback and death in weak or severely infested plants. In many countries where G. brimblecombei has been introduced, patterns of susceptibility of different Eucalyptus hosts have been observed or tested. However, these host susceptibilities are not always comparable between countries due to the different composition of species planted, and the possible influence of the different environments on host susceptibility. We investigated the patterns of host susceptibility of 28 commercial eucalypt varieties in South Africa by comparing the number of early and late instar nymphs, using both choice and no choice tests. We also examined the possible influence of leaf colour on susceptibility, following a previous report that G. brimblecombei preferred red to other colours. Our study confirmed the susceptibility of specific varieties towards G. brimblecombei, in particular Eucalyptus grandis W.Hill × Eucalyptus camaldulensis Dehnh. One of the least and one of the most susceptible eucalypts had almost identical wavelengths, indicating that leaf colour, with particular reference to red, is unlikely to play a role in host plant selection.

Feeding Behavior of Nezara viridula First Instars: EPG Analysis and Effect of Food Availability on Subsequent Development

Assertions that first-instar pentatomids “do not feed” are pervasive in the literature. Recent research using rifampicin-resistant marked bacteria demonstrated that first-instar southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), ingest from green bean. The technique of electropenetrography (EPG), coupled with histology, has allowed researchers to elucidate feeding behavior within plant tissue, and recordings of several species (including N. viridula) have shown that internal stylet probes of adults and late-instar nymphs may terminate in xylem as well as in seed endosperm, inner pod wall, or stem parenchyma. The seeming contradiction regarding “feeding” could be explained if first instars were simply hydrating from plant tissue to maintain water balance. In this study, first-instar N. viridula were supplied with either water or green bean, and subsequently given a traditional rearing diet (green bean and peanut) from second instar onward. We noted aggregations of first instars forming on water wicks and on beans along the carpellary bundles and at both tips. Availability of food (green bean) in first instar did not affect subsequent development. Using EPG, we recorded first-instar N. viridula probing on soybean leaves and found the primary waveform to be xylem ingestion. Probing and ingestion behavior did not differ between first instars previously exposed to high and moderate humidity conditions. We conclude that these insects ingest from xylem, but nutrients other than water are not required in the first instar for successful nymphal development.

Efficacy of insecticides against invasive rugose spiralling whitefly Aleurodicus rugioperculatus martin on Banana

Laboratory and field evaluation of some insecticides (buprofezin 25 SC, pymetrozine 50 WG, flonicamid 50 WG, dinotefuran 20 SG, thiamethoxam 25 WG, profenophos 50 EC), botanical (azadirachtin 10000 ppm) and entomopathogenic fungus (Isaria fumosorosea Wize) were carried out against the invasive rugose spiralling whitefly Aleurodicus rugioperculatus Martin on banana. The results revealed that azadirachtin 10000 ppm (86.49%), dinotefuran 20 SG (82.64%), pymetrozine 50 WG (72.72%) and thiamethoxam 25 WG (79.59%) caused significant mortality of first and second instar nymphs at 2 days after treatment (DAT). Profenophos 50 EC (77.61%) and azadirachtin 10000 ppm (71.53%) were significantly effective and on par with mortality at 2 DAT of third and fourth instar nymphs. Flonicamid 50 WG was the most toxic with the least LC50 value (507.8 and 646.1) and buprofezin 25 SC was the least toxic with maximum value (1245.1 and 1752.0) for early and late instar nymphs, respectively. Profenophos 50 EC and LC50 buprofezin 25 SC also showed maximum ovicidal effect. Under field conditions, I. fumosorosea with 100% mortality was significantly superior compared to dinotefuran 20 SG (97.23%), thiamethoxam 25 WG (95.02%) and azadirachtin 10000 ppm (94.98%) at 6 DAT.

First evidence of protein-carbohydrate regulation in a plant bug (Lygus hesperus)

Lygus bugs are highly polyphagous piercing/sucking insects found throughout North America. Collectively, they have been reported to feed on over 330 plant species (one of the broadest host range ever documented for a group of insects); they also feed on many economically important crops. Despite its prevalence across North America and status as a common pest in many agroecosystems, very little is known about how Lygus bugs regulate their intake of nutrients. In reality, little is known about nutrient regulation for most hemipterans, specifically non-phloem feeding species in the suborder Heteroptera. This likely reflects difficulties in developing adequate artificial diets for insects with piercing/sucking mouthparts. There is, however, an artificial diet for L. hersperus, and in this study we modified it and performed choice and no-choice experiments to determine how L. hesperus regulates its intake of two macronutrients – protein (p) and carbohydrates (c) – that are tightly linked to survival and performance in other insect herbivores. In choice experiments L. hesperus was allowed to select between two foods with different protein:carbohydrate ratios. We documented strong regulation for protein and carbohydrates, with late instar nymphs selecting a slightly protein-biased intake target (protein-carbohydrate ratio = 1.5:1). We also performed no-choice experiments, where nymphs were restricted to a single food. Here, the protein-carbohydrate ratio of their food had a strong impact on survival, which was highest for nymphs reared on the treatment with a protein-carbohydrate ratio closest to the self-selected intake target (determined by the choice experiments), but no significant impact on developmental time or mass gain. Our data are the first of their kind for a non-phloem feeding hemipteran and provide a starting point for more broadly understanding and further investigating the nutritional ecology/physiology of Lygus bugs. Our study also provides a framework for exploring nutrient regulation in other hemipterans and for optimizing artificial diets for piercing/sucking insects, especially heteropterans.

Influence of starvation on walking behavior of Bagrada hilaris (Hemiptera: Pentatomidae).

Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) is an invasive stink bug species that feeds on cruciferous plants and can cause substantial damage to crops. Little is known about the dispersal behavior of B. hilaris, but movement is important because of the way this pest moves from senescing weed hosts into crop fields. Perhaps, B. hilaris residing on declining weed hosts become starved, which alters their normal locomotor activity and initiates dispersal. We examined the influence of starvation on the locomotor behavior of multiple life stages of B. hilaris under laboratory and outdoor conditions. We starved nymph (2nd/3rd and 4th/5th instars) and adult (female and male) stages for 0, 24, and 48 h. We measured distance moved in the laboratory and then distance moved and turning ratio outdoors. In the laboratory, the younger nymphs moved shortest distances when starved for 24 h, whereas late-instar nymphs (4th-5th instars) and adult B. hilaris that were starved moved farther than non-starved individuals. In the outdoor setting, environmental conditions, specifically surface temperature were important in determining how starvation affected distance moved. Starved insects were more responsive (moved farther) for a given change in temperature than non-starved insects. At lower temperatures, B. hilaris tended to move farther when non-starved and at higher temperatures, moved longer distances when starved, at least for certain stages. Increased starvation also led to more directional movement. Our results indicate that starvation influences aspects of movement for B. hilaris and that these effects can be influenced by temperature.

A comprehensive omics analysis and functional survey of cuticular proteins in the brown planthopper

Cuticle, mainly composed of chitin and cuticular proteins (CPs), is a multifunctional structure of arthropods. CPs usually account for >1% of the total insect proteins. Why does an insect encode so many different CP genes in the genome? In this study, we use comprehensive large-scale technologies to study the full complement of CPs (i.e., the CP-ome) of the brown planthopper (BPH), Nilaparvata lugens, a major rice plant pest. Eight CP families (CPR, CPF, TWDL, CPLCP, CPG, CPAP1, CPAP3, and CPAPn) including 140 proteins in BPH, in which CPAPn is a CP family that we discovered. The CPG family that was considered to be restricted to the Lepidoptera has also been identified in BPH. As reported here, CPLCP family members are characterized by three conserved sequence motifs. In addition, we identified a testis protein family with a peritrophin A domain that we named TPAP. We authenticated the real existence of 106 proteins among the 140 CPs. RNA interference (RNAi) experiments were conducted against 135 CP genes in early- and late-instar nymphs and newly emerged female adults, demonstrating that 32 CPs were essential for BPH normal development or egg production. Combined RNAi experiments suggested redundant and complementary functions of the large number of CPs. Transcriptomic data revealed that the CP genes were expressed in a tissue-specific manner, and there were four clusters of developmental expression patterns. This study gives a comprehensive understanding of the roles of CPs in an insect cuticle.

Astata unicolor (Hymenoptera: Crabronidae) Population in Oregon With Observation of Predatory Behavior on Pentatomidae

Predatory wasps are one of the few natural enemies to attack late instar pentatomid nymphs and adults. However, there is a substantial lack of information about their flight and nesting behavior, making them poorly understood. We report 3 yr of observational data of Astata unicolor Say 1824 foraging behavior and phenology from a residential site in Portland, OR. A. unicolor attacked and paralyzed at least four hemipteran species, and 64% of paralyzed prey were from the invasive Halyomorpha halys (Stal; Hemiptera: Pentatomidae). Peak flight occurred between late July and mid-September. Though unmanaged and solitary, A. unicolor’s preference for H. halys demonstrates that native predators contribute to mortality and potentially management of economically important insects. This is one of the few studies to document predatory wasps’ potential for biological control of H. halys. Additional work on Astata is necessary to determine whether trap nesting, dispersal, or habitat enhancement, broadens the potential for expanded biological control.

Yellow, red, dead: the nutritional consequences for Cardiaspina densitexta (Hemiptera: Aphalaridae) nymphs of inducing senescence in old Eucalyptus fasciculosa leaves

AbstractMany psyllids are manipulative herbivores that alter their hosts to provide shelter and ameliorate nutritional quality. Among eucalypt‐feeding psyllids, Cardiaspina have specialised to manipulate natural processes of foliar senescence and thereby host nutritional quality but not foliar morphology. Using a natural outbreak, we assessed the effects of feeding by nymphs of Cardiaspina densitexta Taylor, ultraviolet exposure and temperature on changes in nutritional quality and leaf abscission. Over 6 months, we followed the responses of tagged Eucalyptus fasciculosa F.Muell. leaves that, at the beginning of the study, were at one of three different stages of utilisation by psyllids (no psyllids, only eggs present, or leaves with late instar nymphs and red lesions). We measured foliar pigments, free amino acids and polyphenols every second month to characterise foliar nutritional quality. Psyllid feeding was briefly associated with chlorosis but lesions rapidly turned red (anthocyanic) and died after nymphs had matured. Red leaves had shortened longevities and their risk of abscission was positively correlated with the UV‐index rating of the preceding fortnight but not with psyllid abundance or area necrotic. Hence, psyllids altered the balance of chlorophylls and anthocyanin‐equivalents of green leaves and presumably therefore their ability to fully utilise incoming light energy. Green leaves had distinct free amino acids and polyphenol compositions compared to red leaves. In green leaves, changes in anthocyanin‐equivalents were negatively correlated with methionine while in red leaves psyllids were positively correlated with threonine and negatively correlated with leucine. Feeding by Cardiaspina densitexta nymphs is associated with the visible symptoms of photodamage which are associated with pronounced changes in nutritional quality. These changes are not analogous to foliar hypersensitive responses because they are expressed by old leaves, necrotic tissues are not abscised, they occur late in the development of nymphs and do not directly affect their survival. Specialisation of Cardiaspina on old eucalypt leaves may appear maladaptive if these modules are considered to be low in amino nitrogen and high in polyphenols. This perspective needs refining given the influence of photodamage on nutrient availability and because condensed tannins (weak pro‐oxidants) are more abundant than hydrolysable tannins in old leaves.

Environmental and hormonal control of body color polyphenism in late-instar desert locust nymphs: Role of the yellow protein

Locusts show body color polyphenism that is considered to be an adaptation to various biotic and abiotic environmental changes. In Schistocerca gregaria, wild-type late-instar nymphs growing under crowded conditions (gregarious form) develop yellow and black body coloration, whereas they assume various body colors under isolated conditions (solitarious form). Black and green body colorations are induced by the neuropeptide corazonin (Crz) and juvenile hormone (JH), respectively. To characterize the molecular mechanisms controlling body color polyphenism, we investigated factors influencing body coloration in S. gregaria. We report here that yellow body coloration in the last nymphal instar is caused by the yellow protein of the takeout family (YPT) in this locust. YPT transcription was enhanced under high-temperature conditions during which the nymphs turned bright yellow and had little black patterning. RNAi-mediated YPT knockdown suppressed the appearance of yellow individuals and yellow staining in the exuviae. In albino nymphs, injection of JH induced yellow and green coloration and enhanced the YPT expression levels in both yellow and green individuals. YPT knockdown also suppressed yellow staining in the exuviae but did not prevent the appearance of yellow individuals. Therefore, another factor or pigment may contribute to the observed yellow body color. Injection of Crz into wild-type nymphs caused darkening and suppressed yellowing and YPT expression at high temperatures. Thus, Crz signaling could inhibit yellowing by suppressing YPT expression. Rearing cup substrate color significantly influenced YPT expression in albino nymphs both under isolated and crowded conditions. In contrast, substrate color affected YPT expression in wild-type nymphs only under isolated conditions. From these results, we conclude that YPT is an important factor in the control of body color polyphenism in S. gregaria, and its expression is influenced by temperature, JH, Crz, and substrate color of the growing environment.

Laboratory Evaluations of the Foraging Success ofTamarixia radiata(Hymenoptera: Eulophidae) on Flowers and Extrafloral Nectaries: Potential use of Nectar Plants for Conservation Biological Control of Asian Citrus Psyllid (Hemiptera: Liviidae)

Tamarixia radiata (Waterson) (Hymenoptera: Eulophidae) is a specialist parasitoid of late-instar nymphs of Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Liviidae), a vector of the causal agent of huanglongbing disease of citrus (Sapindales: Rutaceae). Tamarixia radiata is mass reared; however, parasitism levels following inundative releases have remained relatively low. One possible explanation for the low parasitism levels is the lack of sugar resources available for adult wasps in targeted release landscapes, such as abandoned commercial citrus groves and residential areas. Establishing nectar plants can be an effective means of increasing nutritional resources in targeted sites for biocontrol agents. Some eulophids forage effectively only on fully exposed nectaries, i.e., those unobstructed by other floral parts. Therefore, care must be taken to select plants that possess nectary architecture compatible with parasitoid morphology and foraging ability. A series of laboratory studies were undertaken as a first step to determine the potential for T. radiata to obtain sugar from natural sources in target landscapes. Following contact with a sugar spot on filter paper, the wasps engaged in stereotypical zigzagging movements, demonstrating that contact with sugar induced arrestment and induction of localized searching behavior. Tamarixia radiata fed on sugars found in nectar (sucrose, glucose, fructose) and honeydew (melizitose, raffinose), indicating that it should feed well on both nectar and honeydew resources. At the highest concentration tested (1 M), it preferred sucrose and melizitose, whereas at the lowest concentration tested (0.1 M), it preferred sucrose and glucose. There was no preference among sugars when tested at the 0.5 M concentration. Choice tests with wasps previously exposed to scented sucrose solution showed that the wasps were stimulated and attracted by nectar odor and could learn to associate a particular odor with the presence of nectar. Observations conducted with starved wasps on freshly cut sprigs of nectar plants showed that foraging success was highest on extrafloral nectaries and flowers with exposed nectaries. The wasps readily located the extrafloral nectaries on snap bean and cowpea, and fed on them for the majority of the observation periods. Likewise, they quickly located the fully exposed nectaries in the inflorescences of euphorbiaceous plants, such as Euphorbia heterophylla L. (Malpighiales: Euphorbiaceae). Foraging success declined in flowers with nectaries that were only partially exposed; the wasps' movements were deterred by floral parts or trichomes that obstructed the nectary. The wasps were unable to obtain nectar from composites and other plants with hidden nectaries. Overall, the results of these laboratory evaluations showed that T. radiata responds to sugars and chemical cues associated with nectaries and is capable of foraging on extrafloral nectaries and flowers with exposed nectaries.

Key to Plecoptera nymphs from the Brazilian Amazon (Insecta).

Nymphs of 22 species of Plecoptera from the Brazilian Amazon are keyed and illustrated to enhance their usefulness as water quality indicator taxa. Four described species of Anacroneuria, two species of Macrogynoplax, and two species of Enderleina have been associated with adults: Anacroneuria marlieri, A. manauensis, A. minuta, A. singularis, M. delicata, M. pulchra, E. froehlichi, and E. flinti. Nymphs of 14 additional morphospecies not yet associated with adults are included. Characters of the head, pronotum, mesonotum, and metanotum are used to distinguish late instar nymphs.

Body‐color and behavioral responses by the mid‐instar nymphs of the desert locust, Schistocerca gregaria (Orthoptera: Acrididae) to crowding and visual stimuli

AbstractThe effects of crowding and isolation on body color and behavior were observed for the mid‐instar nymphs of the desert locust, Schistocerca gregaria. Some of the solitarious (isolation‐reared) nymphs that were crowded for 1 or 4 h during the third instar developed black patterns at the fourth instar, but most individuals remained unaffected. Black patterns appeared in all individuals that were crowded for 1 day or longer, but even after 4 days of crowding the black patterning for some individuals was not as intense as that for the gregarious (crowd‐reared) controls. Isolation of gregarious nymphs caused the black patterns to recede or disappear at the last (fifth) nymphal instar, but it was necessary to isolate the nymphs from the beginning of the first instar to obtain body coloration looking like solitarious nymphs in most individuals. Solitarious nymphs that were allowed to see gregarious nymphs developed different intensities of black patterns depending on the body size and number of nymphs shown. The behavioral phase shift from one phase to another was observed when the nymphs were crowded or isolated for 2 days or longer, as previously reported for the last nymphal instars of the same strain. Behavioral gregarization was induced for isolated nymphs that were allowed to see a group of nymphs through a transparent double wall. These results suggested that body‐color phase shift occurred more rapidly for mid‐instar nymphs than for late instar nymphs but the rate of behavioral phase shift was similar for the two instars.

Predation of nymphal tomato potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), by the predatory mite, Anystis baccarum L. (Trombidiformes: Anystidae)

ABSTRACTThis study investigated predatory behaviour of the mite Anystis baccarum on nymphs of the tomato potato psyllid Bactericera cockerelli. In 30-minute laboratory bioassays, predation rates per individual mite were low if late instar psyllid nymphs were ‘braced’ or ‘sealed’ tightly to a leaf, with only one nymph from twelve being successfully attacked and eaten in the presence of psyllid sugars (wax covered honeydew). However predation rates were approximately six times higher if the nymph was detached from the leaf and inverted. The presence of psyllid sugars had an impact on predation rates because mites would probe or investigate, and often feed from these sugars, sometimes leading to the immediate cessation of the mite’s investigation of the psyllid. Overall, the results of this investigation confirm that these mites consume late instar psyllid nymphs but may need to be at high densities before substantial reductions in psyllids occurred. The mites may be a more effective predator of psyllid eggs or younger instars and this predatory behaviour warrants further investigation.

Freeze tolerance ofCyphoderris monstrosa(Orthoptera: Prophalangopsidae)

AbstractThe great grig,Cyphoderris monstrosaUhler (Orthoptera: Prophalangopsidae), is a large (20–30 mm, &gt;1 g), nocturnal ensiferan that inhabits montane coniferous forests in northwestern North America.Cyphoderris monstrosaoverwinters as a late instar nymphs, but its cold tolerance strategy has not previously been reported. We collected nymphs from near Kamloops, British Columbia, Canada in late spring to determine their cold tolerance strategy.Cyphoderris monstrosanymphs were active at low temperatures until they froze at −4.6±0.3 °C. The nymphs survived internal ice formation (i.e., are freeze tolerant), had a lethal temperature between −9 °C and −12 °C, and could survive for between five and 10 days at −6 °C. IsolatedC. monstrosagut, Malpighian tubules, and metafemur muscle tissues froze at temperatures similar to whole nymphs, and likely inoculate freezingin vivo. Hemolymph osmolality was 358±51 mOsm, with trehalose and proline comprising ~10% of that total. Glycerol was not detectable in hemolymph from field-fresh nymphs, but accumulated after freezing and thawing. The control of ice formation and presence of hemolymph cryoprotectants may contribute toC. monstrosafreeze tolerance and overwintering survival.