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Cautery of the neurosecretory cells of the pars intercerebralis, 48 hrs after feeding, of Panstrongylus megistus fifth instar, prevents the development of the ovaries, and stops the physiological processes that lead to the differentiation of oögonies into primary oöcytes.
Important changes in the amount of neurosecretory material in the A and A' cells of the parsintercerebralis during the fifth instar intermoult of P. megistus occur. The release of neurosecretory material at different moments of intermoult, suggests that the A cells induce mitosis and that meiosis is induced by the release of A' cells material.
Ovarian phenomena of mitosis and meiosis are both under cerebral endocrine control, but their determinism is not the same. The critical period of meiosis coincides with that of the imaginal moult, whereas the critical period of mitosis is precocious. Implants of brains, re-establish the ovarian evolution stopped by electrocoagulation of the pars intercerebralis.
The ecdysone titre in the hemolymph during the two last instars of P. megistus was studied by radio-immunology technique. Changes observed are very similar in both instars. Two peaks of inequal amplitude are present. The first, always lower than the second, occurs at 1/3 of the intermoult whereas the second, distinctly higher, is observed at 2/3 period of the intermoult.
The effects of juvenile hormone (JH) on the control of vitellogenin appearance in the haemolymph of Spilostethus pandurus newly emerged females have been studied as well as their intake by developing oocytes. SDS-PAGE electrophoresis has been used as an analytical method for protein studies. JH induced early detection of vitellogenins in the haemolymph of treated insects and their accelerated incorporation by undeveloped ovaries. The results suggest that JH plays an essential role as a gonadotrophic agent, just as it has been described for other insect species.
The reproductive parameters of Telenomus podisi, Trissolcus brochymenae (Hymenoptera: Scelionidae) and Ooencyrtus sp. (Hymenoptera: Encyrtidae) were studied for three generations on their natural host Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). A parasitism rate of 10 eggs/day/species was used under laboratory conditions of 27 +/- 1 degrees C, 60 +/- 10% RH and 14 h of photophase. No significant differences were detected between generations in terms of net reproductive rate (Ro), intrinsic rate of natural increase (rm), generation time (T) and the effect of doubling time on population increase (DT). However, T. podisi and T. brochymenae had significantly higher Ro and rm values, and lower T and DT values, with rm 1.59 and 1.50 times higher than Ooencyrtus sp., respectively. In addition the former species also had shorter egg-adult period, greater longevity of females and reproduction period than the other species. These results confirm the greater reproductive potential of T. podisi and T. brochymenae, which are commonly found parasitizing P. nigrispinus.
In the testicle of Graphosoma italicum and Eurydema ventralis the histochemical localization of 3-beta-HSD, SDH, MDH and LDH was followed up. The enzymic activity was detected in various stages of the sexual cells; the strongest activity was found in the evoluted spermatids and spermatozoa. As far as the nutritive cells of the testicle are concerned, the reaction of these different enzymes appeared very weak or absent.
The composition and abundance of predatory fauna in corn, Zea mays L., were studied by field visual sampling and pitfall traps over a 5-yr period. In visual samplings, the most abundant groups were Araneae, Heteroptera, Carabidae, Coccinellidae, and Staphylinidae, whereas the prevalent predators caught in pitfall traps belonged to Carabidae, Araneae, Dermaptera, and Opilionidae. The most abundant species or genera in the prevalent groups, except in Arachnida, were identified. Application of the insecticide imidacloprid as a seed dressing is common in the study area to prevent wireworm and cutworm damage. By comparing predator composition and abundance in treated and untreated cornfields during the 5 yr, we assessed the impact of imidacloprid seed treatment on predatory fauna. Among the prevalent predator groups found in visual sampling, Araneae, Coccinellidae, and Staphylinidae were not affected by the imidacloprid treatment, whereas Carabidae was only moderately affected in one of the 5 yr studied. On the contrary, Heteroptera was more drastically reduced by the imidacloprid, but the effect varied with the year. Incidence of European corn borer, Ostrinia nubilalis (Hübner), may be increased as result of such heteropteran reduction. In pitfall traps, only Staphylinidae resulted in lower numbers as consequence of the treatment, whereas the rest of the most abundant predator groups, Carabidae, Araneae, Dermaptera, Opilionidae, Trombididae, and Heteroptera, were not caught in significantly different numbers in treated or untreated plots.
The aggregation pheromone of Riptortus clavatus (Heteroptera: Alydidae) consists of (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H), and myristyl isobutyrate (MI). Experiments were conducted to examine the attraction of Piezodorus hybneri (Heteroptera: Pentatomidae) to the pheromone components of R. clavatus, individually and in combination, and to determine if P. hybneri produces these compounds. Electroantennogram (EAG) responses of P. hybneri to E2HE2H were significant in a dose dependent manner, while those to E2HZ3H were not significantly different from those to hexane and air. Field trapping tests using E2HZ3H, E2HE2H, and MI, individually or in combination, showed that only E2HE2H was attractive to P. hybneri. E2HE2H was not detected in whole-body extracts or volatile collections from either sex of P. hybneri adults. We propose that the response of P. hybneri adults to the R. clavatus aggregation pheromone may be related to finding suitable host plants.
If hot spots for different taxa coincide, priority-setting surveys in a region could be carried out more cheaply by focusing on indicator taxa. Several previous studies show that hot spots of different taxa rarely coincide. However, in tropical areas indicator taxa may be used in selecting complementary networks to represent biodiversity as a whole. We studied beetles (Coleoptera), Heteroptera, polypores or bracket fungi (Polyporaceae) and vascular plants of old growth boreal taiga forests. Optimal networks for Heteroptera maximized the high overall species richness of beetles and vascular plants, but these networks were least favourable options for polypores. Polypores are an important group indicating the conservation value of old growth taiga forests. Random selection provided a better option. Thus, certain groups may function as good indicators for maximizing the overall species richness of some taxonomic groups, but all taxa should be examined separately.
We implemented a 2-yr program to reduce organophosphorus and carbamate insecticide use and mitigate their associated risks as they relate to peach production in New Jersey and elsewhere. The main thrust integrated mating disruption with ground cover management practices to reduce oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae), abundance and damage. This Reduced Risk Peach Arthropod Management Program was compared with adjacent conventionally managed peach orchards. In 1999, we found 2.3 times fewer L. lineolaris and stink bugs (Euschistus servus (Say), E. tristigmus (Say), Acrostemum hilare (Say) (Heteroptera: Pentatomidae) and 2.0 times less heteropteran damaged peaches in reduced-risk orchards when compared with conventionally managed orchards. In 2000, we observed 4.9 times fewer heteropteran insects in reduced-risk orchards but damage levels were not significantly different between the two programs. In both years, G. molesta mating disruption gave at least 4 mo of noninsecticidal control of this major pest. The reduced-risk program provided a level of pest control that was equal to or better than conventional peach pest management programs while using fewer organophosporus and carbamate insecticides.
Homoptera and Heteroptera comprise a large insect assemblage, the Hemiptera. Many of the plant sap-sucking Homoptera possess unusual and complex life histories and depend on maternally inherited, intracellular bacteria to supplement their nutritionally deficient diets. Presumably in connection with their diet and lifestyles, the morphology of many Homoptera has become greatly reduced, leading to major controversies regarding the phylogenetic affiliations of homopteran superfamilies. The most fundamental question concerns whether the Homoptera as a whole are monophyletic. Recent studies based on morphology have argued that the Homoptera Sternorrhyncha (Aphidoidea, Coccoidea, Psylloidea, Aleyrodoidea) is a sister group to a group comprising the Homoptera Auchenorrhyncha (Fulgoroidea, Cicadoidea, Cercopoidea, Cicadelloidea) and the Heteroptera, making the Homoptera paraphyletic. We sequenced the 5' 580-680 base pairs of small-subunit (18S) ribosomal DNA from a selection of Homoptera, Hemiptera, and their putative outgroups, the Thysanoptera and Psocoptera, to apply molecular characters to the problem of Homoptera phylogeny. Parsimony, distance, maximum-likelihood, and bootstrap methods were used to construct trees from sequence data and assess support for the topologies produced. Molecular data corroborate current views of relationships within the Sternorrhyncha and Auchenorrhyncha based on morphology and strongly support the hypothesis of homopteran paraphyly as stated above. In addition, it was found that Homoptera Sternorrhyncha have extra, GC-rich sequence concentrated in a variable region of the 18S rDNA, which indicates that some unique evolutionary processes are occurring in this lineage.
In the field, a multitude of species can be exposed to numerous toxicants; thus, the sensitivity of individual species to particular toxicants must be known to predict effects and to analyze changes in species composition. For most species, no information about their toxicant sensitivity is available. To address this limitation, we have grouped the available information to assign sensitivities to aquatic invertebrate taxa relative to Daphnia magna. With respect to organic compounds, most taxa of the orders Anisoptera, Basommatophora, Coleoptera, Decapoda, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Hirudinea, Isopoda, Oligochaeta, Prosobranchia, Trichoptera, Tricladida, and Zygoptera are less sensitive than D. magna. Some taxa of the Amphipoda, Plecoptera, and Cladocera (other than D. magna) are significantly more sensitive. For organic compounds, approximately 22% of the investigated taxa were more sensitive than D. magna. Most taxa of the orders Amphipoda, Basommatophora, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Isopoda, Oligochaeta, and Tricladida are significantly less sensitive than D. magna to metal compounds. The taxa belonging to the Crustacea, with the exception of the order Isopoda, are much more sensitive. For metal compounds, approximately 30% of the investigated taxa were more sensitive than D. magna. Hence, D. magna is among the most sensitive taxa regarding both groups of toxicants. The sensitivities for several taxa are listed, and use of the relative sensitivity distribution to link toxicant effects in mesocosm studies and field investigations is discussed.
The effects of juvenile hormone and precocoene II on the metabolic rate of Blattela germanica L. (Blattaria, Blattellidae), Spilostethus pandurus Scop. (Heteroptera: Lygaeidae) and Oncopeltus fasciatus Dallas (Heteroptera: Lygaeidae) 5th instar nymphs and adults have been investigated. Direct volumetric method was used to determine the oxygen consumption rate. JH produced a stage and/or sex dependent increase in the metabolic rate according to the species considered. On the other hand, PII decreased oxygen consumption in Blattella germanica and S. pandurus fifth instar and males, whereas O. fasciatus metabolic rate was not affected by the treatment.
A 171,000 M(r )polypeptide of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) that constituted 16% of the protein in eggs also constituted up to 25% of the protein in hemolymph of fed females. It was identified as the major or sole apoprotein of vitellogenin. Eggs contained major polypeptides of 171, 106, and 51 kDa. The hemolymph polypeptide was identified with a polypeptide (vitellin) in egg extracts by comparing molecular weights, specificity of occurrence in fed females, and immunological reactivities. Females, starved for 5 days after eclosion to assure complete previtellogenic development, produced vitellogenin within a day after feeding on larval Galleria mellonella, and within 4 days after feeding on an artificial diet. Appearance of vitellogenin preceded ovarian growth by 2-3 days. Two monoclonal antibodies raised against egg proteins of P. maculiventris were selected for their strong reaction against egg extract and female hemolymph and null reaction against male hemolymph. Only one 170-kDa band in egg and hemolymph reacted with the antibodies on denaturing Western blots. These monoclonal antibodies are being used to develop an enzyme-linked immunosorbent assay (ELISA) to quantitate reproductive response of females to diets of differing quality.
Improvement of an existing meat-based diet has been obtained for rearing the generalist predator Dicyphus tamaninii (Heteroptera: Miridae). The approach followed, different from the classical addition/deletion method, was performing biochemical analysis of adult carcasses in order to have information about the nutritional status of the predator. Comparison of total, free amino acids and lipid composition of meat-reared and conventionally reared females allowed detecting some nutritional deficiencies. A reformulated diet with new sources of proteins and lipids was tested again with the predator. Some biological parameters of bugs that were inferior in the initial meat diet when compared with those of the conventionally reared insects, such as nymphal development time and fresh weight, have been improved with the reformulated diet.
The lethal doses of the pyrethroid deltamethrin were estimated for the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae), and the sub-lethal effects of an LD25 on female walking behaviour were evaluated. Linear speed of treated parasitoids was reduced compared with that of untreated ones for a period of up to 24 h. The sub-lethal effects of deltamethrin on parasitoid response to patches contaminated by a contact kairomone from its host, Nezara viridula L (Heteroptera: Pentatomidae), was also evaluated. Both treated and untreated parasitoids responded to host-contaminated patches by increasing residence time and decreasing linear speed. However, treated females showed a significantly lower residence time compared with untreated females. Both treated and untreated females showed a similar decrease over time in the proportion of time spent in the host-contaminated patch. Hence, we hypothesise that the sub-lethal effect of deltamethrin on host foraging may decrease T basalis efficacy in controlling N viridula.
In plant bugs (Miridae), females produce sex pheromones in the metathoracic scent gland, which in most other true bugs (Heteroptera) is responsible for chemical defense. The possibility that the metathoracic gland secretion of male plant bugs plays a role other than defense has been largely overlooked. Here we show that in a pine-inhabiting mirid, Phytocoris difficilis Knight, hexyl butyrate and ( E)-2-hexenyl butyrate are abundantly produced only in males; we demonstrate that these metathoracic gland compounds elicit strong antennal responses in conspecific males, and that these butyrates totally interrupt attraction of males to the female-produced sex pheromone. Our results suggest that in at least some plant bugs the male metathoracic scent gland esters have a natural communicative function as anti-sex pheromones, probably to interrupt further mating attempts by other males.