Host plant toxins and unpalatability of Neacoryphus bicrucis (Hemiptera: Lygaeidae)

Abstract. 1. Host plant choice of the seed bug, Neacoryphus bicrucis Say (Hemiritera, Lygaeidae), was evaluated in four different Georgia habitats. N. bicrucis utilized only species of Senecio as host plants at a granite outcrop and at old fields on the coastal plain, in the piedmont, and in the Blue Ridge Mountains.
2. In laboratory tests N. bicrucis is distasteful to the green anole lizard, Anolis carolinensis Voight. Only six of ninety field-collected bugs were eaten in palatability trials while eighty-four of the remaining ninety attacked bugs were rejected by lizards without apparent harm. However, the bugs were palatable to Fowler's toads, Bufo woodhousei fowleri Hinckley, which ate all thirty-six bugs offered to them.
3. N. bicrucis selectively sequesters pyrrolizidine alkaloids from Senecio spp. These may cause the insects' distastefulness to green anoles. In palatability trials, lizards ate all twenty insects reared on sunflower seeds, Helianthus annus, but rejected all twenty reared on Senecio smallii.     

Evolutionary causes of male-biased sexual size dimorphism from a female perspective in the seed bug Togo hemipterus (Heteroptera: Lygaeidae)

Sexual size dimorphisms (SSDs) in body size are expected to evolve when selection on female and male sizes favors different optima. Many insects show female-biased SSD that is usually explained by the strong fecundity advantage of larger females. However, in some insects, males are as large as or even larger than females. The seed bug Togo hemipterus (Scott) also exhibits a male-biased SSD in body size. Many studies that have clarified the evolutionary causes of male-biased SSD have focused only on male advantages due to male–male competition. To clarify the evolutionary causes of male-biased SSD in body size, we should examine the degree of not only the sexual selection that favors larger males but also natural selection that is acting on female fecundity. The obtained results, which showed higher mating acceptance rates to larger males, implies that females prefer larger males. No significant relationship was detected between female body size and fecundity; body size effects on female fecundity were weak or undetectable. We conclude that male-biased SSD in T. hemipterus can be accounted for by a combination of sexual selection through male–male competition and female choice favoring large males, plus weak or undetectable natural selection that favors large females due to a fecundity advantage.     

Males of the seed bug Togo hemipterus (Heteroptera: Lygaeidae) use accessory gland substances to inhibit remating by females

In species in which females mate repeatedly, males can adopt several strategies to reduce the risk of sperm competition with future males. The refractory period of females significantly increased as the mating duration increased in the seed bug Togo hemipterus (Heteroptera: Lygaeidae). To elucidate the mechanisms by which mated females are inhibited from remating, we investigated the effects of male-derived substances on the inhibition of mating receptivity of virgin females by injecting the substances into their abdomens. The length of time from injection to mating in virgin females was significantly longer for females injected with accessory gland B solution than for those injected with seminal vesicle, accessory gland A, or control solutions. This is the first report showing that heteropteran males inhibit female remating by using substances from an accessory gland. We discuss and consider the adoption and evolution of this strategy by T. hemipterus males by focusing on female genitalia structures, oviposition habit, and paternity and comparing these traits with those of other heteropterids.     

Pharmacological observations on body fluids from the milkweed bug,Oncopeltus fasciatus (Dallas) (Heteroptera: Lygaeidae)

A report is given on the pharmacological activity of body fluids from milkweed bugs maintained on a diet of sunflower seeds, together with observations on the toxin accumulating system of the adult insect.     

Effect of day length on development and reproductive diapause in Nysius huttoni White (Heteroptera, Lygaeidae)

Abstract:  Nysius huttoni White is endemic to New Zealand and an important pest of wheat and brassica crops. To provide critical information for pest forecast, management and quarantine inspection, we investigated the effect of day length on the growth, development and reproductive diapause of this pest under a series of photoperiodic regimes: 16 : 8, 14 : 10, 12 : 12 and 10 : 14 h [light : dark (L : D)]. Long day lengths [16 : 8 and 14 : 10 h (L : D)] promote a continuous lifecycle while short day lengths [12 : 12 and 10 : 14 h (L : D)] slow up the growth and development, prolong the pre-mating period, and induce the reproductive diapause. The absence of oviposition for approximately 30 days is recognized as the criterion for N. huttoni reproductive diapause definition. When all life stages are kept under the short day length conditions, only 60–73% of females enter reproductive diapause; if the exposure to short day lengths starts in late instar nymphs, 100% of females enter reproductive diapause. If only adults experience short day lengths, does diapause incidence fall in between, with up to 26% of females laying a few eggs before entering diapause. The critical photoperiod for the induction of reproductive diapause falls between 13.3 : 10.7 and 13.5 : 10.5 h.     

Ecological significance of the wing polymorphism of the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

The wing polymorphism of the oriental chinch bug, Cavelerius saccharivorus, was studied in relation to its reproductive strategy. The frequency distribution of wing form in terms of the relative wing length (R.W.L.) changed with increase in the population density from a single modality biased toward the brachypterous form to bimodality with both macropterous and more extreme brachypterous forms. Since some evidences in the field showed that fliers are limited to macropters, such a bimodality of wing form indicated that C. saccharivorus employs a mixed strategy with some portion of adults staying on in the same habitat, whereas the rest disperse. Moreover, macropters were larger in body size than brachypters emerging in high density populations, although smaller than brachypters emerging in low density populations. Larger body size as well as the delay of ovarian maturation in macropters was considered to be a beneficial trait for migratory behaviour.     

Seasonal occurrence and diapause induction of a predatory bug Andrallus spinidens (F.) (Heteroptera: Pentatomidae)

The bug Andrallus spinidens (F.) (Heteroptera: Pentatomidae) is a polyphagous predator of insect larvae, which is distributed in tropical and warm temperate zones worldwide. Seasonal occurrence and diapause induction of this bug were studied in a population in Miyazaki, southern Kyushu, Japan. The field research showed that A. spinidens produces three or four generations a year and is most abundant from mid‐summer to autumn. Reproductive activity of field‐collected adults decreased from late summer to autumn, indicating that this bug enters adult diapause in autumn. Only adults were found in early spring and these were reproductive. Laboratory experiments showed that, irrespective of photoperiod, adult diapause is induced at lower temperatures (≤22.5°C), whereas it is avoided at higher temperatures (≥25°C). Ambient temperature falls across the critical range from late summer to autumn. Thus, the bug clearly overwinters in adult diapause induced by low temperatures and this diapause is terminated during the course of winter.     

Nymphs of Cymus novaezelandiae (Heteroptera: Lygaeidae)

Abstract

The 3rd-, 4th-, and 5th-instar nymphs of Cymus novaezelandiae Woodward are described; the dorsal aspect of the 5th instar is illustrated.     

Reproduction and egg diapause of the oriental chinch bug,Cavelerius saccharivorus okajima (Heteroptera: Lygaeidae), in the subtropical winter season in relation to its wing polymorphism

Reproduction and egg diapause of the oriental chinch bug, Cavelerius saccharivorus, in the subtropical winter season were investigated in relation to its wing polymorphism. Macropterous females collected from the southern part of Okinawa Is. in the autumn season delayed their oviposition and were less fecund early in the adult life period, but survived much longer than brachypterous females collected from the same locality. The total fecundity was not significantly different between wing morphs. The diapause of eggs laid by brachypters tended to be terminated more easily at a high temperature than that of eggs laid by macropters. This indicated that the eggs laid by macropters were more intense in their diapause than those laid by brachypters. However, irrespective of the parental wing form, diapause showed considerable variation in its intensity within and between clutches.     

Characterization of an obligate intracellular bacterium in the midgut epithelium of the bulrush bug Chilacis typhae (Heteroptera, Lygaeidae, Artheneinae)

Many members of the suborder Heteroptera have symbiotic bacteria, which are usually found extracellularly in specific sacs or tubular outgrowths of the midgut or intracellularly in mycetomes. In this study, we describe the second molecular characterization of a symbiotic bacterium in a monophagous, seed-sucking stink bug of the family Lygaeidae (sensu stricto). Chilacis typhae possesses at the end of the first section of the midgut a structure which is composed of circularly arranged, strongly enlarged midgut epithelial cells. It is filled with an intracellular endosymbiont. This "mycetocytic belt" might represent an evolutionarily intermediate stage of the usual symbiotic structures found in stink bugs. Phylogenetic analysis based on the 16S rRNA and the groEL genes showed that the bacterium belongs to the Gammaproteobacteria, and it revealed a phylogenetic relationship with a secondary bacterial endosymbiont of Cimex lectularius and free-living plant pathogens such as Pectobacterium and Dickeya. The distribution and ultrastructure of the rod-shaped Chilacis endosymbiont were studied in adults and nymph stages using fluorescence in situ hybridization (FISH) and electron microscopy. The detection of symbionts at the anterior poles of developing eggs indicates that endosymbionts are transmitted vertically. A new genus and species name, "Candidatus Rohrkolberia cinguli," is proposed for this newly characterized clade of symbiotic bacteria.     

Ecology of Oxycarenus species (Heteroptera: Lygaeidae) in southern Ghana

The ecology of three species of Oxycarenus , a heteropteran bug, was studied in southern Ghana. Host plants are listed. Seasonal changes in populations were followed in two species ( O. fieberi and O. hyalinipennis ), both of which frequent malvaceous host plants that flower throughout the year. The third species ( O. dudgeoni ) shows successional colonization of host plants since its hosts include trees which have restricted flowering seasons. Experiments on host preference showed that in all three species, cotton ( Gossypium hirsutum : Malvaceae) is either preferred or enjoys equal preference with their principal feral host plants. The natural enemies of Oxycarenus , and the defensive mechanisms against them, are also described.     

Genetic variation of density responses in relation to wing polymorphism in the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

Responses to nymphal density in the determination of wing form were compared between the offspring from brachypter x brachypter crosses and those from macropter x macropter crosses of the oriental chinch bug, Cavelerius saccharivorus. In the offspring from crosses between macropters, there was a strong tendency for macropters to increase to a rather high level with increasing nymphal density in both sexes. In contrast to this, in the offspring from crosses between brachypters, the appearance rate of macropters attained a maximum value in moderately crowded conditions and conversely decreased to a lower level in more crowded conditions in both sexes. Thus density response patterns concerning the determination of wing form were quite different between the offspring from different crosses in the wing form, indicating that there is a genetic basis underlying wing polymorphism in this species. As for the body size of emerged adults, macropters tended to be larger than brachypters in the same crowded condition. Moreover, the rate of decrease of body size with nymphal density was lower in the offspring from crosses between macropters than in the offspring from crosses between brachypters. This indicated that the former offspring are more tolerant of nymphal crowding than the latter. The difference in such a tolerance against nymphal crowding between the offspring from different crosses was considered to be related to the difference in the appearance of macropters in the crowded conditions between them.     

Membranes and calcium sequestration during spermiogenesis in the cotton seed bug (Dysdercus intermedius: Heteroptera)

Summary By use of osmium ferricyanide (OsFeCN) staining the fate of cytoplasmic membranes was followed during spermiogenesis in the cotton seed bug (Dysdercus intermedius). During early spermiogenesis interzonal lamellae of endoplasmic reticulum become aggregated as a stack of membranes traversing the entire cell body from the nucleus to the cytoplasmic bridge connecting neighbouring spermatids. Cisternae of endoplasmic reticulum ensheath the acroblast from which vesicles of different sizes are pinched off into the cytoplasm. The oxalate method was used to show that acroblast and associated vesicles are calcium-sequestering sites in spermatids. Membrane profiles with dense calcium oxalate precipitate derived from the acroblast form an uninterrupted membranous sheath at the apical side of the nucleus where the proacrosome will be attached. With further development of the spermatids, the vesicles derived from the acroblast also participate in forming a calciumsequestering sheath enveloping the axoneme and the mitochondrial nebenkern derivatives.     

Mating aggregation of a stink bug,Megacopta punctissimum (Montandon) (Heteroptera: Plataspidae)

Summary Adults of a stink bug,Megacopta punctissimum, form aggregations on stems of the bush-clover,Lespedeza crytobotria, in spring. They do not oviposit there, but feed and mate within aggregations. Oviposition is made on other leguminous plants such as the kudzu-vine,Pueraria lobata. Mean size of aggregations (groups of two or more individuals which sit on a stem at distance less than 3 cm from their nearest neighbors) consisted of 4.4 individuals. The sex ratios within aggregations were similar to overall sex ratio of the population including solitary individuals (0.58). More than 50% of females found in aggregations were copulating. Percentage of femalesin copula in larger aggregations was higher than that in smaller aggregations, and this difference was considered to be caused by the higher chance of sexual enconters in larger aggregations. It was suggested that the aggregation of this species on the bush-clover is not a ‘harem’ (a male monopolizes a group of females reported in some other stink bugs) but is mating aggregation to raise the chance of mating. This work was partially supported by Grant-in-Aid (No. 56480039) from the Ministry of Education, Science and Culture.     

Seed Bugs (Heteroptera,Lygaeidae) of the Northeast of European Russia

Entomological Review - An annotated list of seed bugs (Heteroptera: Lygaeidae) of the Northeast of European Russia is presented, comprising 36 species from 22 genera of 7 subfamilies and...     

Reproductive properties of the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae), in relation to its wing polymorphism

Reproductive properties of the oriental chinch bug, Cavelerius saccharivorus, were investigated for three types of female adults: brachypters produced in both high and low density populations and macropters produced in high density populations. With respect to egg-laying potential in terms of clutch size, clutch number, and total fecundity, macropters were superior to brachypters produced in the same high density population, although inferior to brachypters produced in the low density population. The mean fecundity of female adults in each type was positively correlated with mean body length. Macropterous females markedly prolonged their initiation of both copulation and oviposition and had a much longer life span compared with both types of brachypters. However, there was no fundamental difference in reproductive schedules between the two types of brachypters.     

Saugverhalten und Nahrungsaufnahme von Oncopeltus fasciatus Dallas (Heteroptera,Lygaeidae)

Zusammenfassung Das Verhalten von Oncopeltus fasciatus bei der Nahrungssuche und- aufnahme wurde untersucht. Durch Aufspeicheln und Aufsaugen von Speichelsekret wird ein Substrat auf Eignung für Einstich und Nahrungsaufnahme geprüft. Die histologische Bearbeitung des Saugortes in einer Pflanze (Vicia faba) zeigt eine deutliche Bevorzugung des Leitungssystems beim Einstich. Hier werden Speichelscheiden gebildet. Im Samen (Asclepias syriaca und Helianthus annuus) werden die reservestoffreichen Cotyledonen besaugt. Der Einstich erfolgt ohne Sekretion einer Speichelscheide. Die Funktion dieser Speichelscheide wird diskutiert. Unter extremen Bedingungen tritt bei der sonst phytophagen Wanze trotz ihres ausgeprägten Subsozialverhaltens Kannibalismus auf. Beim Durchstechen der Cuticula dürften überwiegend mechanische Kräfte wirksam sein. Im Speichel konnte kein Chitin-spaltendes Enzym nachgewiesen werden. Weiterhin wurde die Saugzeitenverteilung zwischen Pflanze (Wasseraufnahme) und Samen (Nahrungsaufnahme) über einen Tagesablauf bestimmt. Die Wanzen dürften an der Pflanze in kürzeren Saugphasen Sättigung erreichen als an den dehydratisierten Samen. Die beträchtliche Menge and Speichel (1,14 mg/Wanze/Std), die in einen Samen injiziert werden, emulgieren und suspendieren dessen Inhalt und bringen ihn so in eine für das Insekt aufsaugbare Form.

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Summary The feeding behaviour of Oncopeltus fasciatus has been investigated. Exploration of food materials is performed by means of watery saliva which is secreted onto surfaces of substrates and sucked back again. Histological tests indicate that the animal preferably pierces the conducting system of the Vicia faba plant. Oncopeltus fasciatus secretes sheath material which coagulates and forms a lining to the path of the stylets during plant feeding. Feeding on seeds (Asclepias syriaca and Helianthus annuus) is not accompanied by stylet sheath formation. The function of this stylet sheath is discussed. Under extreme conditions the phytophagous animal shows cannibalism in spite of its marked subsocial behaviour. Penetration of the cuticle seems to be effected mainly by mechanical forces. No chitin-splitting enzyme could be detected in the saliva. The feeding activity over a photoperiod of 12 hrs on plants (uptake of water) and seeds (uptake of nutritive materials) is determined. It is suggested that on a green plant the animal is saturated more rapidly than on dehydrated seeds. The considerable amounts of watery saliva emulsify and suspend the contents of the seeds. Into seeds of Asclepias syriaca saliva is injected at a rate of approximately 1.14 mg/animal/hr.

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Durchgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft im Rahmen einer Herrn Prof. Kloft gewährten Sachbeihilfe.     

Cytogenetics of the true bug infraorder Cimicomorpha (Hemiptera, Heteroptera): a review

The Cimicomorpha is one of the largest and highly diversified infraorders of the Heteroptera. This group is also highly diversified cytogenetically and demonstrates a number of unusual cytogenetic characters such as holokinetic chromosomes; m-chromosomes; multiple sex chromosome systems; post-reduction of sex chromosomes in meiosis; variation in the presence/absence of chiasmata in spermatogenesis; different types of achiasmate meiosis. We present here a review of essential cytogenetic characters of the Cimicomorpha and outline the chief objectives and goals of future investigations in the field.     

A novel adipokinetic peptide in a water boatman (Heteroptera, Corixidae) and its bioanalogue in a saucer bug (Heteroptera, Naucoridae)

The corpora cardiaca (CC) of two water bug species, the water boatman Corixa punctata and the saucer bug Ilyocoris cimicoides, contain a substance that cause hyperlipemia in the migratory locust. The primary sequence of one octapeptide belonging to the adipokinetic hormone (AKH)/red pigment-concentrating hormone (RPCH) family was deduced from the multiple MS(N) electrospray mass data of CC material from each species. Whereas the saucer bug contains the known octapeptide pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Anaim-AKH, the water boatman has a novel peptide identified as pGlu-Leu/Ile-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Corpu-AKH. The ambiguity about the amino acid at position 2, i.e. Leu or Ile, in Corpu-AKH was solved by isolating the peptide in a single-step by reversed-phase HPLC and establishing co-elution with the synthetic peptide containing Leu at position 2. Functionally, the peptides regulate lipid mobilization, as evidenced by an adipokinetic effect after injecting synthetic Anaim-AKH and Corpu-AKH into the respective acceptor species. Swimming activity of I. cimicoides also causes hyperlipemia.