An investigation of the possible presence of an aggregation pheromone in the milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii

ABSTRACT. The presence of an aggregation pheromone was studied in two species of milkweed bugs. The nymphs, young adults and old adults of Oncopeltus fasciatus were tested for their aggregation in response to acetone extracts of themselves and each other. The O. fasciatus nymphs were also tested for their response to odour from live O. fasciatus nymphs, as well as to Lygaeus kalmii nymphal extract, and the response of L. kalmii nymphs towards O. fasciatus nymph extract was tested. It was found that there is an aggregation pheromone in the nymphs and young adults and that there may be an alarm pheromone in the old adult O. fasciatus. A preliminary chemical analysis performed on the aggregation pheromone revealed it probably to be a polar non-aromatic compound of high molecular weight.     

Quantitative food utilization and reproductive allocation by adult milkweed bugs, Oncopeltus fasciatus

ABSTRACT. Age-specific and lifetime dry mass budgets were estimated for mated and virgin adult milkweed bugs, Oncopeltus fasciatus (Dallas) Hemiptera: Lygaeidae), fed air-dried milkweed seeds ( Asclepias syriacd ) in the laboratory at LD 14:10 and 23°C. Relative consumption rate (RCR) of all bugs was high during the first 8 days posteclosion (teneral period) as their fresh weight, dry weight, and fat content increased. Thereafter, the physiological syndrome associated with reproduction in mated females was indicated by their higher RCR, earlier and greater rate of egg production, greater lifetime relative metabolic rate and higher net and gross production efficiencies than virgin females and males. Males tended to live longer than virgin and mated females, which had similar lifespans. Mated females weighing less at eclosion remained lighter in weight on the day of mean peak weight, but food consumption, egg production and lifespan were independent of body-weight over a 25% range. Input of nymphal reserves or male reproductive secretions to egg production is probably minor in comparison with the adult female's food budget. The high proportion of the food budget allocated to egg production by mated females of O.fasciatus is consistent with its migratory, colonizing lifestyle.     

Diel organization of behaviour in milkweed bugs, Oncopeltus spp.

ABSTRACT. Daily cyclic activities in various behaviours were similar in three species of tropical Oncopeltus (Heteroptera, Lygaeidae). Opposition in females and general movement in both sexes peaked in the middle to late light period. In contrast, feeding and mating peaked at the end of the light period and the beginning of the dark respectively. Other behaviours also tended to display one or the other of these patterns. The diel timing of behaviour observed in this study essentially duplicated the periodicities of a migratory population of Oncopeltus fasciatus from Iowa. The similarity of results across species and populations suggests a general pattern for the genus which probably serves to synchronize behaviours with environmental cycles and appropriate physiology. This similarity is interesting in view of the broad geographical range of the genus across both temperate zone and tropics and in view of the differences among populations with respect to photoperiodic determination of diapause.     

Responses in flight to selection on wing length in non-migratory milkweed bugs, Oncopeltus fasciatus

A sample of nonmigratory Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae) from Puerto Rico was subjected to bi-directional selection for wing length for 20 generations. Response to selection was strong in both directions. In the 8th and 14th generations samples were drawn from the selected lines and tested for tethered flight. There was little flight observed and no correlation between wing length and flight duration. There was also no correlation between wing length and fecundity. These results contrast with results from a migratory population from Iowa, U.S.A. where there were positive genetic correlations between wing length and both flight and fecundity. A migration-life history syndrome was thus apparent in the migratory Iowa population, but was not present in the non-migratory population from Puerto Rico.

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Résumé L'étude de la relation entre la longueur de l'aile, le vol et la fécondité a été faite sur une population sédentaire d'O. fasciatus de Porto Rico; les résultat ont été comparés à ceux d'une population migratrice de L'Iowa, U.S.A. Les punaises de Porto Rico ont été sélectionnées pour leurs ailes longues ou countes pendant 20 générations, en utilisant des lignées répétitives. Une forte réponse a été obtenue par rapport aux témoines des lignées non sélectionnées. Aux 8ème et 14ème générations de sélection, des punaises ont été prélevées pour examen de leur vol entravé. Très peu de vols ont été obtenus et il n'y avait aucune corrélation entre la durée du vol et la longueur de l'aile. Parallèlement, la fécondité pendant les 5 premiers jours de reproduction a été mesurée, et aucune corrélation n'a été mise en évidence, mais il n'y avait pas non plus de corrélation entre longueur de l'aile et fécondité. Ces résultats différent de ceux de la population migratrice de l'Iowa, pout laquelle il y avait une corrélation génétique positive entre longueur de l'aile, vol et fécondité. Chez les punaises de l'Iowa, il y aurait ainsi un syndrome biologique de migration avec des ailes longues, une fécondité élevée précoce et des vols de longue durée. II n'y avait pas de manifestation de ce syndrome chez les populations sédentaires de Porto Rico. Les O. fasciatus migrateurs et sédentaires différent évidemment par la base génétique de leur biologie.

     

Regeneration of appendages in the large milkweed bug, Oncopeltus fasciatus

An analysis was made of the regeneration of legs and antennae of Oncopeltus. Amputations were performed on first instar larvae within 24 hr after hatching, and on later instars within 24 hr after ecdysis. The resulting regenerates were then measured at each instar. When amputations were performed soon after hatching, there was no significant effect on the duration of any instar. The regenerate was usually visible after the second post-operative ecdysis, and was smaller than a normal appendage (hypomorphic). Removal of the three distal segments of the antenna usually resulted in regeneration of only one segment which was abnormally long and showed a combination of the bristle patterns characteristic of the two most distal segments of the control. In a few such cases a partial intersegmental membrane was present in the regenerated segment. Removal of the tarsus resulted in a structurally complete regenerate which was smaller than the control tarsus. The largest leg regenerates were obtained when amputation was performed through the tibia. With amputation through the femur, a decrease in length of the remainder of this segment was observed after the first ecdysis. This type of amputation and amputation through the trochanter in some cases resulted in the formation of a globular stump containing tarsal claws. The results indicate that amputation of part of an appendage in Oncopeltus does not stimulate an increased growth rate in the stump, but merely causes reorganization of the stump material which subsequently grows at the normal rate. Since even the most hypomorphic regenerates contained well-formed claws, even though proximal parts were missing, it appears that the reorganization process must begin at the most distal point and proceed proximally.     

An energetic analysis of host plant selection by the large milkweed bug,Oncopeltus fasciatus

Summary The large milkweed bug, Oncopeltus fasciatus, is a specialized seed feeder that has been observed completing nymphal development in the field on only a small proportion of its potential host species within the genus Asclepias. In central Missouri only two of the six milkweed species studied, A. syriaca and A. verticillata, commonly supported nymphal O. fasciatus growth in the field. The seed of all six species, however, was equally suitable food for bugs reared in the laboratory. In laboratory preference tests, adult bugs chose to feed on the largest seeds, A. hirtella, but such a preference could not explain the observed field feeding patterns.One explanation to account for the observed host plant selection is based upon an energetic analysis. Only A. syriaca provided enough seed biomass for a clutch of O. fasciatus nymphs to develop on a single plant, and only A. verticillata grew in high enough density that a clutch could find sufficient food within the limited range of nymphal movement. These results illustrate a corollary of the resource concentration hypothesis: within a plant group whose members share similar secondary plant chemistries, the only species that will be viable hosts for a specialized herbivore are those that provide the minimal resource density necessary for the completion of nymphal development.In central Missouri, O. fasciatus has specialized on a critical resource density, not traits of individual Asclepias species. The appearance of host selection within the potential host plant spectrum is the result of a characteristic growth form, seed output, and dispersion pattern for each milkweed species that makes some species much more likely than others to produce sufficient seed resources.     

Intercalary leg regeneration in the large milkweed bug Oncopeltus fasciatus.

Grafting operations were performed on the metathoracic legs of fourth instar Oncopeltus fasciatus within 24 hr after ecdysis. Different levels along the tibia were combined so that a lengthened tibia, approximately 1.5 times the normal length, or a shortened tibia, about half the normal length, were created. Intercalary regeneration occurred between the graft and stump in both combinations and the extra tissue was visible on the adult leg. The intercalary regenerate produced by the lengthened tibia showed reversed bristle polarity, while that produced in the shortened segment showed normal polarity. It is suggested that a regenerate with reversed polarity represents a mirror image duplication of the graft and might originate from the graft, whereas a regenerate with normal polarity may originate, as in normal regeneration, from the stump. It appears that each level in the appendage has the developmental capacity to produce only more distal structures. This conclusion is supported by the results of a grafting operation in which a portion of the tibia was grafted back on to the stump with its proximo-distal axis reversed. Regeneration of appropriate distal structures proceeded from the free proximal surface of the grafted tibia.     

Identification of the adipokinetic hormone of the large milkweed bug Oncopeltus fasciatus

Abstract The adipokinetic hormone (AKH) of the large milkweed bug Oncopeltus fasciatus is isolated from an acidified methanolic extract of 200 corpora cardiaca, purified by single step reversed phase high‐performance liquid chromatography (HPLC) and N‐terminally deblocked using pyroglutamate aminopeptidase. The sequence is identified by Edman degradation and matrix assisted laser desorption/ionization‐time of flight mass spectroscopy as pGlu‐Leu‐Asn‐Phe‐Ser‐Pro‐Asn‐Trp amide. This structure is confirmed by chemical synthesis and coelution of native and synthetic peptide on HPLC. The AKH of O. fasciatus is identical to Tenmo‐HrTH, a member of the adipokinetic/red pigment‐concentrating hormone peptide family that had been isolated earlier from several tenebrionid beetles. Tenmo‐HrTH causes a significant rise in the concentration of haemolymph lipids when injected into adult male and female O. fasciatus, but displays no hyperglycaemic activity. There is no indication of the presence of other AKHs in O. fasciatus. The large milkweed bug represents the first member of the seed bugs (Lygaeidae) for which the endogenous AKH has been identified.     

Feeding, nutrient flow, and digestive enzyme release in the giant milkweed bug, Oncopeltus fasciatus

Abstract.  The giant milkweed bug, Oncopeltus fasciatus , is an intermittent feeder, spending most of its time in compact groups away from the food, with feeding bouts lasting 30–60 min. They macerate a small area of the seed with their stylets, secreting large amounts of saliva (which suspends and emulsifies the seed tissue), and quickly suck the emulsion into the gut. Therefore, little digestive activity occurs in the seed tissue. Freshly ingested food in the first gut region (V1) consists of 50% water, 46% lipid, 5% protein, and 1% soluble carbohydrates. The junction of the midgut and hindgut lacks a lumen in the larvae stages, and a 3 μL large oil drop (> 85% triacylglycerides) accumulates in the third gut region (V3). Approximately 24 h after the imaginal moult, this large volume of oil and faeces is defecated, and thereafter an oily faeces is defecated several times daily. It is postulated that the delayed egestion in larvae protects them against suffocation due to self-soiling with oily faeces. Serine proteases are absent in the gut and, instead, a cystein proteinase, inhibited by E64, is present (gut pH 6.0). High lipase activity was found throughout the gut, but only limited amylase activities. Basal levels of all three enzymes occurred throughout the gut, but at lower levels in starved bugs. Salivary gland extracts contain a cysteine proteinase and a lipase, but no amylase.     

Vitellogenesis in the milkweed bug,Oncopeltus fasciatus Dallas (Hemiptera). A light and electron microscopic investigation

Histochemical and electron microscopic methods have revealed that there are four types of cell inclusions in the late vitellogenic oocytes of Oncopeltus. (a) Type 1 is a vacuole which seems to be contributed from the tropharium via the nutritive tubes. It is suggested that this type consists partly at least of nucleolus-like material (ribonucleoprotein) emitted from the nuclei of the Zone III trophocytes. (b) Type 2 is lipid yolk which in early stage oocytes seems to be produced in the “Balbiani body.” In the vitellogenic oocytes these lipid spheres are apparently imported by the oocyte from the haemolymph either through the follicle cells, or through the extracellular space in the follicular epithelium. (c) Type 3 is carbohydrate/protein yolk where at least part of the protein (“vitellogenic protein”) is taken up from the haemolymph, transported through the extracellular space in the follicular epithelium, and deposited into the oocyte by pinocytosis. (d) Glycogen is deposited from the early phases of vitellogenesis. The tropharium may contribute, besides Type 1 vacuoles, ribosomes, mitochondria, stacks of annulated lamellae, and “food vacuoles” to the oocytes. Specialized cells which line the tropharium and send projections toward the trophic core have been called “peripheral trophocytes.” Contrary to the regular trophocytes, they contain glycogen and an abundance of Golgi complexes.     

Synthesis of 5 S and transfer RNA during embryogenesis in the milkweed bug, Oncopeltus fasciatus

Synthesis of 5 S RNA and transfer RNA has been shown to begin at the onset of gastrulation in eggs of the milkweed bug, Oncopeltus fasciatus. 5 S RNA synthesis parallels that of ribosomal RNA, but transfer RNA synthesis is somewhat different.     

Differential infectivity of two Pseudomonas species and the immune response in the milkweed bug, Oncopeltus fasciatus (Insecta: Hemiptera).

Pseudomonas aeruginosa and Pseudomonas putida show a profound differential infectivity after inoculation in Oncopeltus fasciatus. Whereas P. putida has no significant impact on nymphs, P. aeruginosa kills all experimental animals within 48 h. Both Pseudomonas species, however, induce the same four hemolymph peptides in O. fasciatus. Also injection of saline solution and injury induced these peptides. In general peptide induction was stronger in nymphs than in adult males. A significantly higher number of nymphs survived a challenge with P. aeruginosa when an immunization with P. putida preceded. The antibacterial properties of the hemolymph were demonstrated in inhibition experiments with P. putida. Two of the four inducible peptides (peptides 1 and 4) could be partially sequenced after Edman degradation and were compared with known antibacterial peptides. Peptide 1, of 15 kDa, showed 47.1% identity with the glycine-rich hemiptericin of Pyrrhocoris apterus. Peptide 4, of 2 kDa, had a 77.8% identity with the proline-rich pyrrhocoricin of P. apterus and a 76.9% identity with metalnikowin 1 of Palomena prasina. Peptides 2 and 3 are also small, with molecular weights of 8 and 5 kDa.     

Male influence on the duration of reproductive diapause in the large milkweed bug, Oncopeltus fasciatus

ABSTRACT. Differences were found in duration of diapause, as measured by days to first oviposition following adult eclosion, between female Oncopeltus fasciatus (Dallas) mated with male O.sandarachatus (Say) (mean =55 days), and those mated with their brothers (mean =99 days). Under the same conditions (LD 11:13 at 23°C), O.sandarachatus pairs showed no delay in reproduction (mean = 12 days). Male O.sandarachatus exhibit greater sexual activity than male O.fasciatus , and it is postulated that this behaviour may play a significant role in determining the length of diapause in the female.     

Carbohydrases in the alimentary canal of the large milkweed bug, Oncopeltus fasciatus (Hemiptera: Lygaeidae)

Adults of the large milkweed bug, oncopeltus fasciatus (Dallas), deprived of food for 48 hr, were fed 5% solutions of either sucrose, maltose, lactose, raffinose or melezitose, for 15–20 min. The alimentary canals were then dissected out 30 min or 1 hour after the period of feeding, and the gut contents chromatographed. The results indicated the presence in the gut of the following carbohydrases: -glucosidase, -fructosidase, -galactosidase and -galactosidase.

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Résumé Des adultes de la punaise de l'asclépiade, Oncopeltus fasciatus (Dallas), soumis au jeûne pendant 48 heures, ont été nourris ensuite durant 15 à 20 minutes avec des solutions aqueuses de 5% de glucides, comprenant soit le sucrose le maltose, le lactose, le raffinose ou le mélézitose. Les tubes digestifs furent prélevés 30 ou 60 minutes après l'ingestion des sucres, et leur contenu glucidique séparé et identifié par chromatographie sur papier filtre. Les résultats ont révélé la présence dans le tube digestif des carbohydrases suivantes: -glucosidase, -fructosidase, -galactosidase et -galactosidase.