Role of juvenile hormone in the synthesis and sequestration of vitellogenins in the red cotton stainer, Dysdercus koenigii (Heteroptera: Pyrrhocoridae)

Investigations were carried out to determine the role of juvenile hormone (JH) and 20-hydroxy ecdysone in the synthesis and uptake of vitellogenins, which were earlier identified, purified and characterised, in Dysdercus koenigii. The concentration(s) of vitellogenin(s) in fat body, haemolymph and that of vitellin(s) in ovary were significantly lower after chemical allatectomy at eclosion. In addition, at 70 h after emergence, chemical allatectomy reduced ovarian vitellin concentration, but vitellogenin levels remained normal in the fat body and haemolymph. The haemolymph vitellogenins were not incorporated into oocytes in such insects. Administration of JH-III at 20 h after allatectomy restored vitellogenin levels in the fat body and haemolymph, but the ovary failed to incorporate the available vitellogenins from haemolymph in such insects. However, when JH-III was administered twice, one at 20 h and then at 70 h after allatectomy, vitellogenin concentrations in fat body and haemolymph and also vitellin concentrations in ovary approached control levels. It is suggested that JH has two separate roles, one in vitellogenin synthesis and the other in uptake. 20-hydroxy ecdysone had no apparent role in either vitellogenin synthesis or uptake in D. koenigii.     

Effect of actinomycin-D on the fat body RNA content in Dysdercus koenigii (Heteroptera: Pyrrhocoridae)

The effect of actinomycin-D on the RNA content of the total fat body was studied on day 3, 4, 5 and 6 of the first reproductive cycle in the females. Actinomycin-D exhibited its highest inhibitory effect in insects injected on day 4 and a lower degree of the effect was seen in insects injected on day 5. These results suggest that by the end of day 4, a major quantity of DNA-dependent RNA, necessary for vitellogenin synthesis, has already been synthesised and accumulated.     

The exocrine glands of Dysdercus cingulatus (Heteroptera,Pyrrhocoridae): Morphology and function of nymphal glands

The exocrine glandular system of the nymphs and the adults of Dysdercus cingulatus were studied. The D. cingulatus nymphs present 3 dorso-abdominal glands (lying under the 3rd, 4th, and 5th abdominal terga) and a pair of dorso-lateral pygidial glands on the pygidium (tergum 8). Histological and ultrastructural studies show that the upper and lower walls of the dorso-abdominal glands differ in structure; 3 types of cells were described: epidermal cells, unicellular secretory cells, and multicellular secretory units. Each of these exocrine glands plays an important part in the behavior of the nymphs (gregariousness, alarm, defense). The morphology of the various glands is discussed, and the chemistry of their secretions and their biological functions are considered.     

Effect of short-term cold temperature stress on development,survival and reproduction of Dysdercus koenigii (Hemiptera: Pyrrhocoridae)

Red cotton bug Dysdercus koenigii F. (Hemiptera: Pyrrhocoridae), is found destructive pest in various cotton growing areas. Under natural conditions insects are highly subjected to thermal stresses. In present work the developmental duration and survival rate of all immature stages, adult longevity and reproduction of D. koenigii by exposed to rapid changes in very low temperatures were studied. When 3 h short-stress of low temperatures (12–0 °C) was given to different stages of D. koenigii, the results revealed that survival rate of all stages were significantly reduced. Survival rate of female was significantly higher than male after exposed to cold temperature stress. Mating percentage, fecundity and hatching percentage were decreased significantly with the decrease of short-term cold temperature stress. Based on these results, we concluded that the developmental duration, survival rate and reproduction of D. koenigii significantly affected when they exposed to short term cold temperature stress.     

Peculiarities of the epidermal gland system of the cotton stainer Dysdercus fasciatus Signoret (Heteroptera: Pyrrhocoridae)

The epidermal gland system of adult Dysdercus fasciatus, which shows conspicuous sexual dimorphism, is described. Observations on the development of the glands and a discussion of their possible functions are included.     

The larval development of the telotrophic meroistic ovary in the bug Dysdercus intermedius (Heteroptera, Pyrrhocoridae)

Bug ovaries are of the telotrophic meroistic type. Nurse cells are restricted to the anterior tropharium and are in syncytial connection with the oocytes via the acellular trophic core region into which cytoplasmic projections of oocytes and nurse cells open. The origin of intercellular connections in bug ovaries is not well understood. In order to elucidate the cellular processes underlying the emergence of the syncytium, we analysed the development of the ovary of Dysdercus intermedius throughout the five larval instars. Up to the third instar, the germ cell population of an ovariole anlage forms a single, tight rosette. In the center of the rosette, phosphotyrosine containing proteins and f-actin accumulate. This center is filled with fusomal cytoplasm and closely interdigitating cell membranes known as the membrane labyrinth. With the molt to the fourth instar germ cells enhance their mitotic activity considerably. As a rule, germ cells divide asynchronously. Simultaneously, the membrane labyrinth expands and establishes a central column within the growing tropharium. In the fifth instar the membrane labyrinth retracts to an apical position, where it is maintained even in ovarioles of adult females. The former membrane labyrinth in middle and posterior regions of the tropharium is replaced by the central core to which nurse cells and oocytes are syncytially connected. Germ cells in the most anterior part of the tropharium, i.e. those in close proximity to the membrane labyrinth remain proliferative. The posterior-most germ cells enter meiosis and become oocytes. The majority of the ovarioles' germ cells, located in between these two populations, endopolyploidize and function as nurse cells. We conclude that the extensive multiplication of germ cells and their syncytial assembly during larval development is achieved by incomplete cytokineses followed by massive membrane production. Membranes are degraded as soon as the trophic core develops. For comparative reasons, we also undertook a cursory examination of early germ cell development in Dysdercus intermedius males. All results were compatible with the known basic patterns of early insect spermatogenesis. Germ cells run through mitotic and meiotic divisions in synchronous clusters emerging from incomplete cytokineses. During the division phase, the germ cells of an individual cluster are connected by a polyfusome rich in f-actin.     

Effect of Artemisia annua oil on development and reproduction of Dysdercus koenigii F. (Hem., Pyrrhocoridae)

The effect of topical application of Artemisia annua oil on the development and reproduction of Dysdercus koenigii was studied. On the basis of 48 h mortality, the LD₅₀ for fifth instar nymphs was 0.48 μl/nymph. The treated nymphs showed 2 days delay in development, and also produced intermediates. The treatment decreased haemolymph protein concentration and disturbed its electrophoretic protein pattern. The adults which emerged from treated nymphs showed poor ovary development. There was a greater median neurosecretory activity in the treated insects compared with control insects till day 6 of adult life.     

Effects of Ocimum sanctum hexane extract on survival and development of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoriedae)

Abstract

The effects of hexane extract of Ocimum sanctum leaves on the survival, longevity, growth and development of the Dysdercus koenigii Fabricius were investigated. Newly emerged fifth instar nymphs were exposed to nine concentrations ranging from 0.00625% to 10% of the extract for 24?h by “dry film residual method.” The results indicated that the extract has adverse effect on various life activities studied. The effects were dose related; exposure to a dose of 5% or more causes high mortality. Normal adults were not produced from the nymphs treated with extract concentrations of 1.25% or more. The treated nymphs exhibited developmental malformation. The gas chromatography and mass spectroscopy analysis of the extract revealed presence of chemical compounds having insecticidal and juvenile hormone (JH) mimicking activities. Some of the compounds act as precursors of JH biosynthetic pathways. Therefore, these compounds may individually or synergistically can be used in management of D. koenigii and other insect pests.     

Chemosterilant activity of naturally occurring quinones and their analogues in the red cotton bug, Dysdercus koenigii (Het., Pyrrhocoridae)

The chemosterilant activity of two naturally occurring napthaquinones, plumbagin from Plumbago sp. and juglone from Juglans regia has been evaluated using the red cotton bug Dysdercus koenigii . Their activity were compared with synthetic napthaquinones, menadione, two benzoquinones, 2,6-dimethyl and 2,3,6-trimethylbenzoquinone and a hydroquinone 2,6-dimethylhydroquinone. As far as the authors are aware, the present investigation is the first systematic attempt to investigate the effects of quinones on different aspects of reproduction, namely mating behaviour, fecundity and fertility. All the above types of quinones have revealed adverse effects on the reproduction of D. koenigii , which were topically treated as 1-day-old adults with different doses of the compounds depending on their 50% lethality (LD₅₀) values. Analysis of the data revealed a highly statistically significant reduction in the number of eggs, their hatching and further development up to the final instar stage. The sterility index increased with the increase in the dose of any of the above compounds and was highest when both sexes were treated. Among the natural products, juglone induced more sterilizing effects than plumbagin at 5–10  μ g/insect. Menadione caused sterility at a very low dose such as 0.5  μ g. Of the two benzoquinones, the dimethylbenzoquinone acted at a much lower dose.     

Absence of phytosterol dealkylation and identification of the major ecdysteroid as makisterone A in Dysdercus fasciatus (Heteroptera,Pyrrhocoridae)

The absence of phytosterol dealkylation in the cotton stainer bug, Dysdercus fasciatus, has been established and the major ecdysteroid in the fifth-stage larvae identified. The demonstration that the free and esterified sterols in D fasciatus consisted of 95–96% sitosterol and 4–5% campesterol, a similar composition to the cottonseed diet, together with the lack of conversion of [¹⁴C]sitosterol into cholesterol, establishes that phytosterol dealkylation does not occur in this insect species. The ecdysteroid titer determined by radioimmunoassay in the fifth instar of D fasciatus shows a distinct peak at day 6, the instar lasting for 7 days. Makisterone A was purified by HPLC from insects at a time of high ecdysteroid titer and identified as a major component by both fast atom bombardment and electron impact mass spectrometry. Gas-liquid chromatography/mass spectrometry (selected ion monitoring) confirmed the occurrence of makisterone A and revealed the presence of two unidentified compounds. One of these occurs in a similar amount to makisterone A and may be 26-hydroxymakisterone A, whereas only a minute amount of the other compound, which may be 20-deoxymakisterone A, was present; further identification of the latter compounds is necessary. C₂₇ ecdysteroids (eg, ecdysone and 20-hydroxyecdysone) and C₂₉ ecdysteroids (eg, podecdysone A) were undetectable. The specificity of the enzymes of ecdysteroid biosynthesis is discussed.     

Insect growth regulatory activity of naturally occurring quinones and their derivatives in Dysdercus koenigii Fabr. (Hem., Pyrrhocoridae)

Plumbagin, a naphthoquinone occurring in the plants belonging to Plumbago sp. is known to have insect growth disrupting activities. In the present study, a comparative evaluation of bioactivities of related naphthoquinones, juglone and menadione and benzoquinones, 2,6-dimethylbenzoquinone and 2,3,6-trimethylbenzoquinone along with 2,6-dimethylhydroquinone have been undertaken using Dysdercus koenigii . The LD₅₀ values of the compounds showed wide variation. Although all the test compounds disrupted the normal growth at sublethal doses, 2,6-dimethylbenzoquinone and menadione showed activity at low doses.     

Effects of hexane extract of Lantana camara leaves on reproductive bioactivities of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoreidae)

Effects of hexane extract of Lantana camara leaves were investigated on reproductive bioactivities of Dysdercus koenigii by assessing mating behavior, oviposition behavior and fertility of the adults emerged from treated fifth instar nymphs. Leaves of L. camara were extracted in hexane by ‘cold extraction method’. The fifth instar nymphs were treated with the extract by ‘dry film residual method’ for 24 h and the adults emerged from these nymphs were used for the experiments. The results indicated that treated males showed altered courtship behaviour, lesser number of mounting attempts and took relatively more time to mate than the normal males. The treated females, very often, exhibited mating refusal and non-receptive behaviour towards the courting males. This led to decrease in percent successful mating. Also, the mating in the treated insects frequently got disrupted and terminated prior to insemination. The treatment of the females with the extract resulted in alteration of their oviposition behaviour. Consequently, the treated females laid lesser number of egg batches and total number of eggs in their life span. Although the eggs laid by the treated females were fertile, the percent hatchability was lesser than normal. The results signify that hexane leaf extract of L. camara possesses phytochemicals, which adversely impaired the reproductive bioactivities of D. koenigii. Therefore, some of these compounds individually or synergistically can be employed in integrated pest management of D. koenigii by hampering its reproductive potential.     

Evolution of mimicry in the New World Dysdercus (Hemiptera: Pyrrhocoridae)

Evolution of mimicry rings is reconstructed for the New World species of cotton-stainer bugs (Dysdercus, Hemiptera: Pyrrhocoridae). Using a cladistic analysis of 43 species (including D. silaceus Doesburg, 1968 stat. nov . and D. modestus Doesburg, 1968 stat. nov .), evolution of colour patterns and biogeographical history of the clade are hypothesized. Three probable mimicry rings are obtained from the analysis, together with data about their possible model–mimic or comimic–comimic structures: (a) ‘Yellow’ species in north-western South America and in the Andes (several possible models, D. rusticus, D. mimus part., D. imitator part., and D. collaris part. as mimics); (b) ‘Median Yellow–Black’ species with a median-forewing black pattern in north-western South America and Central America (several possible models, D. basialbus as a mimic); (c) ‘Median Red–Black’ species with a median-forewing black pattern in the Caribbean islands (D. andreae, D. discolor, D. neglectus–D. sanguinarius clade, and D. jamaicensis–D. fervidus–D. ocreatus clade as comimics). A few additional, less supported rings are also identified. Two highly polymorphic species (D. obscuratus, D. mimus) seem to enter different mimicry rings in different regions.     

Size and Partner Choice in Dysdercus maurus Distant (Hemiptera: Pyrrhocoridae)

This study investigates whether females of Dysdercus maurus (Hemiptera) are considering male’s sizes in order to make their reproductive partner choice. Morphometric and biomass measurements were obtained from single males and copulating pairs. Positive correlations were identified for both sizes and weights between males and females in copula. The average ratios established between the couples sizes/weight were around 1.66. Female choice may operate in such a way that each female has her own optimal male size for mating, resulting from a trade-off between the negative influence of large partner size in female fecundity and the advantages of large male size for offspring fitness. Thus, the best choice for a D. maurus female may be a male of average size in relation with her own size.     

Repetitive mating and female fitness in Dysdercus cardinalis (Hemiptera: Pyrrhocoridae)

Using three mating-treatment groups–pairing with a male for life, pairing with a male from adult emergence to first oviposition, and no pairing (virgin)–of Dysdercus cardinalis females in a laboratory study, the following results were obtained. Most of the virgin females did not lay eggs; those that did oviposited for the first time at a considerably older age than females in the other two groups. In a lifetime, females pairing with a male for life and those pairing with a male up to first oviposition produced essentially the same number of eggs, and this was more than 3.5 times the number of eggs laid by a virgin female. Virgin females produced an average of 1.3 clutches in a lifetime, compared with about 4.5 clutches produced by females in the other two groups. Reproductive span was significantly shorter, and fecundity per day of reproductive span significantly greater, for females pairing with males for life than for those pairing with a male up to first oviposition. Age at death was significantly different amongst females in different mating-treatment groups. Virgin females had the longest life, followed by females pairing with a male up to first oviposition and females pairing with a male for life, in that order. There was a positive correlation between lifetime gross reproduction and age at death for females pairing with a male for life. There was no relationship between these two characters for females pairing with a male up to first oviposition. Both females pairing with a male for life and those pairing with a male to first oviposition exhibited a significant inverse relationship between fecundity per day and age at death. The results obtained indicate that (1) mating is a prerequisite for normal gonadal activity in Dysdercus cardinalis , and (2) repetitive mating increases the rate of reproduction. This would reduce the mean age of parenthood which is inversely related to the intrinsic rate of increase.     

Body size, symmetry and courtship behavior of Dysdercus maurus Distant (Hemiptera: Pyrrhocoridae)

This study analyses the role of body size and symmetry in the sexual selection and courtship behavior of Dysdercus maurus Distant. Sexual conflicts signaled by coercive mating, female resistance, and pre-copulation fights illustrate the mating system. Male-female struggles were observed in all mating attempts. Females tried to reject males by pushing or running and even by vigorously shaking their bodies, in attempts to dislodge the male from their dorsum. In spite of sexual conflicts during courtship, females actively chose their mates based on morphological and behavioral traits. Larger males with more symmetrical tibiae and longer tarsi that are better copula imposers were more successful in sexual competition. Evidence is presented that sexual conflict and female mate choice should not be mutually excluded.     

Body Colouration Related to the Deposition of Pteridines in the Epidermis and Other Organs of Dysdercus Species (Insecta; Heteroptera: Pyrrhocoridae)

In epidermal cells of Dysdercus species, two types of pigment granules were detected using both light and electron microscopic methods; the granules differed in colour, size, distribution and osmiophily. Red (D. intermedius) and yellow (D. nigrofasciatus) epidermal cells contained both types of granules, but in white cells only one type was present. Chromatographic analyses showed that the larger granules were more transparent to electrons, and contained uric acid, while the smaller ones contained erythropterin, became coloured later, and were osmiophilic. In accordance with these findings, in the testes of D. intermedius both granule types were present, but in the testes of D. nigrofasciatus only those containing erythropterin. The number of granules per cell varied with the species and developmental stage. Epidermal cells of D. intermedius contained more erythropterin granules than those of D. nigrofasciatus, the reverse occurring in the testes. This pattern corresponded to the visible colouration of the insects. As the development progressed, a decrease of the red and an increase of the white granules took place in the coloured epidermal cells. The main amount of pteridines, except isoxanthopterin, was accumulated in the integument of the insects studied. Chemical and histological data showed the influence of pterins on insect colouration. Orange, yellow and red colours were caused by different amounts of erythropterin containing special granules in the epidermal cells, and the white colour only by uric acid containing granules. A partial melanization of the cuticle resulted in dark spots below which pteridines were deposited additionally in the epidermal cells. Considering erythropterin, the quantitative chemical data are in accordance with the histological ones and also with the colouration externally visible. Intensively red coloured stages had a higher concentration of erythropterin and more corresponding granules than the light-red coloured ones; the lowest amount was found in yellow coloured insects. Therefore, the pigmentation effect of erythropterin, which reached from yellow to orange and red, depended on its concentration and played the most important role in the colouration of the Dysdercus species studied, uric acid was responsible for the colouration of the white parts of the integument.     

Ecology of cotton stainers (Heteroptera: Pyrrhocoridae) in southern Ghana

An account is given of the ecology of four species of Dysdercus in southern Ghana. Succession of host plants, host preference and migration is studied. Colony structure is examined. Natural enemies are investigated. Mimetic resemblance of the resident predator to a particular species of host Dysdercus is studied. Experiments on the palatibility of Dysdercus species to mammalian predators are discussed.     

Voltinism and seasonal changes in haemolymph protein pattern of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) in relation to diapause

Abstract. The red firebug, Pyrrhocoris apterus (L.), was shown not to be strictly a monovoltine species in Czechoslovakia. A second generation arises from eggs laid by females emerging between June and the beginning of August. Oviposition takes place before diapause is induced in the females by shortening of photophase. Adults that moult later, enter diapause without having laid eggs.
Electrophoretic patterns of haemolymph proteins of adults collected in the field throughout a year showed a characteristic temporal pattern of changes correlated not only with the stages of ovarian development, but also with the progression of diapause and post-diapause quiescence. The changes mainly concerned vitellogenin and polypeptides of molecular weight 78 and 80 kDa.
Vitellogenin was present only in the haemolymph of reproductive females. The polypeptides of 78 and 80 kDa, belonging to the group of storage proteins, accumulated conspicuously in the haemolymph of adults undergoing diapause and post-diapause quiescence. However, the occurrence of these polypeptides seems not to be connected exclusively with cold, because their titres increased with the length of diapause development, even in diapausing adults reared in the laboratory at a constant 26.C