Circadian rhythm of sex pheromone-releasing behaviour in females of the dermestid beetle,Trogoderma glabrum: Regulation by photoperiod

The effects on sex pheromone-releasing, or calling behaviour, of diel photoperiods of varying daylength, of light cycle phase shifts, and of continuous illumination were investigated in Trogoderma glabrum females. On light régimes with 8 to 20 hr daylengths, calling maxima tended to centre close to photophase midpoints. Although influencing the time of day at which calling occurred, daylength had little effect on the amount of activity or the length of the calling period. When 16 : 8 LD light cycles were advanced or delayed by 4 hr, the time of day at which calling peaks were observed shifted within 2 to 4 cycles so that a constant phase relationship with photoperiod was maintained. Daily calling peaks were evident in groups of females exposed to between 1 and 5 days of continuous illumination, but mean calling time occurred earlier in the day as light exposures were lengthened. It was concluded that a circadian rhythm of calling behaviour exists in T. glabrum females. and that the rhythm can be entrained to 24 hr periodicity by photoperiod.     

Factors influencing the pathogenicity and development of Mattesia trogodermae infecting Trogoderma glabrum larvae

Factors that regulate development of Mattesia trogodermae in Trogoderma glabrum were defined, and their quantitative effects were determined. The rate of and the extent to which spore formation proceeds is strictly governed by temperature. More spores are produced at 30° than at 25°C and very low numbers of spores are formed when the incubation temperature is 35°C. When insects are incubated at 35°C for 1–10 days and transferred to 30°C for the remainder of the 30-day experiment, spore production capacity gradually declines with increasing time at 35°C. Two hypotheses are proposed for this phenomenon. Larval size also regulates the extent of spore production, larger larvae having greater potential for spore development. This is not influenced by dosage. Spore production in pupae and adults was always retarded.Dosage and environmental conditions which influence the virulence of M. trogodermae were investigated. These studies show that rates of mortality are higher at higher temperatures. Low doses of spores result in longer LT50's than do high doses at 25° and 30°C. No differences in rates of mortality were found between different doses at 35°C.     

Physical and physiological characteristics of Trogoderma glabrum infected with the schizogregarine pathogen Mattesia trogodermae

Physical and physiological characteristics of an infection of Trogoderma glabrum by Mattesia trogodermae were studied. Weights of infected larvae drop markedly between 10 and 20 days post-infection at 30° and 35°C. This loss is less abrupt and not as great when the incubation temperature is 25°C. Reduction of dry matter is gradual during the first 12 days of infection, but drops 70% from 12 to 20 days post-infection.Glycogen reserves in both infected and control insects drop 50% within 3 days after deprivation of food. Healthy insects recover and begin to reconstitute lost glycogen; however, infected larvae continue to deplete glycogen to 15% of prestarvation levels. Similarly, insect protein is reduced 40% within 7 days after starvation and noninfected insects apparently halt protein metabolism at this level. Diseased larvae continue to lose protein to 20% of prestarvation amounts. These losses are at least partially attributable to insect metabolism since infected insects defecate significantly more than control larvae. It is thought that defecation is an effective route of water loss which occurs during the first 20 days of infection. Relative humidities ranging from 0 to 84% had no obvious effects on mortality rates, indicating that water loss is effected through routes other than evaporation through the cuticle, e.g., failure of water retention systems and elimination of body water with feces.     

Effects of gamma radiation on the postembryonic stages of a dermestid beetle, Anthrenus vorax waterhouse

The postembryonic stages of Anthrenus vorax proved to be susceptible to doses of 5, 10, 15 and 20 k rad. Pupation was more or less completely inhibited, but some larvae pupated after repeated moults, reduction in size and regrowth, and emerged as normal adults. Percentage of successful moults decreased with increasing doses.At lower doses, more last-stage larvae died in the prepupal stage; at higher doses, larval mortality was higher. Radiation of the early prepupa hampered the pupal moult, that of the late prepupa did not, but produced certain malformations in the adult.In the pupal stage, the later the pupa was radiated, the less susceptible it was, radiation during the first 3 days after pupation being more harmful than later. Pre-emergent adults and pupae of 5 and 6 days old were exposed to different doses of radiation. Data on the fecundity and fertility of various mating combinations of irradiated and non-irradiated males and females are presented and discussed.

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Zusammenfassung Die postembryonalen Stadien von Anthrenus vorax erwiesen sich gegen Strahlendosen von 5, 10, 15 und 20 k rad als empfindlich. Die Verpuppung war mehr oder weniger vollständig gehemmt, jedoch verpuppten sich einige wenige Larven nach wiederholten Häutungen, Größen-rückgang und erneutem Wachstum und schliipften als normale Adulte. Der Prozentsatz erfolgreicher Häutungen verringerte sich mit ansteigenden Dosen.Bei niederen Dosen starben die älteren Larven vor allem im Präpuppenstadium; bei höheren Dosen war ihre Larvensterblichkeit höher. Bestrahlung im frühen Präpuppenstadium hemmte die Puppenhäutung, im späten Puppenstadium dagegen nicht, verursachte dann aber gewisse Mißbildungen bei der Imago.Das Puppenstadium war gegenüber der Bestrahlung um so weniger empfindlich, je später die Puppe bestrahlt wurde. Während der ersten drei Tage nach der Verpuppung wirkte die Bestrahlung schädlicher als danach. Schlüpfreife Käfer und 5–6 Tage alte Puppen wurden verschiedenen Strahlendosen ausgesetzt. Es werden Angaben über Zeugungsfähigkeit und Fruchtbarkeit verschiedener Paarungskombinationen bestrahlter und unbestrahlter Männchen und Weibchen gemacht und besprochen.

     

Homosexual behaviour and its longevity cost in females and males of the seed beetle Acanthoscelides obtectus

The level of homosexual behaviour is evaluated in one laboratory population of seed beetle and derived lines selected to reproduce early (E) or late in life (L), where inadvertent selection for either low or high heterosexual activity has been detected. The magnitudes of homosexual interaction, measured as chasing and mounting individuals of the same sex, are estimated over different age classes. These magnitudes are correlated with previously observed levels and patterns of age‐specific variation of heterosexual activity of both sexes in the E and L experimental lines. The results obtained support the perception error hypothesis proposing that a low degree of sexual discrimination is genetically correlated with high sexual activity. The fitness costs of the same‐sex interactions are tested by assessing their effects on longevity. In both sexes, the longevities of homosexual pairs are reduced relative to individually‐housed virgin beetles in both the E and L lines, although homosexual interactions have a more pronounced effect on male survival than on female survival. Although the results obtained suggest that the longevity cost of homosexual interactions can be substantial, this cost is much smaller than the cost of heterosexual interactions.     

Digestive proteinase activity of the Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae)

The khapra beetle, Trogoderma granarium, is one of the most important stored product pests worldwide. A study of digestive proteinases in T. granarium was performed to identify potential targets for proteinaceous biopesticides, such as proteinase inhibitors. The pH of guts was determined by addition of pH indicator solutions to broken open gut regions. The last instar larvae were dissected in cold distilled water and the whole guts were cleaned from adhering unwanted tissues. The pooled gut homogenates were centrifuged and the supernatants were used in the subsequent enzyme assay. Total proteinases activity of the gut homogenates was determined using the protein substrate azocasein. Optimal azocasein hydrolysis by luminal proteinases of the larvae of T. granarium was highly alkaline in pH 10-10.5, although the pH of luminal contents was slightly acidic (pH 6.5). The extract showed the highest activity at 55 degrees C (pH 6.5), 45 degrees C (pH 8) and 30 degrees C (pH 10). The proteolytic activity was strongly inhibited in the presence of phenylmethylsulphonyl fluoride (82.33+/-4.37% inhibition). This inhibition was decreased with increasing of the pH of assay incubating medium. N-p-tosyl-L-lysine chloromethyl ketone (51.6+/-3.3% inhibition) and N-tosyl-L-phenylalanine chloromethyl ketone (27.23+/-4.37 % inhibition) showed inhibitory effect on proteolysis. Addition of thiol activators dithiothreitol and L-cysteine had not enhanced azocaseinolytic activity. The data suggest that protein digestion in the larvae of T. granarium is primarily dependent on serine proteinases; trypsin- and chymotrypsin-like proteinases.     

Response of the females of Trogoderma granarium (Coleoptera, Dermestidae) to cuticular free fatty acids

Brief extraction of the virgin females of Trogoderma granarium yielded a mixture of fatty acids, the major ones being palmitic and oleic acids; these were accompanied by minor quantities of linoleic, palmitoleic, margaric and stearic acids. The aggregation effect of these cuticular fatty acids on the females of Trogoderma granarium is recorded.

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Résumé Des femelles vierges de Trogoderma granarium sont soumises à une extraction rapide en vue d'obtenir seulement les lipides de la surface cuticulaire. On obtient un mélange d'acides gras dont les plus importants sont les acides palmitique et oléique, accompagnés de petites quantités d'acides linoléique, palmitoléique, margarique et stéarique. Ces divers acidès gras cuticulaires ont un effet attractif plus ou moins marqué sur les femelles de Trogoderma.

     

Mating refusal and its significance in females of the ladybird beetle, Harmonia axyridis

ABSTRACT. . Mating receptivity in females of the ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was studied with reference to internal and environmental conditions. Females sometimes reject copulation: they run away, or shake off the male and bend the abdomen upwards. Newly emerged females show a greater likelihood of accepting copulation with an advance in the stage of ovarian development, this being related to age. Females usually mate repeatedly, but frequently show refusal behaviour under unfavourable food conditions. Dissections reveal that females which accept copulation have a greater number of mature eggs in the ovary than do rejectors. Results also suggest that the food conditions are a major environmental factor, directly controlling mating receptivity.     

The effect of scorpion venom on the moulting activity of larvae of the beetle Trogoderma granarium

Injection of sublethal doses of venom from the scorpion Leiurus quinquestriatus H. et E. into starved diapausing larvae of Trogoderma granarium results in additional larval moults. When the injected larvae were subjected to diapause-terminating conditions (leading to pupation) by transfer to test tubes containing fresh food, the injection of venom sharply decreased the number of pupal moults and increased the number of larval moults.

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Résumé L'injection à des larves en diapause de Trogoderma granarium, de doses subléthales du venin du scorpion Leiurus quinquestriatus, a pour conséquence l'apparition de mues larvaires supplémentaires. Quand des larves sont soumises à des conditions mettant fin à la diapause (aboutissant normalement à la nymphose), par transfert dans des tubes contenant de la nourriture fraîche, l'injection de venin réduit fortement le nombre de mues nymphales et accroît celui des mues. larvaires.

     

Sex allocation and interactions between relatives in the bean beetle, Callosobruchus maculatus

When a small number of females contribute offspring to a discrete mating group, sex allocation (Local Mate Competition: LMC) theory predicts that females should bias their offspring sex ratio towards daughters, which avoids the fitness costs of their sons competing with each other. Conversely, when a large number of females contribute offspring to a patch, they are expected to invest equally in sons and daughters. Furthermore, sex ratios of species that regularly experience variable foundress numbers are closer to those predicted by LMC theory than species that encounter less variable foundress number scenarios. Due to their patterns of resource use, female Callosobruchus maculatus are likely to experience a broad range of foundress number scenarios. We carried out three experiments to test whether female C. maculatus adjust their sex ratios in response to foundress number and two other indicators of LMC: ovipositing on pre-parasitised patches and ovipositing with sisters. We did not find any evidence of the predicted sex ratio adjustment, but we did find evidence of kin biased behaviour.     

雌性延迟发育的蚜虫的性别分配

某些物种的蚜虫中,雌性个体成熟较晚,可以认为是雄性个体的“侄女”。当冬季即将来临,剩余时间就不能满足发育需求时,发育延迟了,发育延迟应当也终止了雌性功能上的投资。然而,最近的证明表明,雌性功能的投资并不停止。这种未预料到的发现可能归因于一种进化限制因素,归因于雄性个体在不同年龄阶段对配偶的竞争,或归因于不能预测导致随机非遗传多型性的最后期限。本文讨论了这三种可能性,最后一种可能性由于暂时性地解释了雌性功能中的连续投资而是一种可取的解释。尽管延缓发育和开始繁殖的最后期限常见于那些生活在严寒地区的、雌性发育迟缓的蚜虫,本文的观点也适合于一个性别成熟较晚的、具有繁殖最后期限的任何一个蚜虫物种。     

Mate discrimination by females in the burying beetle Nicrophorus orbicollis: the influence of male size on attractiveness to females

1. Female burying beetles behave differently towards males of different sizes, avoiding mating with large males that are not defending resources but mating with small males regardless of the presence of resources. Females of the burying beetle Nicrophorus orbicollis were therefore examined to determine whether they discriminate among males using only pheromonal signals. The influence of female size on its own mate choice was also examined. 2. Females do use male pheromonal signals to discriminate among males and these signals do appear to convey information about male body size to females. Overall, females were more likely to be attracted to larger males than to smaller males. 3. Female choice of a male was influenced by both the female's own body size and the size of the female relative to the size of the two males available to it. 4. While there is an overall mating advantage for larger males, resulting from female preferences based on odour cues, smaller males are also attractive to some females under some circumstances. 5. It is argued that there are different costs and benefits of mating with different sized males, leading to the evolution of context‐dependent mate choice for females and the need to be able to discriminate males of different sizes from a distance.     

Avoidance of reproductive interference causes resource partitioning in bean beetle females

Reproductive interference is any interspecific sexual interaction that adversely affects female fitness through indiscriminate reproductive activities. It can be a driving force of resource partitioning in conjunction with resource competition. We previously showed that the bean beetle Callosobruchus maculatus is superior in larval resource competition, but vulnerable in reproductive interference, compared with its congener C. chinensis. We hypothesized that these two species might use two resources differently if one of the resources modified the intensity of reproductive interference or resource competition. We observed that C. maculatus females often enter gaps between beans to avoid mating attempts of heterospecific males, and hypothesized that removing bean gaps would strengthen reproductive interference. Therefore, we provided normal beans with gaps and split beans without gaps to females of the two species housed with conspecific or heterospecific males or no males and compared the number of eggs on each bean type among treatments. Callosobruchus maculatus females housed with heterospecific males were more likely to oviposit on normal beans than C. chinensis females. As a result, more C. chinensis adults hatched from split beans and more C. maculatus hatched from normal beans when females and males of both species were housed together. Thus, oviposition resource partitioning resulted from the combination of female avoidance of reproductive interference and resource competition.