Initiation Of Oviposition Research Articles

Autogenic capacity in Triatoma infestans (Klug, 1834) (Hemiptera: Reduviidae) susceptible and resistant to deltamethrin.

The insecticide resistance in Triatoma infestans (Klug, 1834) was detected in different areas of its geographical distribution. The mechanisms of resistance involved can affect different biological processes in addition to toxicological ones. Previous studies showed that reproductive efficiency was modified in resistant females compared to susceptible ones. The objective of this study was to compare the autogenic capacity and subsequent reproductive potential between deltamethrin-resistant and susceptible T. infestans. For each toxicological phenotype, pairs were formed between unfed adult females and recently fed adult male, which were separated after confirming copulation. Females were observed weekly until death, and reproductive parameters (initiation of mating, initiation of oviposition, fecundity, fertility and period between mating and initiation of oviposition) were recorded. Females from both toxicological phenotypes showed autogenic capacity. However, a lower proportion of deltamethrin-resistant unfed females laid eggs. Autogenic females showed a higher nutritional status than non-autogenic ones. No other differences in reproductive parameters were found between resistant and susceptible autogenic females. The possible mechanisms underlying the differences observed and their consequences on the spread of resistance are discussed. This is the first report describing the effect of pyrethroid resistance on T. infestans autogeny.

Onset of Oviposition Triggers Abrupt Reduction in Migratory Flight Behavior and Flight Muscle in the Female Beet Webworm, Loxostege sticticalis.

Flight and reproduction are usually considered as two life history traits that compete for resources in a migratory insect. The beet webworm, Loxostege sticticalis L., manages the costs of migratory flight and reproduction through a trade-off in timing of these two life history traits, where migratory behavior occurs during the preoviposition period. To gain insight into how migratory flight and reproduction are coordinated in the female beet webworm, we conducted experiments beginning at the end of the preoviposition period. We used flight mills to test whether flight performance and supportive flight musculature and fuel are affected by the number of eggs oviposited, or by the age of mated and unmated females after onset of oviposition by the former. The results showed that flight distance, flight velocity, flight duration, and flight muscle mass decreased abruptly at the onset of oviposition, compared to that of virgin females of the same age which did not change over the next 7 d. These results indicate that onset of oviposition triggers a decrease in flight performance and capacity in female beet webworms, as a way of actively managing reallocation of resources away from migratory flight and into egg production. In addition to the abrupt switch, there was a gradual, linear decline in flight performance, flight muscle mass, and flight fuel relative to the number of eggs oviposited. The histolysis of flight muscle and decrease of triglyceride content indicate a progressive degradation in the ability of adults to perform additional migratory flights after onset of oviposition. Although the results show that substantial, albeit reduced, long-duration flights remain possible after oviposition begins, additional long-distance migratory flights probably are not launched after the initiation of oviposition.

Mortality And Reproductive Dynamics of Aedes aegypti (Diptera: Culicidae) Fed Human Blood

Mortality is a critical factor in determining a mosquito's ability to transmit pathogens. We investigated the effect of human blood feeding and reproduction on mortality of the dengue virus vector, Aedes aegypti, by conducting a life-table study of male and female mosquitoes maintained on one of three diets: 10% sucrose, human blood or human blood plus 10% sucrose. We examined the effect of host availability by offering human blood to mosquitoes every day or every other day. Mortality of females was age-dependent and best fit by a logistic or logistic-Makeham model. The availability of blood increased survival; survival of females fed blood plus sugar was greater than those only fed sugar. There was a peak in mortality of females fed blood alone early in life that coincided with the initiation of oviposition. When females in the blood alone group were offered blood daily, their mortality was significantly lower than when they were offered blood every other day. Unlike some previous studies, females fed blood plus sugar had higher fitness than females fed blood alone. Increased fitness may have been due to differences in housing mosquitoes individually in separate cages versus as a group of many mosquitoes in each cage. It was not due to longer survival of males who had access to sugar as a food source. Our results demonstrate that reproductively active Ae. aegypti exhibit age-dependent mortality, which refutes the assumption of age-independent mosquito mortality and underscores the need to incorporate age-dependent factors into pathogen transmission models and research on mosquito biology in general.

Seasonal phenology of Bactrocera minax (Diptera: Tephritidae) in western Bhutan.

The Chinese citrus fruit fly, Bactrocera (Tetradacus) minax (Enderlein), is one of the major citrus pests in Bhutan and can cause >50% mandarin (Citrus reticulata Blanco) fruit drop. As part of the development of a management strategy for the fly in mandarin orchards, population monitoring and experimental manipulations were carried out to determine: (i) adult emergence period; (ii) adult phenology patterns; (iii) period of crop susceptibility; and (iv) period from fruit drop to pupation. In western Bhutan, adult flies emerge from the overwintering pupal stage in late April/early May. Most flies are mature by the end of May and it is inferred that mating occurs at this time: from the beginning of June males rapidly disappear from the population and by mid- to late June are rare or absent from traps. Mature females are present in the mandarin crop at the beginning of June, but very little oviposition occurs until mid-June, while most damage has occurred by mid-July. Initiation of oviposition into mandarins is almost certainly linked to crop phenology. Adult flies disappear from the orchard system during August. After fruit drop, larvae were recorded leaving the fruit to pupate within 13 days. The use of early to mid-season protein bait sprays and/or targeted use of systemic insecticides during the one month oviposition period, plus the removal of fallen fruit once every 10 days, are recommended as control strategies.

Enhanced oviposition in the moth, Plodia interpunctella, after treatment with aminergic analogues

In many species of moths, including Plodia interpunctella, post-mating events include the cessation of sex pheromone communication and the initiation of oviposition. In a previous study we have shown that octopamine and several analogues inhibit the production of sex pheromone in the moth. The present study demonstrates that octopamine and two analogues, clonidine and 2-(2,6-dimethylanilino) imidazolidine induce oviposition by virgin females of P. interpunctella, to a comparable level to that of mated females. Moreover, octopamine caused a significant reduction in the percentage of fertile eggs laid by mated females. It is suggested that octopamine therefore, mimics both the responses that occur post-mating: suppression of sex pheromone biosynthesis and stimulation of oviposition.

Inhibition of pheromone biosynthesis in Helicoverpa armigera by pheromonostatic peptides

Male insect accessory glands contain factors that are transferred during mating to the female, some inducing post-mating behavior, including the cessation of pheromone production, non-receptivity and the initiation of oviposition. One such factor is the Drosophila melanogaster sex-peptide (DrmSP). A pheromone suppression peptide, termed HezPSP, was identified in the moth Helicoverpa zea, isolated by HPLC and the active peak sequenced, but the activity of the synthesized peptide has not been reported to date. HezPSP bears no sequence homology to DrmSP. However, both peptides contain a disulfide bridge separated by an equal number, but dissimilar, amino acids. We herein report on the pheromonostatic activity of HezPSP partial peptides in the moth Helicoverpa armigera.

Phenological Synchrony ofEustenopus villosus(Coleoptera: Curculionidae) withCentaurea solstitialisin Idaho

The phenological synchrony of Eustenopus villosus (Boheman) with its host, yellow starthistle, Centaurea solstitialis L. (Asteraceae: Cardueae), was studied in Idaho in 1995 and 1996. Field plots were observed for adult weevil activity periodically throughout the growing season, and yellow starthistle capitula were examined for adult feeding damage, oviposition damage, and larval development. At the study site, weevil phenology was well synchronized with C. solstitialis. Immature capitula, fed upon by adults, were abundant when E. villosus began to emerge in late May. During both years, the number of weevils and capitula increased throughout June. Adult females fed on capitula for about 2 wk. Weevil ovary dissections revealed that ovaries were mature after a 2-wk period of feeding. The development of mature capitula during late July corresponded to the initiation of oviposition. Eustenopus villosus, unique among the phytophages introduced for C. solstitialis biological control, attacks four plant stages resulting in observable impact to buds. Damaged buds either died or became distorted. Weevil feeding damage on young and mature capitula may make this insect a highly effective control agent.

Prolonged Storage of Chrysoperla carnea (Neuroptera: Chrysopidae)

Diapausing adults of Chrysoperla carnea Stephens were stored at low temperature (5°C) under short daylengths (10:14 [L:D] h) for 31 wk with little maintenance. Rates of survival were very high (≈97%), and both males and females retained high reproductive potential. Shortly after transfer to warm, long-day conditions, >90% of the pairs produced fertile eggs: initiation of oviposition after storage was synchronous and predictable. Subsequently, depending on the duration of storage, females oviposited an average of 230–350 eggs during the first 30 d of oviposition (≈50–70% of the eggs produced by unstored females). Except for one group that was stored for 31 wk, high levels of fertile oviposition persisted for ≈45 d after storage. Cold storage of C. carnea benefits biological control efforts by providing flexibility and efficiency in mass-production to meet peak seasonal demands for eggs or young larvae; an alternative method of shipping C. carnea to distributors who choose to harvest eggs (or young larvae) for sale; and a reserve supply of stock if insectary colonies fail or dwindle. It also makes standardized stock available for use in long-term ecological, physiological, or genetic research.

The duration of strong mate-guarding by males of the libellulid dragonflyPaltothemis lineatipes: Proximate causation

Males of the territorial libellulid dragonfly Paltothemis lineatipeschange the intensity with which they guard their mates during an oviposition bout. Immediately after copulation is completed, males exhibit strong guarding, remaining very close to their partners as they begin ovipositing. In less than a minute, however, they begin to drift away to resume territorial patrolling or even to perch while their partners continue to oviposit. The duration of strong guarding is not related to how long the male has been on territory. Nor is it an activity of fixed duration set by the release of the female following copulation or by the initiation of oviposition by a panner. Instead, males can extend the period of strong guarding if oviposition is interrupted experimentally early in a bout. Under these conditions, males follow their mates closely until they have found a new location at which they oviposit steadily. Thus, males apparently must see their panner oviposit for some time before reducing the intensity of mate-guarding.

Mated-like behaviour in senescent virgin females of gypsy moth, Lymantria dispar

After mating, females of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae) stop producing sex pheromone, become sexually non-receptive, and commence oviposition. These post-mating behaviours were observed to occur spontaneously in senescent virgin females. Strong correlation was shown betweer decrease in sex pheromone, initiation of oviposition and loss of sexual receptivity in ageing virgin females. Thus, the mechanism which induces the change from virgin to mated behaviour appears to reside within the female, although it would be normally triggered in younger females by signals associated with mating. Removal of the spermatheca or bursa copulatrix from virgin females did not prevent the appearance of mated-like behaviour as the females aged.

Distribution of Threecornered Alfalfa Hopper (Homoptera: Membracidae) Eggs in Vegetative Stage Soybean

A2-yr study of the early season distribution of egg clusters of the threecornered alfalfa hopper, Spissistilus festinus , (Say), was conducted in Louisiana soybean fields. The spatial distribution of egg clusters indicated that colonizing S. festinus females disperse throughout the fieldbefore initiation of oviposition. The frequency distribution of egg clusters within a field was best described by the negative binomial (clumped); however, egg clusters were distributed independently among plants within a row. The distribution of egg clusters indicated that females move short distances between ovipositions rather than ovipositing on the same or adjacent plants. Vertical distribution of egg clusters over time showed that the location of preferred oviposition sites shifted upward with plant growth. A parasitoid of threecornered alfalfa hopper eggs was collected and identified as polynema sp.

Effect of Low Holding Temperature During Pupal Instar on Adult Emergence, Pre-Oviposition and Fecundity of Cryptolaemus montrouzieri Mulsant (Coccinellidae: Coleoptera)

The effect of exposing 1, 3 and 5 days old pupae to 10°C for periods of 7, 14, 21 and 28 days on the emergence, pre-oviposition and fecundity of Cryptolaemus montrouzieri Mulsant was studied. The emergence was delayed significantly when 1 and 3 days old pupae were subjected to 10°C for 28 days when compared to 5 days old pupae. The initiation of oviposition was delayed with the prolongation of holding time. The fecundity of females emerging from 5 days old pupae subjected to 10°C for 21 days was found to be significantly higher than in any other treatment.

REPRODUCTIVE CYCLES OF THE RED TURNIP BEETLE, ENTOMOSCELIS AMERICANA BROWN (COLEOPTERA: CHRYSOMELIDAE)

AbstractThe reproductive cycles of the red turnip beetle, Entomoscelis americana Brown, were studied in the field in Manitoba from 1974 to 1978. Vitellogenesis is initiated within the first 3 days after emergence from aestivation in early August. Oviposition begins soon after the first eggs are developed, usually within the first 8 days after emergence. The rate of egg laying reaches a peak within 2 weeks after the initiation of oviposition and then declines gradually during the remainder of the oviposition period. Almost all eggs were laid between mid-August and mid-October. The average numbers of eggs laid per mated female in three oviposition studies were as follows: 1 female per cage (1974), 254±74 (±SE) (range, 11–696); 1 female per cage (1976), 273±47 (range, 0–622); and 25 females per cage (1974), 426±3 (range, 392–462). The most eggs were laid at the lowest temperature regime tested (6–20°C; mean, 12°C). Copulation is initiated in males and females during the 1st day after emergence from aestivation and both mate many times. Stimuli associated with copulation and (or) insemination enhance egg output, but are not required for the initiation of vitellogenesis and oviposition. Males transfer sufficient spermatozoa to the females during the first one or more copulations that occur during the first 8 days after emergence to fertilize almost all eggs produced. A system for classifying the stages of oocyte development is described.

Newer trends in the biosystematics of Membracidae

Membracids, in general, display a very few morphological characters of taxonomic value. Many species exhibit remarkable intraspecific variations, in addition to sexual dimorphism and cornuate polymorphism that makes it difficult to allocate them to their respective taxa, unless a long series of male and female individuals belonging to the same population are available for examination. The male genitalia, although of value in the diagnosis of higher categories of the Membracidae, find limited application at the species level. The nymphal characters, especially those of the fifth immature stage, are very useful in the identification of the species, but nymphal materials are not available except for a few species, and the host plants of many species remain unknown. In recent years, it has become imperative to consider the ecophysiological aspects of these insects for a better and precise understanding of their systematics. The host plant specificity of some species of membracids, the mutual association of a particular species of membracids with a particular species of ants and the parasite-host interaction involving certain chalcidoid egg parasites of membracids are considered with a view to evaluate their role in the membracid taxonomy. The impact of differential reproductive potential in terms of host diversity, the allochronic differences in mating and initiation of oviposition, and the differences in the relative growth patterns with particular reference to the polymorphic speciesOxyrhachis tarandus (Fabricius) on 5 species is investigated.

Numbers of Spermatozoa in Spermathecae of Queens Aged 0 to 3 Years Reared in Beaverlodge, Alberta

SummaryQueen honeybees (Apis mellifera) were reared under optimal conditions between 1982 and 1985. Mean weight of queens at emergence was 213 ± 2·02 mg. At initiation of oviposition (designated 0 years) and after 1, 2 and 3 years in honey-producing colonies, mean numbers of spermatozoa in spermathecae were 9·77 ± 0·79, 7·63 ± 0·85, 5·57 ± 07middot;64 and 2·8 ± 07middot;62 million, respectively; numbers declined logarithmically with age of the queen. Annual requeening of colonies may be unnecessary, if efforts are made to produce queens of the highest quality.

Effects of Honeybee Queen Weight and Air Temperature on the Initiation of Oviposition

SummaryThe onset of oviposition of 1396 queens reared in two years in the Peace River region of Alberta, Canada, ranged from 4 to 22 days after emergence, with a mean of 10·6 ± 0·1 days. There was evidence to suggest that some queens may start to lay eggs within 24 h after mating. No consistent correlation was found between queen weight at emergence and the onset of oviposition. Mean weight of queens was 211·2 ± 0·7 mg (range 160–266 mg) in 1981 and 222·6 ± 0·06 mg (range 173–273 mg) in 1982. There was a close association between maximum daily temperature and time of oviposition. A large number of queens mated at temperatures below 25°C.

Reproductive performance and mutagenic response of the wasp Bracon hebetor following treatment with the antibiotic bleomycin

Bleomycin (BM) induced dominant-lethal genetic lesions in the gametes of both sexes of adult Bracon hebetor wasps following ingestion. This effect was demonstrated by decreased fertility in the unfertilized eggs of treated females as well as in eggs fertilized by mature sperm derived from treated males. Death in the unhatched eggs occurred prior to blastoderm formation indicating BM caused chromosome breakage. Affected ovarian cells were limited to those exposed to BM between the developmental stages of vitellogenesis and early metaphase I. Sperm-associated fertility reductions were temporary in duration with substantial reductions being observed starting on the second day following the initiation of oviposition. BM lowered general egg-formation capacity in treated females but, unlike the fertility effects, decreased fecundity was caused by somatic debility. Although the BM-induced genetic damage observed in B. hebetor was radiomimetic in nature, the time of appearance and duration of the effects did not correspond with previous patterns found when B. hebetor adults were exposed to X-rays. While the differences could be due to the BM detoxification or the repair of BM-induced chromosome damage, further investigation would be required to demonstrate the presence of such systems in this hymemopteran.

Parasitism of Ips sexdentatus (Insecta: Scolytidae) by Parasitorhabditis ipsophila (Nematoda: Rhabditidae)

The study of parasitism percentages and contaminations intensity in Ips sexdentatus parasitized by P. ipsophila as well as the examination of the wormholes in the galleries of the bark beetle gave better insight into certain features of nematode biology. Larvae of I. sexdentatus could be infected, whereas pupae could not. Adults were contaminated from initial stages of maturation and throughout preswarming maturation. Following swarming and installation on a new tree, insects were rapidly decontaminated, but recontamination could occur by the end of oviposition. P. ipsophila larvae were found in the mesenteron before they penetrated into the hind gut. Seemingly, the parasite underwent no evolution within its host. All developmental stages of the nematode could be observed in the galleries of the bark beetle as long as the latter was present. No apparent relation exists between parasitism of the digestive tract by P. ipsophila and parasitism of the body or fat body by Parasitaphelenchus or Contortylenchus diplogaster. P. ipsophila exerts very limited effects on I. sexdentatus populations. A slight delay in swarming and initiation of oviposition, and a very low decrease in density of notches of oviposition and of eggs was observed, but the features of the gallery of oviposition (total length, length before the first notch) showed no alteration. No mortality was detected.

Effects of Insemination on the Initiation of Oviposition in the Queen Honeybee

SummaryThe number of days from emergence to the onset of oviposition in 7 groups of queens was as follows: naturally mated queens, 10·33 ± 0·68; free-flying queens treated with CO2, 11·00 ± 0·36; queens instrumentally inseminated by the Mackensen technique, 13·8 ± 1·94; virgin queens treated with CO2, 14·00 ± 0·77; queens instrumentally inseminated, using the washing technique, 14·58 ± 0·53; queens injected with washing fluid, 15·82 ± 1·42; queens injected with Kiev solution, 17·77 ± 1·24. The number of spermatozoa in the spermatheca of naturally mated queens, of queens inseminated by the Mackensen technique, and of queens inseminated by the washing technique, was 4·54 ± 0·7, 3·83 ± 0·47, and 3·02 ± 0·52 millions, respectively. Naturally mated queens started laying eggs earlier than the instrumentally inseminated queens.

The Interaction of Xyleborus ferrugineus (Coleoptera: Scolytidae) Behavior and Initial Reproduction in Relation to Its Symbiotic Fungi1

Females of the ambrosia beetle Xyleborus ferrugineus were reared on diets with and without symbiotic fungi. Daily observations were made for overall activity level, major types of behavior, length of tunneling, and ovipositions. On both fungus-containing and non-fungus diets overall activity level was significantly greater for days 4-9 than for days 1-3 on diet. Females on fungus diet switched their dominant behavior from burrowing/removing during pre-oviposition to feeding/cleaning during post-oviposition; on non-fungus diet no such switch was observed. Mean tunnel length by day 8 was significantly greater for females on non-fungus diet than those on fungus diet. The day of 1st oviposition was significantly earlier for females on fungus diet than for those on non-fungus diet. These differences suggest that some nutritional threshold is involved in allowing initiation of oviposition.