Impact of mating status on egg-laying and superparasitism behaviour in a parasitoid wasp

Most parasitoid female wasps can distinguish between unparasitized and parasitized hosts and use this information to optimize their progeny and sex allocation. In this study, we explored the impact of mating on oviposition behaviour (parasitism and self‐ and conspecific superparasitism) on both unparasitized and already parasitized hosts in the solitary parasitoid wasp Eupelmus vuilleti (Crw.) (Hymenoptera: Eupelmidae). Virgin and mated females had the same oviposition behaviour and laid eggs preferentially on unparasitized hosts. The sex ratio (as the proportion of females) of eggs laid by mated females in parasitism and conspecific superparasitism was 0.67 ± 0.04 and 0.57 ± 0.09, respectively. Likewise, females laid more eggs in conspecific superparasitism than self‐superparasitism under our experimental conditions. These experiments demonstrate that E. vuilleti females can (i) discriminate between unparasitized and parasitized hosts and adapt the number of eggs they lay accordingly, and (ii) probably discriminate self from conspecific superparasitized hosts. Finally, mating does not appear to influence the host discrimination capacity, the ovarian function, or the oviposition behaviour.     

Impact of mating on Anagyrus kamali Moursi (Hym., Encyrtidae) lifetime fecundity, reproductive longevity, progeny emergence and sex ratio

Abstract: The solitary endoparasitoid Anagyrus kamali Moursi (Hym., Encyrtidae) and the Hibiscus mealybug Maconellicoccus hirsutus Green (Hom., Pseudococcidae), were used as a parasite/host model to test the effect of mating on several fitness parameters, i.e. longevity, lifetime fecundity, progeny emergence and sex ratio. At 27 ± 2°C, 8 h light : 16 h dark, mating significantly affected the survival of male parasitoids. Virgin males lived longer (32.2 ± 9.51 days) than mated males (23.9 ± 7.52 days). Female longevity (40.7 ± 16.3 days for virgins and 36.2 ± 10.7 days for mated females) was not affected by mating. The lifetime fecundity of female parasitoids and their oviposition period was not significantly affected by mating. However, the number of hosts parasitized was greater for mated wasps (7.54 ± 4.85 hosts parasitized/day) compared with virgin ones (5.12 ± 2.19 hosts parasitized/day). This resulted in greater progeny production from mated A. kamali females. The progeny of virgin females consisted only of males, whereas the mated ones had a more female‐biased sex ratio. The lowest sex ratio (0.41 M/F ± 0.123) was attained when females had free access to males and were multi‐mated.     

Sex allocation in a field population of an autoparasitoid

Autoparasitoid wasps lay fertilized eggs in homopteran nymphs, and these eggs develop into female primary parasitoids. Unfertilized, male-producing eggs are laid in immatures of the wasps' own or another primary parasitoid species; males then develop as secondary or hyperparasitoids. In the population of Encarsia pergandiella studied in Ithaca, NY, fertilized eggs were laid in the nymphs of the whitefly Trialeurodes packardi (primary hosts) and unfertilized eggs were laid almost exclusively in pupal females of their own species (secondary hosts). In the two years the population was studied, secondary hosts were always much less abundant than primary hosts at both sites. However, secondary hosts were parasitized at a significantly greater rate than primary hosts. In a laboratory experiment, the encounter rate of females with primary and secondary hosts was not significantly different. Moreover, there was no evidence from the field that wasps found leaves bearing secondary hosts more frequently than leaves without secondary hosts. Dissections of field-collected females showed them to be mated, and thus capable of laying both unfertilized and fertilized eggs. These results suggest that wasps did not encounter secondary hosts at a greater rate, nor were they constrained to lay unfertilized eggs, but rather secondary hosts were preferred. The oviposition sex ratios were influenced by the proportion of secondary hosts, but were less female-biased than would be predicted from the proportion of secondary hosts alone. The results do not support the predictions of Godray and Waage (1990) for either strictly host-limited autoparasitoids (sex ratio should reflect the proportion of secondary hosts) or for egg-limited autoparasitoids (sex ratio should be equal, and independent of the proportion of secondary hosts).     

Sex allocation and effects of superparasitism on secondary sex ratios in the gregarious parasitoid, Trichogramma chilonis (Hymenoptera: Trichogrammatidae)

The role of sex-controlling behaviour at oviposition in generating primary sex ratios, and the effect of larval competition on secondary sex ratios, were studied in the gregarious endoparasitoid, Trichogramma chilonis. The production of a fertilized (female) egg is indicated by the incorporation of a pause in abdominal movements during oviposition, while the absence of it indicates the production of an unfertilized (male) egg. During each ovipositional bout, the first male egg is deposited at the second oviposition, and thereafter at intervals of about eight eggs. This simple pattern enables the wasps to adjust their progeny sex ratios under local male competition to a wide range of host size. Inexperienced wasps do not distinguish between parasitized and healthy hosts. Immature mortality is not significantly different between the sexes when a host is attacked by a single wasp, while females suffer higher immature mortality than males when superparasitism occurs.     

Activity patterns and oviposition rates of Aphytis lingnanensis females,a parasitoid of California red scale Aonidiella aurantii: implications for successful biological control

1. Activity patterns of Aphytis lingnanensis Compere (Hymenoptera: Aphelinidae) females were determined. Females have a preovipositional period of 2–6.5 h and oviposit daily until they die. The average lifetime fecundity was 191 eggs (n = 10 females), with a maximum of 13 eggs per day, but usually far fewer. Females do not lay eggs at night as low light levels reduce the propensity to oviposit. 2. Aphytis lingnanensis females showed a repeatable pattern of activity during the course of the day, ovipositing actively during the first 1.5 h of their 7 h exposure to hosts. Thereafter, activity levels decreased sharply and females spent relatively long intervals resting. Activity occurred in fairly discrete bouts, with long periods of inactivity, ranging from 12 to 231 min between bouts. 3. Each day, females laid most eggs during their first bout of oviposition, with availability of mature eggs in the ovaries dictating the duration and intensity of ovipositional bouts. Once females completed a bout of oviposition in the laboratory, they moved away from the hosts even though many suitable hosts remained. They stood immobile, sheltering, until they matured more eggs. 4. These results suggest how general biological control models and dynamic state variable models of behaviour can be made more realistic. In particular, the behaviour of females does not remain constant over extended periods, particularly because of egg depletion, which suggests that the interaction between the ovipositional history of the individual and its physiological capabilities dictates the response of females to particular circumstances, and thus contributes to patterns of parasitism in the field. 5. It is predicted that A. lingnanensis females in the field are inactive at night and begin ovipositing when it becomes light enough in the morning. Egg depletion is likely if enough hosts are available, but should occur later in the day than was recorded in the laboratory. Egg-depleted females are likely to shelter while they mature more eggs, but may undertake interpatch movement.     

Wild yellow dung fly females may not select sperm based on dung pat microclimate but could nevertheless benefit from polyandry

Molecular techniques have substantially improved our knowledge of postcopulatory sexual selection. Nevertheless, studies examining sperm utilization in natural populations of nonsocial insects are rare, support for sperm selection (biased use of stored sperm, e.g. to match offspring genotypes to prevailing environmental conditions) is elusive, and its relevance within natural populations unknown. We performed an oviposition site choice experiment in the field where female yellow dung flies Scathophaga stercoraria could deposit eggs into three different microenvironments on a dung pat (the east–west ridge, north- or south-exposed side), and genotyped the offspring and sperm remaining in storage after oviposition. Females exhibited plasticity in the number of eggs deposited according to pat age. Additionally, temperature strongly influenced egg placement: the warmer the temperature, the higher the proportion of eggs laid into the north-exposed side of dung. The number of ejaculates in storage differed amongst spermathecae, and females stored sperm from more males than fathered their offspring (2.11 sires vs. 2.84 males within sperm stores). Mean last male paternity was 83.4%, roughly matching previous laboratory estimates. Importantly, we found no evidence that females selectively lay eggs of different genotypes, by biasing paternity towards certain males, depending on offspring’s microclimate. Thus, while we show female choice over number of eggs and where these are deposited, there was no evidence for sperm selection. We further revealed positive effects of multiple mating on total number of offspring and proportion of offspring emerging from the dung. We argue that the integration of field studies and laboratory experiments is essential to promote our understanding of polyandry and cryptic female choice.     

Some factors affecting reproduction and sex-ratio of the predacious mite Amblyseius deleoni (Muma and Denmark) (Acari: Phytoseiidae)

Abstract

Several factors were examined to determine their effect on the reproduction and sex ratio in the predacious mite Amblyseius deleoni (Muma and Denmark), in the laboratory. The factors investigated included multiple matings, duration of copulation, capacity of male for mating in excess of females and age of mating females and males. The factors included also, the host plant leaf texture, food deprivation during immature and adult stages, and prey (Tetranychus urticae Koch) density. The results indicated that females of A. deleoni require multiple matings to maximize their reproductive potential, also when copulation was allowed for increasing periods of time, there was a gradual increase in total egg production and oviposition period. A male showed a high reproductive ability for more than 15 days and was able to mate more than once in excess of females. Age of females has an influence on fecundity and sex ratio; old females decreased egg production and produced proportionally more male progeny compared with young females. Similarly, the highest number of eggs deposited per female A. deleoni was reported, when female mated with a young male (0-day old). In addition, males of A. deleoni (at any age) were able to inseminate the females. Results from host plant leaf texture indicated that guava leaf gave the highest reproduction rate, while the fig leaf gave the least female fecundity. Neither the reproductive rate nor the sex ratio of the progeny of females crossed by normal or experimental males had been influenced by the food deprivation during immature stages. A significant lower fecundity was recorded on female's A. deleoni when exposed to different food deprivation programmes during adult stage. The number of eggs laid by the predator female increased with increasing prey density of T. urtice to a maximum of 2.04 eggs deposited per day at a prey density of 30 protonymphs of T. urticae as a prey. As the level of prey density was increased, there was a shift in sex ratio towards an increased proportion of females.     

Field oviposition rates and egg load dynamics of pollen beetles (Meligethes aeneus Fab.) (Colepotera: Nitidulidae)

Abstract 1 Egg loads from field collected pollen beetles (Meligethes aeneus Fab., Coleoptera: Nitidulidae) were determined by dissecting beetles caught at the beginning and end of the putative daily oviposition period. Field collected beetles were offered Brassica napus (L.) plants in cages for 8 (morning and early afternoon), 16 (overnight), and 24 h to ascertain the number of eggs laid during these time periods. 2 Most eggs were laid in the morning and early afternoon. The proportion of gravid females was higher at the beginning of the oviposition period than at the end. Most females in the morning carried two eggs, whereas one egg was more common in the afternoon. 3 We hypothesized that the number of eggs laid during the oviposition period would be equivalent to the difference between egg loads at the beginning and end of oviposition. This was not the case; differences in egg loads were significantly lower than number of eggs laid. However, the number of eggs laid was equivalent to the egg load at the beginning of the oviposition period, suggesting that eggs available in the morning are laid during the following day. 4 Population estimates of daily oviposition rates, approximately 0.7 eggs per beetle and day, were close to estimates from laboratory studies when the proportion of gravid females was taken into consideration.     

The adaptive significance of mate guarding in the soapberry bug,Jadera Haematoloma (Hemiptera: Rhopalidae)

Male soapberry bugs (Jadera haematoloma)face severe mating competition at the northern edge of their range due to male-biased adult sex ratios. Copulations lasting up to 11 days may serve a mate guarding function (encompassing four or more ovipositions), but copulation duration is highly variable, with some pairings lasting as little as 10 min. Data were gathered to describe factors that influence the reproductive costs and benefits of prolonged copulation. Estimated copulation durations (mean ± SD) were 20 ± 23 h in the lab and 50 ± 8 h in the field and were only weakly affected by sex ratio. Females mated for 5 min produced as many fertile eggs as those mated for 600 min laid; they became depleted of fertile sperm after about 25 days. In twicemated females, the first male's paternity was reduced by about 60%, and all females (N = 13) whose mates were removed experimentally mated again within an average of 6 min. The outcome of sperm competition on a perclutch basis was not highly predictable. The possibility of increased sperm displacement in longer copulations was not tested. Males often guarded females during oviposition and successfully defended them from intruding single males by recopulating. Such intrusions occurred in the majority of oviposition attempts observed in nature. Even though most females mated promiscuously, in a focal aggregation with a mean sex ratio of 2.2 ± 0.4 males/female, the interval between matings by males was commonly several days. Males appeared to respond facultatively to several aspects of the distribution and availability of females. The intensities of mating competition and sperm competition indicate that monogamous mate guarding should be favored over nonguarding in nature. Unpredicted brief. pairings may result from assessment by males of female reproductive value or of their own physical condition, or from female resistance.     

The influence of female age and host size on the sex ratio of the parasitoid Opius concolor

The sex ratio of the progeny of single females parasitizing large hosts favoured the females (sex ratio=0.26); but on small hosts favoured the males (0.73). No differences in mortality of the sexes were detected. The sex ratio was independent of female age when large hosts were used. The percentage of males observed in the progeny of the first day of female oviposition was significantly greater than the mean, irrespective of the age at which female oviposition began. When females were exposed to small hosts, a greater percentage of females was observed in the progeny from the last days of oviposition.

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Résumé L'influence de la taille de l'hôteret de l'âge de la femelle sur le taux sexuel de la descendance a été étudiée sur le parasitoïde Opius concolor Szépl.Le taux sexuel de la descendance des femelles isolées est favorable aux femelles (t.s.=0,26) quand elles ont à leur disposition des hôtes de grande taille, tandis qu'avec des hôtes petits le taux sexuel est favorable aux mâles (t.s.=0.73). On n'a pas détecté de mortalité différentielle des sexes.Les pourcentage de mâles obtenu le premier jour de ponte des femelles sur les hôtes de grande taille est significativement différent de la moyenne, indépendamment de l'âge de la femelle à ce moment. Cependant, sur des hôtes petits, bien que restant favorable aux mâles dans l'ensemble, une plus grande proportion de femelles à partir des premiers jours de ponte a pu être observée.

     

Life History of Bracon hebetor (Hymenoptera: Braconidae) on Plodia interpunctella (Lepidoptera: Pyralidae) on a Dried Vegetable Commodity

Life history of Bracon hebetor Say was studied on Plodia interpunctella Hübner. The life span of female (mean±s.e.) was estimated to be 20.88±0.97 days. The females laid eggs from the first day on after emergence and the oviposition period ranged from 11 to 27 days. But 65% of the total eggs were laid in the first 10 days. The progeny sex ratio (female/total) in the first 15 days was female-bias ranged from 0.51±0.08 to 0.88±0.02, but changed into male-bias ranged from 0.14±0.04 to 0.34±0.12. The overall sex ratio of progeny produced per female was estimated to be 0.66. Total number of progeny per female and net reproduction rate were estimated to be 205.17±13.03 and 136.21, respectively. Other life table statistics were presented.     

The reproductive strategy of the gregarious parasitoid,Pteromalus puparum (Hymenoptera: Pteromalidae)

Summary Host size of Pteromalus puparum, a gregarious pupal parasitoid, shows a wide inter- and intraspecific variation. Experiments were made to study the regulation of the number and sex ratio of progeny per host by the parasitoid. The parasitoid could discriminate inter- and intraspecific size differences of the host and regulate the number of eggs according to the host size when a single female attacked the host. The sex ratio of progeny (proportion males) was about 0.1. The number of progeny laid by the female agreed with the energetically most efficient number og eggs in order to maximize total weight of progeny per host but not with the reproductively most efficient number of eggs to maximize the total fecundity of the progeny. The parasitoid laid smaller number of eggs in a half buried host, but the number was much larger than a half of those in a fully exposed host. When more than one female attacked a single host, the number and sex ratio of progeny per host increased with the number of females attacking the host, but the number of progeny per female decreased. The change of the sex ratio agreed with the prediction of the local mate competition model.     

Comparison of oviposition behavior of a solitary and a gregarious parasitoid (Hymenoptera: Mymaridae)

Anaphes victus Huber andAnaphes listronoti Huber (Hymenoptera: Mymaridae) are respectively solitary and gregarious egg parasitoids of the carrot weevil,Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae). We made detailed ethograms of the oviposition behavior on unparasitized and parasitized hosts for the two species. We then compared the behavior of virgin and mated females for the oviposition of male and female progenies. The two species did not always oviposit after insertion of the ovipositor, but these punctures without oviposition could be readily differentiated from oviposition.A. victus oviposited only once by puncture, whileA. listronoti deposited one to three eggs during the same sequence. The variability of the duration of the various components was generally lower for a given female than between females. Two components, the abdominal vibrations and the pause, were significantly shorter in ovipositions that resulted in male progency for the two species. However, an important overlap in duration prevents using these differences to sex the progeny at oviposition. Virgin females of both species, although capable of producing only males, exhibited both behaviors. Parasitized hosts were recognized through internal and external markings that were used in host discrimination.     

Emergence and mating behavior of the oriental fruit moth Cydia molesta (Lepidoptera: Tortricidae) and its potential for reproduction

The Oriental fruit moth, Cydia molesta (Busck, 1916) (Lepidoptera: Tortricidae), is a key pest of fruit and is widely distributed around the world. There are important connections between its behavior and biology and its management in agriculture, but few studies have investigated the associations between adult behaviors and oviposition. In this study, adult emergence, mating, and reproduction were investigated under laboratory and field conditions. The ratio of females to males at eclosion was approximately 1:1. When one virgin female had access to one virgin male, 66% and 34% of the couples copulated just once and twice, respectively; and the infertility rate of eggs (21.39 ± 1.25%) did not vary daily. Males, given access to one new female daily, could copulate multiple times, whereas females seldom mated more than once, indicating a male-biased operational sex ratio, but mating status of the male parent had no effect on progeny egg reproduction. Also, the number of eggs that hatched by all female partners of a male was inversely proportional to copulation duration for the female laying the eggs for total female reproductive success; and the number of eggs laid by all female partners of a male was proportional to their number of matings for total male reproductive success. However, the total number of eggs that hatched did not significantly differ for eggs laid by a female given new virgin males daily for mating (17.75 ± 4.28) versus eggs laid by virgin females (19.17 ± 7.51) presented daily with a male that re-mated daily with the series of females. Therefore, our results showed that females engaged in mate choice and males engaged in mate competition, affecting egg production, a factor that may be used to enhance mating disruption technology against Cydia molesta.     

The Acp26Aa seminal fluid protein is a modulator of early egg hatchability in Drosophila melanogaster

Drosophila melanogaster male accessory gland proteins (Acps) that are transferred in the ejaculate with sperm mediate post-mating competition for fertilizations between males. The actions of Acps include effects on oviposition and ovulation, receptivity and sperm storage. Two Acps that modulate egg production are Acp26Aa (ovulin) and Acp70A (the sex peptide). Acp26Aa acts specifically on the process of ovulation (the release of mature eggs from the ovaries), which is initiated 1.5 h after mating. In contrast, sperm storage can take as long as 6-9 h to complete. Initial ovulations after matings by virgin females will therefore occur before all sperm are fully stored and the extra eggs initially laid as a result of Acp26Aa transfer are expected to be inefficiently fertilized. Acp26Aa-mediated release of existing eggs should not cause a significant energetic cost or lead to a decrease in female lifespan assuming, as seems likely, that the energetic cost of egg laying comes from de novo egg synthesis (oogenesis) rather than from ovulation. We tested these predictions using Acp26Aa(1) mutant males that lack Acp26Aa but are normal for other Acps and Acp26Aa(2) males that transfer a truncated but fully functional Acp26Aa protein. Females mating with Acp26Aa(2) (truncation) males that received functional Acp26Aa produced significantly more eggs following their first matings than did mates of Acp26Aa(1) (null) males. However, as predicted above, these extra eggs, which were laid as a result of Acp26Aa transfer to virgin females, showed significantly lower egg hatchability. Control experiments indicated that this lower hatchability was due to lower rates of fertilization at early post-mating times. There was no drop in egg hatchability in subsequent non-virgin matings. In addition, as predicted above, females that did or did not receive Acp26Aa did not differ in survival, lifetime fecundity or lifetime progeny, indicating that Acp26Aa transfer does not represent a significant energetic cost for females and does not contribute to the survival cost of mating. Acp26Aa appears to remove a block to oogenesis by causing the clearing out of existing mature eggs and, thus, indirectly allowing oogenesis to be initiated immediately after mating. The results show that subtle processes coordinate the stimulation of egg production and sperm storage in mating pairs.     

Oviposition behavior and progeny allocation of the polyembryonic waspCopidosoma floridanum (Hymenoptera: Encyrtidae)

Oviposition behavior was used to determine the primary clutch size and sex ratio of the polyembryonic wasp Copidosoma floridanumAshmead (Hymenoptera: Encyrtidae) parasitizing Pseudoplusia includens(Walker) (Lepidoptera: Noctuidae). The laying of a female egg was associated with a pause in abdominal contractions during oviposition, while the laying of a male egg was associated with uninterrupted abdominal contractions. Although unmated females produced only male broods, they also displayed male and female egg oviposition movements. Wasps always laid a primary clutch of one or two eggs. For mated females if only one egg was laid, the emerging secondary clutch was all male or female, but if two eggs were laid a mixed brood of males and females was almost always produced. The secondary clutch of single sex broods was usually between 1000 and 1200 individuals, but the secondary clutch of mixed broods averaged 1143 females and 49 males. Thus, the primary sex ratio for mixed broods was 0.5 (frequency males), but the secondary sex ratio was 0.042. Manipulation of the sequence of male and female egg oviposition or of the primary clutch did not produce major alterations in the secondary clutch size or sex ratio.     

Factors affecting progeny production of Anaphes iole

Anaphes iole Girault(Hymenoptera: Mymaridae) is a native, solitaryegg parasitoid of Lygus spp.(Heteroptera: Miridae) in North America. Current research is considering factors thatmay optimize the in-vivo rearing of A.iole using Lygus hesperus Knight(Heteroptera: Miridae) as host. The effects ofhost density, day of oviposition and foodpresence, parasitoid age and mate presence onproduction of A. iole progeny weredetermined in this study. After exposingindividual parasitoids to host patches for 24h, the percentage of hosts containing a latestage A. iole pupa wassignificantly greater at a moderate hostdensity (41–70 eggs per patch) than at a lowdensity (10–40 eggs). But, no differenceswere detected between moderate and high density(71–100 eggs) or between high and low densitytreatments. More adult progeny were generatedby females (of variable age; 0–2 d old) onthe first day of oviposition rather than thesecond day, regardless of food presence. Progeny sex ratio was decidedly male-biased onthe second day. Female age (0 d vs 1 d old)had a marginal effect on production in 24 h; 0d old females tended to generate more adultprogeny than 1 d old females. Overall, thisresearch suggests that exposing newly-emerged,unfed, mated A. iole females to amoderate to high host density for 1 to 2 dcould lead to time-efficient production ofadult progeny in an in-vivo rearing system.     

Egg performance on an egg-carrying bug. Experiments in the field

Selection of oviposition sites has direct influence on female fitness. Differences in offspring survival among sites should favour females to select oviposition sites with the highest survival. Golden egg bug females ( Phyllomorpha laciniata; Coreidae, Heteroptera) use conspecifics as oviposition substrates. Most eggs are laid on the back of the bug but they can be found on all body parts. Females never carry their own eggs, and males commonly carry eggs received without copulation with the donor. We examined differences in egg survival relative to paternity to the egg, host sex and body size and attachment of an egg on a host's body in the field. We also studied which bugs received eggs. Egg loss was surprisingly common: 30–80% of recaptured individuals lost eggs during a six-day period. Unexpectedly, host's paternity to the eggs did not affect egg survival. Also, egg loss did not differ among hosts in respect to other parameters studied. Males received more eggs than females, but survival of the eggs was not better on a male's back than on a female's back. Since egg loss is common in the golden egg bug, we suggest that female oviposition strategy to lay eggs on conspecifics is not perfect. This is due to active behaviour of potential hosts (for example, rejected oviposition attempts) or lack of suitable oviposition substrates (conspecifics) in the field. Since eggs do not survive unless carried, females may be acting opportunistically, doing the best job possible by laying eggs on available conspecifics.     

Reproductive behavior of the honeydew moth,Cryptoblabes gnidiella

Summary

The reproductive behavior of the honeydew moth, Cryptoblabes gnidiella (Millière) (Lepidoptera: Pyralidae), was studied in the laboratory. The sex ratio was 1.1:1, males to females, in both laboratory and field stocks. Most of the females that mated did so during the first night after emergence; males began mating on the following night. Mating occurred 1–2 h before dawn and averaged 100 min. Both sexes mated only once in one night. Most females mated only once in their lifetime, a few mated 2–4 times, whereas males mated up to six times per lifetime. Insects that lived longer also mated more times. When the sex ratio was altered from 3:1 to 1:3, males to females, the percentage of females that mated in one night dropped from 90 to 65, whereas the number of matings per male rose from 0.32 to 2.25. When fresh one-day-old females were provided daily at a ratio of three per male, the males averaged 1.4 matings per lifetime vs. 2.6 with 2- to 3-day-old females. A delay in mating did not affect the percentages of males and females that mated; highest percentages were obtained with 2- to 4-day-old males and females, but a delay in mating resulted in egg fertility dropping from 91 % to 73 %. The preoviposition period lasted a full day after mating, and then most of the eggs were laid during the first night. Average fecundity was 105 eggs per female (maximum: 230).     

寄主大小及寄生顺序对蝇蛹佣小蜂寄生策略的影响

寄主大小模型认为寄生蜂后代性比与寄主大小相关,寄生蜂倾向于在大寄主上产出更多雌性后代,在小寄主上产出更多雄性后代.探讨了以家蝇蛹为寄主时,蝇蛹佣小蜂后代产量和性比变化;单次寄生情况下,寄主大小及寄生顺序对寄生蜂后代性比等影响.结果表明,蝇蛹佣小蜂的产卵期为(8.93±3.34)d,单头雌蜂能产雌性后代(34.11±16.34)头和雄性后代(11.04±8.87)头,且雄性百分比为0.24±0.11.随成蜂日龄的增大,寄生蜂产生雄性后代的比率显著增加.蝇蛹佣小蜂在寄生家蝇蛹时,会优先选择寄生个体较大的蛹;在单次寄生的情况下,蝇蛹佣小蜂倾向于在较大的家蝇蛹内产出更多的雌性后代.