Mating Status and Choice of Group Size in the Phoretic Fly Norrbomia frigipennis (Spuler) (Diptera: Sphaeroceridae)

The phoretic sphaerocerid fly Norrbomia frigipennis mates on scarabid dung beetles, follows them underground, and lays eggs in the collected dung. We found that male and female flies distribute themselves nonrandomly on beetles with respect to fly group size. The proportion of virgin females increased with group size, and females with mature eggs were most frequently found on beetles carrying fewer flies. Laboratory experiments revealed that mated females avoided larger groups, virgin females seemed to prefer large groups and mated females, small groups. Males showed no such pattern. These results suggest that N. frigipennis can estimate group size, presumably an adaptation with a reproductive function. However, flies did not join hosts on the basis of the sex of already mounted flies.     

Size specific demography of three species of Anastrepha fruit flies

Individuals of three Anastrepha species: A. obliqua, A. ludens, and A. serpentina (Diptera: Tephritidae), were sorted according to pupal weight in cohorts of large and small flies. Demographic parameters and reproductive patterns and heterogeneity were determined for each cohort. Large flies of the three species presented greater expectation of life and gross fecundity rates. A. ludens was the species with the longest life span (expectation of life of large adults was 110 days) and the greatest gross fecundity rates (1597 eggs/female for the large flies). While, A. obliqua had the shortest mean age of reproduction (33 days), and the greatest daily egg production (14 eggs/female/day). Net fecundity was similar in these two. A. serpentina had lower fecundity rates.Reproductive information for each size and each species include: age-by-parity relations, fraction of sexually mature life in which females lay eggs, and frequency distribution of individual egg production. Results demonstrate that even under constant laboratory conditions and using standard artificial hosts, there is a great deal of life history variation among these Anastrepha species and among other tephritid fruit flies.     

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).     

Visual and Chemical Cues Used in Host Location and Acceptance by a Dipteran Parasitoid

Locating potential hosts for egg laying is a critical challenge in the life history of many insects. Female insects in several orders have evolved mechanisms to find hosts by using olfactory and visual signals derived from their hosts. We describe visual and chemical cues used by the dipteran parasitoid Apocephalus paraponerae (Diptera: Phoridae) in the location and acceptance of its host ant Paraponera clavata (Hymenoptera: Formicidae: Ponerinae). Our results show that A. paraponerae uses the visual cue of ant body size when locating hosts at short range and that these flies lay more eggs in ants that retain their surface chemicals than in ants with these chemicals removed. We compare the cues used by A. paraponerae with cues used by tephritid fruit flies in location and acceptance of their hosts, and we suggest further avenues for the study of host location, acceptance, and host discrimination of A. paraponerae and other parasitoids of ants.     

Intra- and interspecific competition by Fopius arisanus and Diachasmimorpha tryoni (Hymenoptera: Braconidae), parasitoids of tephritid fruit flies

Fopius arisanus (Sonan) and Diachasmimorpha tryoni (Cameron) are two important solitary endoparasitoids of tephritid fruit flies. The former species attacks host eggs while the latter attacks host larvae, and both species emerge as adults from the host puparium. This study investigated intrinsic competition between these two parasitoids, as well as aspects of intraspecific competition within each species in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Parasitization by F. arisanus resulted in direct mortality of host eggs and prolonged development of host eggs and larvae. Superparasitism by F. arisanus was uncommon when mean parasitism per host patch was <50%, but increased with rising rates of parasitism. Superparasitism by D. tryoni was more common. In superparasitized hosts, supernumerary individuals of F. arisanus were killed through physiological suppression, while supernumerary larvae of D. tryoni were killed mainly through physical attack. In multiparasitized hosts, dissections showed that 81.6% of D. tryoni eggs in the presence of F. arisanus larvae died within 3 days, indicating physiological inhibition of egg hatch. Rearing results further showed that F. arisanus won almost all competitions against D. tryoni. The ratio of D. tryoni stings to ovipositions was lower in hosts not previously parasitized by F. arisanus than in parasitized hosts, suggesting that D. tryoni can discriminate against parasitized hosts. The mechanism that F. arisanus employs to eliminate D. tryoni is similar to that it uses against all other larval fruit fly parasitoids so far reported. The results are discussed in relation to the competitive superiority of early acting species in fruit fly parasitoids, and to a possible competitive-mediated mechanism underlying host shift by D. tryoni to attack non-target flies following the successful introduction of F. arisanus in Hawaii.     

Larval parasitoid uses aggregation pheromone of adult hosts in foraging behaviour: a solution to the reliability-detectability problem

Parasitoids that forage for herbivorous hosts by using infochemicals may have a problem concerning the reliability and detectability of these stimuli: host stimuli are highly reliable but not very detectable at a distance, while stimuli from the host's food are very detectable but generally not very reliable in indicating host presence. One solution to this problem is to learn to link highly detectable stimuli to reliable but not very detectable stimuli. Ample knowledge is available on how associative learning aids foraging parasitoids in the location of suitable microhabitats. However, in this paper we report on another solution to the reliability-detectability problem and present evidence for an essential, but as yet overlooked, aspect of Drosophila parasitoid ecology. For the first time it is shown that a parasitoid of Drosophila larvae spies on the communication system of adult Drosophila flies to locate potential host sites: naive parasitoids strongly respond to a volatile aggregation pheromone that is deposited in the oviposition site by recently mated female flies. Thus, the parasitoids resort to using highly detectable information from a host stage different from the one under attack (i.e. infochemical detour). The function and ecological implications of these findings are discussed.     

Accessory gland secretory proteins in relation to fitness parameters of Drosophila ananassae and D. varians

Developmental morphometry, qualitative and quantitative analysis of the accessory gland secretory proteins, fecundity and productivity in relation to protein ejected during subsequent (first to fourth-time) matings have been studied in Drosophila ananassae Doleschall and Drosophila varians Bock. In both species, size and secretion of accessory glands increases from 1 to 8 days and the stored secretion ejected from males to the female genital tract during subsequent mating varies. The maximum number of eggs and flies are produced from the females mated with bachelor males and it is a minimum when virgin females are mated with fourth-time mated males. Sodium dodecylsulfate–polyacrylamide gel electrophoresis analysis of accessory gland secretory protein patterns and their glycosylation differs in both the species. Correlation coefficient analysis between gland size and quantity of secretion, percentage of secretory protein transferred per mating, and eggs and flies that emerged showed a highly significant, positive relationship. Among different matings, the number of eggs laid and flies that emerged per female between subsequent (first to fourth-time) matings of males was found to be highly significant and the difference between fecundity and productivity between the two species was highly significant.     

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.     

Reproductive biology of Fopius ceratitivorus (Hymenoptera: Braconidae), an egg–larval parasitoid of the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The reproductive biology of Fopius ceratitivorus Wharton, a recently discovered African parasitoid, was studied in quarantine in Hawaii to facilitate its mass production for biological control of the Mediterranean fruit fly, Ceratitis capitata. Mean longevity of host-deprived and ovipositing females was 17.3 ± 0.9 d and 16.2 ± 0.5 d, respectively. Ovarian maturation peaked at 61.6 mature eggs per female on the fifth day after eclosion and declined thereafter. Mean number of offspring produced per day by mated females was 5.1 ± 0.4, and realized fecundity expressed as total eggs deposited during the female’s life time was 107.8 ± 12.8. Females were more attracted, to and reproduced significantly more, in fruit substrates containing odors of adult flies and eggs rather than fruit substrates artificially inoculated with fly eggs. Our findings suggest that F. ceratitivorus is a promising new parasitoid for biological control of C. capitata in Hawaii.     

CORRELATED RESPONSES IN LIFE-HISTORY TRAITS TO ARTIFICIAL SELECTION FOR BODY WEIGHT IN DROSOPHILA MELANOGASTER

Drosophila melanogaster that had been successfully selected on rich and poor larval medium for increased and decreased fresh weight at eclosion were tested on an intermediate medium for correlated responses in longevity, fertility, and hatchability. Larger flies laid more eggs early in life and lived shorter lives than smaller flies, which not only lived longer but also laid more eggs later in life. This supports the notion of a mortality cost of reproduction in Drosophila. The total number of eggs laid per lifetime did not differ between the two groups. The percentage of offspring hatched started at normal levels (about 50% of eggs laid), then declined rapidly in large flies. In small flies, hatchability started at a lower level early in life (40-65%), but declined less rapidly, and later in life was higher than the hatchability of eggs laid by larger flies.     

Life-cycle of Suidasia medanensis (=pontifica) (Acari: Suidasiidae) under laboratory conditions in a tropical environment

The life cycle of Suidasia medanensis (= pontifica) was studied under laboratory conditions at 26°C and 86% relative humidity. Freshly laid eggs were observed until they developed into adults and the periods between stages were recorded. Production of eggs by mated females was monitored until they died. The eggs required an average of 12.6 ± 0.6 days to develop into adults. Mean longevity of mated females and males was similar (48.6 ± 13 and 49.1 ± 20 days, respectively). The conditions used in this study may be considered optimal for in vitro culture of S. medanensis.     

Multiple matings increase the fecundity of the yellow swallowtail butterfly,Papilio xuthus L., in summer generations

Females of the yellow swallowtail butterfly, Papilio xuthus,were reared in the laboratory. They were divided into four groups held under different mating conditions: nonmating (virgin) and mated once, twice, and three times. The number of eggs in the ovaries was counted by dissection. Virgin females produced increasing numbers of mature eggs, up to about 30, in the week following emergence. When the female had mated once, the number of mature eggs was significantly higher than that of virgin females by the second day after emergence. However, the double- and triplemated females did not increase the number of eggs in each state further than the singlemated females. The double-mated females deposited significantly more eggs than the singlemated females in the laboratory. The triplemated females also deposited more eggs on the day after the third mating than the doublemated females. Thus, multiple matings increased the number of eggs deposited. The change in the hatchability and the morphology of the spermatophore in the bursa copulatrix suggested that the sperm from the last mating had precedence.     

Does superparasitism improve host suitability for parasitoid development? A case study in the Microplitis rufiventris-Spodoptera littoralis system

Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host. Recent studies have shown that allocation of additional eggs to an already parasitized host may be beneficial under certain conditions. In the present work, mortality of Microplitis rufiventris wasps was significantly influenced by both host instar of Spodoptera littoralis larvae at parasitism and level of parasitism. In single parasitization, all host instars (first through sixth) were not equally suitable. Percentage of emergence success of wasp larvae was very high in parasitized first through third (highly suitable hosts), fell to 60% in the fourth instar (moderate suitable) and sharply decreased in the penultimate (5th) instars (marginally suitable). Singly parasitized sixth (last) instar hosts produced no wasp larvae (entirely unsuitable), pupated and eclosed to apparently normal adult moths. The scenario was different under superparasitism, whereas supernumerary individuals in the highly suitable hosts were almost always killed as first instars, superparasitization in unsuitable hosts (4th through 6th) had significant increase in number of emergence success of wasp larvae. Also, significantly greater number of parasitoid larvae successfully developed in unsuitable hosts containing three wasp eggs than counterparts containing two wasp eggs. Moreover, the development of surplus wasp larvae was siblicidal in earlier instars and nonsiblicidal gregarious one in the penultimate and last “sixth” instars. It is suggested that the optimal way for M. rufiventris to deal with high quality hosts (early instars) is to lay a single egg, while the optimal way to deal with low quality hosts (late instars) might be to superparasitize these hosts.     

Attraction of Mexican Fruit Flies (Diptera: Tephritidae) to Grapefruit: Enhancement by Mechanical Wounding of and Experience with Grapefruit

Wild strain, mated, female Mexican fruit flies, Anastrepha ludens (Loew), with no prior experience with fruit (naive), were not attracted to grapefruit, a preferred cultivated host, in wind tunnel experiments. Naive, mated laboratory strain females were attracted. Prior experience with grapefruit increased attraction of both laboratory and wild strains. More females were attracted to fruit with peel damage than to undamaged fruit, indicating that fruit odor mediated attraction. More naive than experienced females attempted to oviposit on the sides of the wind tunnel. Experienced laboratory males, but not wild males or naive males, were attracted to grapefruit. Attraction and oviposition behavior of laboratory flies was greater than that of wild flies.     

Abnormal egg-laying behaviour of female carrot flies (Psila rosae) induced by the fungus Entomophthora muscae

Female carrot flies (Psila rosae F.) infected with Entomophthora muscae (C.) Fres. on days 1 to 4 of adult life were unable to lay their eggs near the food plant. Flies infected on day 5 of adult life showed an egg-laying behaviour similar to that of uninfected flies. E. muscae-infected female carrot flies caught in the field showed an egg-laying behaviour comparable to that of the flies infected in the laboratory during the first day of their live.Eggs laid by infected females were equally as fertile as eggs laid by uninfected females, and developed into normal flies.It is concluded that female carrot flies infected with E. muscae in the field do not in general contribute to the development of the carrot fly population, due to their abnormal egg-laying behaviour.

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Zusammenfassung Wenn Weibchen der echten Möhrenfliegen (Psila rosae) zwischen den ersten und der vierten Tag in dem Laboratorium mit E. muscae infiziert worden waren, könnten sie ihre Eier an den Futterpflanze nicht ablegen. E. muscae-infizierte Weibchen, die ins Feld gefangen worden waren, zeigten auch ein abweichendes Eiablageverhalten. Ihr Behalten war mit dem Verhalten von Fliegen vergleichbar, die an ihrem ersten Lebenstag im Laboratorium infiziert worden waren.Von infizierten Weibchen gelegte Eier waren ebenso fruchtbar wie die von nicht infizierten Weibchen gelegten Eiern. Es wird konkludiert, dass E. muscae-infizierten Weibchen der echten Möhrenfliegen der Entwicklung der Population keinen Beitrag leisten.

     

Trapping oestrid parasites of reindeer: the relative age, fat body content and gonotrophic conditions of Cephenemyia trompeand Hypoderma tarandifemales caught in baited traps

Abstract. Dissection of flies caught in northern Norway revealed that only mated, gravid females of H.tarandi (L.) and larviparous C.trompe (Modeer) were caught in host-mimicking C0₂-baited traps. Trapped females had the same gonotrophic and fat body (FB) conditions as females caught on and around reindeer. Most trapped females of both species were of middle to old age, having only one-half to no FB reserves left and only a few to moderate numbers of eggs or larvae remaining. Most young females trapped also had previously oviposited or larviposited at least once, and some newly eclosed, mated females were present throughout the fly season. Based on the known location of reindeer herds, it was evident that trapped flies that had recently oviposited or larviposited had dispersed into the trapping area from 25–100 km away. Declining FB reserves sustained wild-caught C.trompe females (and in utero larvae) in the laboratory for 14 days and H.tarandi females for 18 days. Reserve FB also was depleted during long flights. Females of both species that flew for the longest times (5.1–11.7 h) on a laboratory flight mill had low FB reserves, but nearly maximum numbers of eggs or larvae. Conversely, most females that flew for less than 5 h on the flight mill had little or no FB remaining, and few eggs or larvae. The large FB reserves accumulated as larvae feed in the vertebrate host enable the non-feeding adults to survive and infect their hosts even after prolonged periods of flight-inhibiting climatic conditions.     

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.     

广聚萤叶甲成虫交配时长对产卵量与孵化率的影响

【目的】明确不同交配时长对广聚萤叶甲雌虫产卵量和卵的孵化率的影响。【方法】在室内条件下,对不同交配时长下广聚萤叶甲的雌虫产卵量和卵的孵化率进行观察:(1)选取羽化第3d的广聚萤叶甲雌雄虫随机配对,观察24 h,记录交配情况和时长;(2)在交配开始1、5、15、30、60 min时,强行分开雌雄成虫,然后将不同交配时长的雌虫进行单独饲养,以正常交配一次的雌虫作为对照,每个处理选取23组;(3)将15～30 cm健壮豚草小苗插入注满水的塑料小瓶内,将配对的一组雌雄成虫和豚草小苗放入养虫盒中饲养,每天更换带卵的小苗并记录叶片上的产卵量;(4)将上述带卵的小苗至于适宜条件下培养,记录5～7 d内卵块孵化的情况。【结果】广聚萤叶甲正常交配一次的对照组的产卵水平显著高于各处理组,单雌产卵为889粒,交配时间15 min以下各组雌虫的产卵量明显低于交配30 min以上的各组雌虫。同时交配时长5 min以下雌虫产的卵基本不能孵化,而交配时间达到30 min以上的各组卵块的孵化率明显提高。【结论】雄虫转移雌虫受精所需精子量需要耗费的时间为30 min左右,且雄虫有延长交配时间的趋性。该结果为研究广聚萤叶甲的生态特性以及优化种群繁殖提供科学依据。     

Rhythmicity of mating and oviposition inCallosobruchus subinnotatus (Pic) (Coleoptera: Bruchidae)

Mating and oviposition behaviors were studied inCallosobruchus subinnotatus. Copulation was most frequent during the late scotophase, 2–3 h before onset of photophase. The females were less willing to mate during photophase, which increased the time to initiate mating while decreasing the duration of mating. Females exhibited increased movement prior to mating, resting immediately after mating, and remained stationary for 6 h when oviposition commenced. Multiple mating by both males and females affected the number of eggs laid, duration of mating, and uncoupling time at the end of mating. Females that mated two or three times laid more eggs than females that mated once or more than three times. Females that remainedin copula for less than 18 min showed greater readiness to remate than those that remainedin copula longer. There was a gradual decrease in the number of eggs females could lay with an increase in the number of previous matings by males.     

Egg Size, Intrinsic Competition, and Lethal Interference in the Parasitoids Encarsia pergandiella and Encarsia formosa

Recent population dynamic theory predicts that disruption of biological control may occur when one parasitoid species' superiority in intrinsic competition is associated with a lower ability to find and exploit hosts (i.e., ability in extrinsic competition). One might expect such a trade-off, for instance, if parasitoids with larger (and fewer) eggs are more likely to prevail in intrinsic competition than species with smaller (and more numerous) eggs. We tested the idea that relative egg size could be used to predict the outcome of intrinsic competition in two closely related endoparasitoids, Encarsia pergandiella Howard and Encarsia formosa Gahan. Contrary to expectation, the parasitoid species with smaller eggs, E. pergandiella, prevailed in intrinsic competition, regardless of the order that hosts were exposed to the two species. In a literature survey, we found four studies of competing pairs of endoparasitoid species for which: (a) egg size estimates were available and (b) one species was consistently superior in intrinsic competition. In three of the four studies, the small-egged species prevailed in intrinsic competition, as we also found. Although E. formosa lost in intrinsic competition, this species negatively affected E. pergandiella's progeny production by host feeding on and killing hosts containing E. pergandiella eggs. E. formosa females also host fed on conspecific-parasitized hosts. As a mechanism of both intra- and interspecific interference competition, host feeding on parasitized hosts contradicts assumptions about the nature of interference competition in existing population dynamics models.