Wasp Eggs Research Articles

Effects of the feeding process of Ixodes scapularis (Acari: Ixodidae) on embryonic development of its parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae).

The chalcid wasp Ixodiphagus hookeri (Howard) is a parasitoid of several ixodid ticks including the blacklegged tick, Ixodes scapularis Say. We evaluated effects of the feeding process of nymphal I. scapularis on the embryonic development of I. hookeri. Potentially wasp-parasitized nymphal I. scapularis were collected on Prudence Island, RI. Subsamples of the questing nymph cohort were allowed to feed on laboratory white mice. Both the body length and the scutal length of ticks were measured individually for questing nymphs and for feeding nymphs that were removed from hosts at time intervals of 12, 24, 36, 48, and 72 h after attachment. The diameters of wasp eggs they contained were also measured for each designated time interval. There was a positive relationship between the mean scutal index (ratio between body length and scutal length) of ticks and the mean diameter of wasp eggs during 72 h of tick feeding (P < 0.05). Moreover, it appeared that within 24 h of tick attachment, the scutal index of ticks remained unchanged. However, after that period, the scutal index increased significantly (P < 0.05). Diameters of wasp eggs increased continuously during tick feeding and at 72 h after attachment, enclosed eggs and completely formed larvae were found in several ticks. We conclude that factors related to the feeding process of nymphal I. scapularis are necessary to initiate the embryonic development of wasps.

Parasitoids and Polydnaviruses

E ndoparasitic wasps develop within other insects and, invariably, kill their hosts. Because they cause host death, they are unlike other parasites that debilitate but do not kill their hosts; endoparasitic wasps are therefore designated as parasitoids (Godfray 1994). Parasitoid wasps in the hymenopteran families Braconidae and Ichneumonidae carry virus particles that are injected into the host insect in large numbers at the same time that eggs are deposited into the host. In 1965 George Salt, an entomologist at Cambridge University, noted that wasp eggs that were washed free of material from the ovary of the adult female wasp were rapidly encapsulated and killed by blood cells of the caterpillar host; by contrast, eggs that retained the material escaped this fate (Salt 1965). Later, that material was shown to consist of viruslike particles on the surface of the parasitoid egg (Rotheram 1973). Subsequent research efforts have focused on illuminating the role of these particles in regulating the host's physiology during parasitism-particularly their effects on the host's immune system. Only wasp species that develop as internal parasites of other insects, typically flies and moths, harbor these viruslike particles, and flies and moths usually serve as hosts of these virus-carrying parasitoids. The

Envelope protein of parasitic wasp symbiont virus, polydnavirus, protects the wasp eggs from cellular immune reactions by the host insect.

Cotesia kariyai polydnavirus (CkPDV) virions are present in the oviducts of C. kariyai wasp and are injected with eggs into the hemocoel of the host armyworm Pseudaletia separata larvae during parasitization. Evidence that the presence of polydnavirus particles on the surface of the wasp eggs may be essential for prevention of cellular immune reactions by the host hemocytes was obtained by isolating an immunoevasive factor from CkPDV virions. The purified proteinaceous factor protects foreign materials from adhesion and encapsulation by hemocytes of the host P. separata larvae but not by those of common cutworm Spodoptera litura larvae which is an incompatible host for the C. kariyai wasp. Purification procedures consisted of extraction with ethanol/trifluoroacetic acid and reverse-phase high performance liquid chromatography. A factor with a molecular mass of approximately 50 kDa is demonstrated to be present on the envelope of CkPDV virion by immunoelectronmicroscopic observations. Furthermore, immunoreactive proteins are found in plasma of the armyworm larvae but not in the common cutworm larvae, indicating that only the natural host of C. kariyai wasp shares a similar epitope with CkPDV. The sequence of 23 amino acid residues at the amino terminus of the factor was determined to be Ile-Ser-Val-Glu-Asn-Val-Xaa-Thr-Thr-Gly-Ile-Phe-Leu-Asp-Ser-Gly-Glu-Xaa- Val- Pro-Tyr-Ala-Thr-Lys-Pro.

Polydnavirus infection inhibits translation of specific growth-associated host proteins

The wasp Campoletis sonorensis injects a polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. CsPDV protects the wasp egg and larvae by selectively disabling the host's cellular immune response, and by altering host physiology, growth, and development. Among the changes in host physiology brought about by CsPDV infection is a rapid, and specific decline in the translation of fat body mRNAs encoding selected major plasma proteins. Translational inhibition of the synthesis of all storage protein monomers, p82 (Riboflavin binding hexamer), and p74/p76 (arylphorin), occurs upon infection with CsPDV. Moreover, the prewandering peak of the plasma enzyme juvenile hormone esterase (JHE) was blocked by CsPDV injection. Northern blotting of fat body mRNA demonstrated that transcript levels of storage proteins were not affected by infection. Plasma titers of the iron binding proteins transferrin (p72) and ferritin (p24/26), and of the plasma juvenile hormone binding protein (p25) were not changed by CsPDV infection. That storage protein and JHE synthesis are translationally suppressed, while the synthesis of other plasma proteins continues apace, suggests that CsPDV infection may lead to translational discrimination among available mRNAs in CsPDV infected fat bodies. The effect of this translational discrimination is to shunt host resources away from larval growth and adult development, which presumably makes them available to the developing endoparasitoid.

Mobile Parasitoids may Restrict the Spatial Spread of an Insect Outbreak

1. The western tussock moth Orgyia vetusta, a defoliator with flightless adult females, forms localized outbreaks within larger areas of its habitat. These outbreaks may persist for several (> 10) years with little tendency to spread. 2. According to reaction-diffusion models, spatial patterns in population density may arise from the interaction between a mobile predator and a less-mobile prey. This occurs because predators 'spill over' around the edges of prey populations, creating zones in which ratios of predators to prey are elevated. 3. To test this 'predator diffusion' hypothesis for tussock moths, we placed their eggs and larvae along a 500-m transect leading away from the edge of a tussock moth outbreak. through suitable but sparsely occupied habitat. We measured attack rates by a wasp egg parasitoid and four species of tachinid fly larval-to-pupal parasitoids on these experimental immature moths. 4. As predicted rates of parasitism were elevated in the zone surrounding the outbreak. For some parasitoid species, the relationship between parasitism and distance from the outbreak was linear; for others it was parabolic. 5. These results are compatible with several explanations, including the predator diffusion hypothesis. Whatever the mechanism, the results suggest that parasitism restricts the spatial distribution and therefore the global abundance of the host insect in this system.

Natural selection in the laboratory for a change in resistance byDrosophila melanogaster to the parasitoid waspAsobara tabida

The selection response of the polymorphic hostD. melanogaster (Meigen) to the braconid waspA. tabida (Nees) is addressed. Cages of flies with and without wasps were initiated with a population ofD. melanogaster that exhibited variation both in larval foraging behavior and in encapsulation ability. Encapsulation ability was measured as the proportion of parasitized larvae that produce a hardened capsule which encapsulates the wasp egg and ultimately kills the wasp larva. We determined whether the host population changed its encapsulation ability and/or its foraging behavior in response to the wasp. Both species were collected from a local orchard whereA. tabida is the only wasp known to parasitizeD. melanogaster larvae. The naturally occurring genetic polymorphism for rover and sitter larval foraging behavior inD. melanogaster is also found in this field population.A. tabida's vibrotactic search behavior enables it to detect rover more frequently than sitter larvae. Rover larvae move significantly more while feeding than do sitter larvae. In this field population, rover larvae also show higher encapsulation abilities than do sitter larvae. Six cage populations, three without wasps and three with wasps, each containing an equal mixture of rover and sitter flies, were established in the laboratory and maintained for 19 fly generations. Selection pressure in the laboratory was similar to that found in the field population from which the flies and wasps were derived. We found that larvae from cages with wasps developed a significantly higher frequency of encapsulation than those reared without wasps. We were, however, unable to detect a change in larval movement (rover or sitter behavior) in larvae from cages subject to selection from wasps compared to larvae from cages containing no wasps. This may have resulted from a balance between two selective forces, selection against rovers by the wasps' use of vibrotaxis, and selection for rovers resulting from their increased encapsulation abilities

Isolation and characterization of a member of the cysteine-rich gene family from Campoletis sonorensis polydnavirus

The endoparasitic wasp Campoletis sonorensis injects a symbiotic polydnavirus into its host Heliothis virescens. Viral gene expression protects the wasp egg and larva from encapsulation by host haemocytes. Three related C. sonorensis polydnavirus (CsPDV) genes, which are expressed in parasitized H. virescens, have been previously isolated and grouped into a cysteine-rich gene family. In this report, a CsPDV gene encoding an abundant 1.4 kb mRNA expressed in parasitized insects was isolated and mapped to viral segment V (15.2 kb) by Southern blotting and PCR. The VHv1.4 cDNA is 1338 bp long and has an ORF that encodes 322 amino acids with two complete and one partial cysteine motifs. Similar to other characterized CsPDV cysteine motifs, the VHv1.4 motifs are also characterized by six cysteines at conserved positions and variable inter-cysteine amino acids. DNA sequence analyses show that the VHv1.4 gene shares regions of significant identity (73-97%) with the VHv1.1 gene, a member of the cysteine-rich gene family. The VHv1.4 and the VHv1.1 proteins are 62% identical overall; at the N termini including the signal peptide and the N-terminal cysteine motif the identity is greater (90%). Unlike other CsPDV cysteine-rich genes, the VHv1.4 cDNA has two conserved domains (77% identical in nucleotides, 55% identical in amino acids) that presumably result from the duplication of a portion of the gene. The VHv1.4 gene has four introns with splicing sites located at positions similar to VHv11.1 introns. Introns 2 and 3, located in the first and second domains respectively, have greater identity (97%) than the flanking exon sequences (77%). We propose, based on the evidence presented in this paper, that the VHv1.4 gene is a new member of the cysteine-rich polydnavirus gene family.

Regulation of Seed and Pollinator Production in the Fig-Fig Wasp Mutualism

Female agaonine fig wasps enter Ficus fruits (figs), where they pollinate the flowers and oviposit into the ovaries of a proportion of the flowers via their styles. The fig trees are totally dependent on these fig wasps for sexual reproduction, as the wasps fertilize the figs' seeds and transfer pollen between trees, while the wasps need the fig trees' ovaries as feeding sites (galled seeds) for their progeny. Since the wasp progeny destroy seeds, the question arises as to why selection has not led to increasingly higher fig wasp fecundities and the eventual collapse of the mutualism. The stability of the mutualism could be maintained by pollinators having short ovipositors, restricting oviposition to short-styled flowers so that long-styled flowers produce seeds. However, in most of the monoecious Ficus species where measurements were taken, pollinators generally possessed ovipositors of sufficient length to reach the ovaries of a large majority of the flowers. This was confirmed by the presence of pollinator progeny in flowers with long styles. Complete seed destruction may also be avoided by a proportion of fig ovaries being inviolate to oviposition by fig wasps, independent of their style lengths. However, experimental increases in pollinator foundresses per fig in F. burtt-davyi showed that all the ovaries that could be reached by the wasps' ovipositors were potentially exploitable by agaonine fig wasps. Relative production of wasps and seeds was found to be largely dependent on the interplay between the number of eggs inside each wasp, the number of accessible ovaries in individual figs, and the average number of foundresses entering each fig. On average, there were not enough foundresses entering each fig to utilize all accessible ovaries. Possible factors affecting the total entry numbers of wasps into figs include ostiolar closure rates and wasp population densities in the areas surrounding fig trees. As many ovaries remain unused because of a frequent shortage of wasp eggs per fig, fig trees can continue to produce enough seeds for the continued evolutionary stability of the fig-fig wasp mutualism.

Apparent functional role for a cysteine-rich polydnavirus protein in suppression of the insect cellular immune response

Polydnaviruses suppress the cellular immune response and inhibit growth and development in their lepidopteran host, allowing survival of their endoparasitic hymenopteran host. Characterization of genes disrupting insect physiological systems is a major objective in the study of polydnaviruses. Recently, a cysteine-rich gene family encoding a motif composed of invariable cysteine residues flanking hypervariable intercysteine amino acids was described (S.D. Dib-Hajj, B.A. Webb, and M.D. Summers, Proc. Natl. Acad. Sci. USA 90:3765-3769, 1993). They noted similarities to the positive selection pressure for mutations within the vertebrate major histocompatibility complex (MHC) class II genes and speculated that this class of polydnavirus genes may target and disrupt the insect immune system. To study the functional activity of this family of predicted cysteine-rich proteins, the VHv1.1 gene product was produced from bacterial and baculovirus expression systems. Polyclonal antiserum produced from the bacterial fusion protein reacted with a 30-kDa protein from hemocytes, cell-free plasma, and fat body of parasitized larvae. Immunofluorescence analysis of hemocytes from parasitized insects detected the 30-kDa protein bound to granulocytes and plasmacytes. To assay the functional activity of the 30-kDa VHv1.1 protein, a recombinant baculovirus was constructed allowing in vivo expression of the 30-kDa polydnavirus protein from infected insects. Expression of the VHv1.1 protein from the baculovirus system reduced the encapsulation response to washed wasp eggs relative to controls. The experimental evidence demonstrates that Campoletis sonorensis polydnavirus-infected cells secrete VHv1.1 into the hemolymph, where it binds to hemocytes and is associated with the inhibition of the cellular immune response.

Polydnavirus infection inhibits synthesis of an insect plasma protein, arylphorin.

The wasp Campoletis sonorensis injects a segmented, double-stranded DNA polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. After parasitization, CsPDV protects the wasp egg and larva by selectively disabling the host's cellular immune response. Other host physiological systems including growth and development are affected to the apparent benefit of the parasite. To begin the characterization of the biochemical effects and mode of action of CsPDV on host growth, the titre of a developmentally regulated insect storage protein, arylphorin, was studied. Parasitized or virus-infected insects had substantially less circulating arylphorin than control insects. Fat bodies from parasitized larvae also synthesized less arylphorin in vitro. However, Northern blots of total RNA from parasitized and non-parasitized, control insects showed that the arylphorin transcript level was unaffected by parasitization suggesting a biochemical block at the translational level. In vitro translation followed by immunoprecipitation of arylphorin indicated that the mRNA was present and translatable at equal levels in both parasitized and control insects. Injection of purified virus elicited the response observed in naturally parasitized larvae, demonstrating that the effect on arylphorin synthesis is mediated, either directly or indirectly, by polydnavirus gene product(s).

Dynamics ofBlastophaga psenesPopulations, Availability of Caprifigs, and Fig Endosepsis Caused byFusarium moniliforme

Propagules of Fusarium moniliforme, which causes endosepsis of Calimyrna figs, were vectored on the body of the fig wasp pollinators, Blastophaga psenes. Scanning electron microscopy indicated that microconidia and mycelial fragments of F. moniliforme were attached to the wasps' bodies along with grains of pollen. Contamination of adult fig wasps occurred after they emerged from the flower galls, the specialized flowers within a fig syconium in which the wasp eggs hatch and develop. No adult wasps artificially removed from the flower galls were infested with propagules of F. moniliforme but 91-100% of those that emerged from infected syconia of pollinator cultivars (caprifigs) became contaminated

Microbes Associated with Parthenogenesis in Wasps of the Genus Trichogramma

Cytological evidence is presented for a complete correlation between the presence of microorganisms in eggs and the incidence of revertible parthenogenesis (thelytoky) in wasps of the genus Trichogramma. A 2% lacmoid stain was used to visualize microorganisms in wasp eggs. Eggs of all 13 revertible parthenogenetic lines (i.e., lines that can be rendered bisexual by antibiotic treatment) carry microorganisms, while the eggs of all 5 nonrevertible parthenogenetic lines (i.e., lines that cannot be reverted to bisexual reproduction by either temperature or antibiotic treatment) are free of microorganisms. Microorganisms were not detected in eggs of 6 field-collected bisexual (arrhenotokous) lines, nor in those of 3 bisexual lines derived from revertible parthenogenetic lines by antibiotic treatment. The lacmoid stain provides a fast, easy method to detect microorganisms in the Trichogramma eggs and may be used in a modified form for the detection of microorganisms in the eggs of other species.

Consequences Relating to the Inclusion of Female Sarcophagids (Diptera) as Prey by Oxybelus sparideus (Hymenoptera: Sphecidae)

In a 5-yr study, females of the solitary sand wasp Oxybelus sparideus Cockerell included females of one or more sarcophagid flies as prey in 169 of 842 cells. In 17 cells, viviparous maggots emerged from the paralyzed female prey, destroyed the wasp's egg or larva and, in most instances, consumed the prey contents of the cell. Senotainia trilineata (Van der Wulp) adults were reared from maggots collected from two of the cells, Blaesoxipha impar (Aldrich) from one cell, B. kellyi (Aldrich) from one cell, and Helicobia rapax (Walker) from six cells. Two other cells contained maggots that consumed only the wasp's egg and failed to survive; one contained a female Ravinia derelicta (Walker) as part of the prey, the other contained single female R. derelicta and Oxysarcodexia conclausa (Walker). Maggots from the remaining five cells destroyed the prey in the cell but failed to mature. The inclusion of sarcophagid females as prey reduces the number of successful cells of O. sparideus . However, detrimental effects (i.e., the destruction of the contents of those cells by the viviparous maggots) may be offset by the beneficial effects achieved from the use of female sarcophagids because these are rarely used by other Oxybelus . In addition, the capture of females of those sarcophagid species that are cleptoparasitic should reduce the number of cells of O. sparideus and other sphecid wasps normally cleptoparasitized.

Comparative Suitability of Trogoderma variabile and T. glabrum (Coleoptera: Dermestidae) as Hosts for the Ectoparasite Laelius pedatus (Hymenoptera: Bethylidae)

The ectoparasitic wasp Laelius pedatus (Say) had greater success parasitizing the dermestid host Trogoderma variabile Ballion than Trogoderma glabrum (Herbst), a species with similar morphology, behavior, and life history. When T. variabile and T. glabrum larvae or pupae were presented simultaneously, female wasps preferentially parasitized T. variabile. The total numbers of wasp eggs laid and adults eclosing, as well as the percentage of progeny surviving, were significantly reduced on T. glabrum larvae. The developmental periods extending from oviposition to detachment from the host and adult eclosion were significantly longer for wasps developing on T. glabrum than on T. variabile. The venom of L. pedatus also had a less potent effect on larval hosts of T. glabrum than on those of T. variabile. Over a 10-min observation period, a significant percentage of T. glabrum larvae were not paralyzed in spite of having been stung at least once, whereas all the T. variable larvae were paralyzed. Some T. glabrum larvae, representing 13% and 39% of the total numbers parasitized in two separate experiments (but no T. variabile larvae), overcame paralysis and parasitization and subsequently completed adult development. More than half of the “parasitized-recovered” T. glabrum adults failed to reproduce, and the fecundity of those producing progeny was significantly reduced in comparison with beetles from stock culture. The reduced success of L. pedatus in using T. glabrum as a host is likely because of multiple factors including marginal acceptability, resistance to venom, and poor suitability in fulfilling basic physiological requirements necessary for optimum wasp development.

Genetic variation in progeny allocation in Trichogramma maidis

AbstractA considerable amount of work has been recently devoted to the study of progeny allocation strategies by insect parasitoids under different environmental constraints (see Waage, 1986, for a review). All these studies present each of the oviposition strategies (e.g. number of eggs laid per host, superparasitism) as a phenomenon which is progressively settled by natural selection during the course of generations. However, this optimal progeny allocation theory is conceivable only if the variation in wasp's biological traits involved are under a genetic control on which natural selection could act. We have decided therefore to look for a genetic variability in these traits in a Trichogramma maidis Pintureau &amp; Voegelé (Hym.; Trichogrammatidae) population.Based on histological staining which allows to count the number of Trichogramma eggs deposited in each host (Ephestia kuehniella Zeller), we compared different wasp isofemale lines (i.e. families) each of which was submitted to different conditions (i.e. parasite/host ratios).The results show that the control of superparasitism seems to be genetically determined. This appears true both for the average number of eggs deposited in each host, and for the frequency distribution of wasp eggs among hosts.The evolutionary consequences of such results and their possible applications in order to improve the wasp's mass‐rearing conditions are discussed.RésuméVariation génétique de l'allocation à la descendance chez Trichogramma maidisRécemment, de nombreux travaux ont été publiés dans le but de mieux comprendre les différentes stratégies de reproduction (i.e. répartition de la progéniture parmi les hôtes) présentées par les insectes parasitoides sous différentes contraintes environnementales (cf. Waage, 1986, pour une synthèse). L'ensemble de ces travaux considère chacune de ces stratégies (e.g. nombre d'œufs déposés par hôte, décision de superparasiter) comme un phénomène progressivement mis en place par la sélection naturelle au cours des générations. Ceci n'est cependant concevable que si les caractères biologiques en cause chez les parasites sont sous la dépendance d'une variation génétique sur laquelle la sélection naturelle peut agir.Les expériences présentées ici ont donc eu pour but de voir si ces caractères sont effectivement déterminés génétiquement dans une population de Trichogramma maidis Pintureau &amp; Voegelé (Hym.; Trichogrammatidae).Grâce à l'utilisation d'une coloration histologique qui permet de compter le nombre d'œufs de trichogrammes déposés dans chaque hôte, différentes lignées isofemelles (i.e. familles) ont été comparées, et ce selon différentes conditions expérimentales correspondant à différentes valeurs du rapport nombre de femelles parasites sur nombre d'hôtes offerts.Les résultats obtenus montrent que le phénomène du superparasitisme semble être déterminé génétiquement. Ceci est constaté aussi bien au niveau du nombre moyen d'œufs de trichogramme déposés par hôte, que dans les caractéristiques des distributions des œufs de parasites parmi les hôtes.Les conséquences évolutives de tels résultats, ainsi que leurs applications possibles dans le but d'améliorer les conditions d'élevage de masse de ces insectes, sont discutées.

Structure and function of the fig

An overview is given of the functional anatomy of the fig. The fig is the site of pollination and oviposition, it produces wasps, seeds and pollen, and it is the unit of dispersal. Therefore the fig acts as both a flower and a fruit. When a flower is both fertilized and receives a wasp egg, it eventually produces a wasp. Fertilization in flowers that do not recieve a wasp egg initiates seed production. Wide variation exists in the structural features of figs among different subgenera and sections. Monoecious species and gynodioecious species have different strategies for maintaining the symbiosis with the pollinating fig wasps. Monoecious species produce wasps and seeds in a single fig type and show imperfect heterostyly. Gynodioecious species have specialized figs for wasp and for seed production and are characterized by perfect heterostyly.

Segment W of Campoletis sonorensis virus: Expression, gene products, and organization

Campoletis sonorensis virus (CsV, Polydnaviridae) is a segmented double-stranded DNA virus which has an apparently symbiotic relationship with the parasitic wasp, Campoletis sonorensis. CsV replicates in the oviducts of the parasitic wasp and is injected into the wasp's host, Heliothis virescens (Lepidoptera; Noctuiidae), during oviposition. In the parasitized lepidopteran host, the virus has a dramatic effect on host physiology and viral gene products are believed to play an essential role in the survival of the parasitic wasp's egg and larva. In the current study, we used Northern blot analyses to examine expression from segment W in the parasitized host and in the parasitic wasp. Segment W hybridized primarily to two relatively abundant mRNAs (1.6 and 1.0 kb) from the parasitized host. These 1.6- and 1.0-kb mRNAs, which were previously shown to be transcribed from two closely related genes (WHv1 and WHv2) on segment W ( G. W. Blissard, O. P Smith, and M. D. Summers, 1987, Virology 160,120–134 ) increased in relative abundance between 2 and 24 hr postparasitization (pp) and were detected throughout parasitization (8 days). To study the proteins encoded by these closely related genes, the open reading frame from each of the related genes was cloned into a baculovirus expression vector. By pulse labeling in the presence and absence of tunicamycin, we examined secretion and glycosylation of these CsV proteins in infected lepidopteran cells ( Spodoptera frugiperda). Expression of segment W in the oviducts of the female wasp was also examined. Segment W hybridized to at least five CsV mRNAs on Northern blots of poly(A) mRNA from C. sonorensis oviducts. To identify specific CsV mRNAs and map putative viral genes expressed in wasp oviduct tissues, segment W was used to screen a cDNA library of C. sonorensis oviduct mRNAs. Three cDNAs were used to identify CsV mRNAs by Northern blot analyses and to map the locations of three putative CsV genes on segment W. Cross-hybridization within the CsV genome was examined with cloned segment W and with the three cloned cDNAs.

Nesting Behavior of Philanthus sanbornii in Florida (Hymenoptera: Sphecidae)

The activities of an aggregation of Philanthus sanbornii were studied at the Archbold Biological Station, Lake Placid, FL. Females sat head outward in the entrances, investigated conspecific nests, grappled near entrances, removed sand from their burrows, captured honey bees in front of hives, and flew with prey to their nests. Apis mellifera (Apidae) workers and Colletes brimleyi (Colletidae) males comprised 20 and 24 of 49 prey, respectively, with the remainder being a C. brimleyi female, Halictidae, Megachilidae and Anthophoridae. Three long, deep unfinished nests contained terminal storage chambers and from 3 to 8 rearing cells. From 4 to 9 bees, usually of 2 or 3 families, were stored in a cell. The bees were totally or nearly devoid of pollen and some had presumably been cleaned by the wasps in the storage chambers or burrows. The wasp's egg was laid on a bee in the cell in the typical Philanthus position.

Egg production and embryo lethality for habrobracon from biosatellite II and associated postflight vibration experiments

In the reproductive performance of female Habrobracon, striking contrasts were revealed between results from the actual biosatellite flight and those from experiments with the recovered vehicle subjected to forces of simulated launching and recovery. The conditions of the 2 types of experiments differ mainly in influences of orbital flight, of which weightlessness seems most notable. To summarize for the 3 criteria of damage studies: 1. (1) Orbital flight effectively cancelled the characteristic radiation-induced decrease in egg production. On the other hand, the forces of bibration and acceleration improved oviposition only slighty during the more radiosensitive period of the developmental sequence. 2. (2) Excepting metaphase-I results, the only evidence of low hatchability was obtained for an ordinarily invulnerable cell type giving rise to eggs deposited on the 3rd day after biosatellite recovery. Subsequently the hatchability of the haploid eggs was excellent even during the period ordinarily most radiosensitive. In contrast, hatchability data from the simulated flight showed the usual pattern of response except for a moderate alleviation of the senile decline after the 15th day. Death occurred in a variety of stages in eggs from wasps of the simulated flight, but no stage-1 ( i.e. cleavage failure) deaths were obtained during the periods of excellent hatchability of biosatellite wasp eggs. 3. (3) The survival and life span of adult females was excellent and attests to the somatic fitness of experimental wasps. An interpretation of the braconid response to space flight in the presence of chronic γ-ray exposures must explain the unimpaired survival of cell types providing a surprisingly high fecundity, plus the adequacy of these eggs in supporting embryonic development. Possibly under packaged inactivity and weightlessness a stasis of cytological structure provides an opportunity for biochemical mechanisms to repair presumptive radiation lesions. The same stasis may be deleterious to the oocyte-nurse cell complex engaged in vitellogenesis of units destined to be deposited as 3rd-day eggs.

Inhibition of the defense reaction of Drosophila melanogaster parasitized simultaneously by the wasps Pseudeucoila bochei and Pseudeucoila mellipes

The encapsulation reaction normally elicited by the wasp Pseudeucoila mellipes in Drosophila melanogaster fails to occur in hosts parasitized simultaneously or shortly afterwards by resistant Pseudeucoila bochei, but occurs as usual in hosts parasitized by P. bochei that are themselves susceptible to encapsulation. The protection from encapsulation afforded to P. mellipes by P. bochei in the same host is attributed to an active mechanism by which P. bochei protects itself from encapsulation. The possible role of substances elaborated by the wasp egg or female in preventing a successful host reaction is discussed.