Effects of 2,4-D and maleic hydrazide on the glycogen level in the embryonic development of Pimpla turionellae (L.) (Hym., Ichneumonidae)

Abstract: The effects of the herbicides 2,4-D and maleic hydrazide, which are used against wild plants in farming, on the glycogen level in the embryological development of Pimpla turionellae, an important insect species used in biological control programmes, have been investigated. Various concentrations of the applied herbicides decreased the hatching rate and glycogen levels of the eggs which were still going through embryonic development. It was observed that the glycogen level of Pimpla turionellae eggs that were not exposed to herbicides increased after 4 and 8 h during embryonic development, but decreased in the later stages (24 and 30 h). It was found that the hatching rate and glycogen levels throughout the embryonic development decreased with as the concentrations of 2,4-D and maleic hydrazide applied were increased.     

The effects of carbohydrates upon the survival and reproduction of adult female Pimpla turionellae L. (Hym., Ichneumonidae)

In this study the effects of 23 carbohydrates belonging to various groups upon the survival egg production and egg of female adult Pimpla turionellae L. were investigated. The best results among the carbohydrates tested was obtained with sucrose which was also employed as control. Glucose, maltose, trehalose and melezitose on the other hand showed no significant effect. The egg production was observed to be unaffected by glucose and maltose although it showed significant increase with trehalose and significant decrease with melezitose. Fructose and sorbitol caused a significant decrease in the survival of the insect. Fructose and sorbitol did not have any significant effect upon egg production whereas galactose caused a significant decrease. With the exception of galactose, no carbohydrate caused any significant effect upon egg hatching. Although they did not produce any eggs the female insects survived for 13.17, 15.13, 11.58 and 15.83 days in mannose, melibiose, raffinose and mannitol, respectively. The shortest life span was observed in arabinose followed by α-methyl- D -glucoside, dulcitol, rhamnose, cellobiose, xylose, starch, lactose, sarbose, ribose and glycogen.     

DNA gyrase inhibitors: Novobiocin enhances the survival of Pimpla turionellae (Hym., Ichneumonidae) larvae reared on an artificial diet but other antibiotics do not

Effects of novobiocin, nalidixic and oxolinic acids, which are potent antibacterial agents, on the survival and development of the hymenopterous endoparasitoid, Pimpla turionellae L. (Ichneumonidae) were investigated alone by rearing the larvae aseptically on chemically defined synthetic diets. Survival of the fifth instar larvae was not significantly affected by diets with different levels of antibiotics tested. A diet containing the lowest level of novobiocin significantly increased yields of pupae and adults. This level also significantly shortened the developmental time for fifth instar but had no significant effect on complete development of the larvae up to adult emergence. Oxolinic acid at the lowest level did not affect the survival but prolonged development of the insect. In general, the rate of development was significantly increased and the survival was decreased with high levels of the antibiotics. However, nalidixic acid caused a striking decrease in the survival at all tested levels. These results suggest that novobiocin and to a lesser extent oxolinic acid are compatible for addition to artificial diet for rearing P. turionellae , which is an important parasitoid used in biological control.     

Histochemical analysis of accessory genital gland secretions in female Pimpla turionellae L. (Hymenoptera: Ichneumonidae)

The secretions produced by the 3 accessory glands of the female genital tract of Pimpla turionellae were investigated histochemically. The uterus gland secretion was identified as a mixture of hyaluronic acid and lipoprotein, that of the poison gland as a neutral mucoprotein. The product of the alkaline gland (Dufour's gland) consists of lecithin and a cholesterol ester. Pimpla females, as parasites of Lepidoptera pupae, inject these secretions into the host hemocoel during oviposition, thus preventing hemocytic encapsulation of their eggs. The physiological functions of the secretions are briefly discussed.     

Tyloids in Pimpla turionellae (L.) are release structures of male antennal glands involved in courtship behaviour (Hymenoptera: Ichneumonidae)

Morphological and behavioural studies were performed on male antennal tyloids of Pimpla turionellae (L.) (Hymenoptera: Ichneumonidae). S.E.M. and T.E.M. investigations revealed that tyloids, located on 8th and 9th male antennomeres, are release structures of integumentary glands rather than sensory organs. These are bicellular secretory units consisting of one secretory cell, with a well-developed receiving canal, and a canal cell. The latter forms the evacuating canal, which connects the receiving canal to the external pore on the tyloids. Observations of mating behaviour showed that during the precopulatory phase, males typically perform antennal strokes during which the secretion containing tyloids comes in direct contact with the female antennae. Stroking intensity seemed to be correlated with female receptiveness, being more prolonged when females are initially unreceptive. When encountering receptive females, male stroking is usually limited or even omitted entirely. Results from behavioural comparisons between unmanipulated pairs and pairs in which male tyloids had been coated with glue, clearly indicate that the secretion mediates mate acceptance in females.     

Age and diet influence the composition of venom from the endoparasitic wasp Pimpla turionellae L. (Hymenoptera: Ichneumonidae)

Venom from the endoparasitic wasp Pimpla turionellae L. (Hymenoptera: Ichneumonidae) was found to contain a complex mixture of biogenic amines, noradrenalin, phospholipase B, and several proteins and peptides. The amount of noradrenalin and serotonin was found to be highest in venom from newly emerged wasps and decreased with age. Histamine was detected in minute amounts in comparison to the other venom components, and declined with increasing age of the parasitoids. Total peptides and proteins detected by reversed-phase HPLC increased with host age. Old-aged (30-33 days after emergence) wasps contained 2-fold more phospholipase B than young (<10 days [d] old) or medium-aged (10-22-d-old) females. Increases in phospholipase B alone, however, did not account for all changes in total venom protein because by 40 days after emergence, the levels of this enzyme began to decline while the amount of total protein was higher than in younger wasps. For all venom components detected, the amount present in the venom sharply decreased following host exposure. This was presumed to be the result of venom depletion associated with envenomation. Consistent with this view were the modest increases in venom components in wasps displaying a decreased rate of parasitization. When adult females were offered honey alone or in combination with feeding on hosts, no significant changes in venom composition were observed, with the exception of noradrenalin, which was found to be 5 times higher in concentration in wasps fed honey only. These results suggest that wasp age and incidence of parasitism are more important features influencing the composition of venom than the diet of adult females.     

Positive effects of some gyrase inhibitors on survival and development of Pimpla turionellae (Hymenoptera: Ichneumonidae) larvae reared on an artificial diet

Effects of novobiocin, nalidixic, and oxolinic acids on the survival and development of the hymenopterous endoparasitoid Pimpla turionellae L. were investigated alone and in various combinations by rearing larvae aseptically on chemically defined synthetic diets. Effects varied with the levels and kinds of the antibiotics in the tested combinations. Among the tested antibiotics alone, only the lowest level of novobiocin enhanced the postlarval survival. Most of the combinations significantly increased the number of survivors in the postlarval developmental stages. Novobiocin in combination with nalidixic acid (6.0:2.0 mg) in the artificial diet produced a yield of 80.8% pupae and 69.4% adults, respectively. This combination also shortened the developmental time to adult emergence. Similarly, on most of the diets with combinations of the antibiotics, the development of the larvae up to adult stage was noticeably faster than those on the control diets. An approximately equals 50% reduction in the percentages of pupae and adults was recorded by 6.0 mg of novobiocin in combination with 0.75 mg of oxolinic acid compared with the control diet. Although this combination prolonged the complete development of the insect according to other novobiocin and oxolinic acid combinations, developmental time was significantly shorter than that with control diet.     

Antibacterial and antimycotic effect of a newly discovered secretion from larvae of an endoparasitic insect,Pimpla turionellae L. (Hym.)

Three analogues of the peptidyl pheromone, pheromone of Saccharomyces kluyveri, synthesized based on the amino acid sequence proposed by Sato et al. (Agric Biol Chem 45:1531–1533, 1981) were tested for both shmoo-inducing and agglutinability-inducing actions. Purified natural pheromone of the yeast showed the highest activity among the peptides tested. When methionine in the peptides was oxidized, the activity decreased significatly. Pheromone of S. kluyveri induced sexual agglutinability in a cells of Saccharomyces cerevisiae, and shmoo in a cells of S. cerevisiae and S. kluyveri. a Pheromone of S. kluyveri had no agglutinability-inducing action on cells of S. cerevisiae. a Cells of S. kluyveri inactivated only pheromone of the same species, but a cells of S. cerevisiae inactivated pheromones of both S. cerevisiae and S. kluyveri.     

In vivo and in vitro activity of venom from the endoparasitic wasp Pimpla turionellae (L.) (Hymenoptera: Ichneumonidae)

The biological activity of venom from Pimpla turionellae L. (Hymenoptera: Ichneumonidae) was examined in vivo toward larvae and pupae of Galleriae mellonella L. (Lepidoptera: Pyralidae), and in vitro toward bacterial and fungal cultures, as well as cultured insect cells. Pupae of G. mellonella were far more susceptible to the venom than larvae. At low doses of venom [0.1 venom reservoir equivalents (VRE)], pupal abdominal mobility was inhibited within 30 min, and by 24 h, all pupae injected with venom concentrations >0.5 VRE were completely paralyzed. These same doses of venom resulted in an inhibition of adult emergence. Host larvae were far less sensitive to wasp venom as evidenced by all venom injected larvae remaining responsive to mechanical stimulation by 1 h post injection, even at concentrations equivalent to 1 venom reservoir. Eventually (>2 h at 25 degrees C), venom-injected larvae became immobile, then flaccid, and all died within 24 h post-injection. At lower concentrations of wasp venom, the onset of paralysis was delayed by comparison to that evoked by 1 VRE, and few host larvae were able to pupate. Development of host larvae to adult emergence was also reduced in a dose-dependent manner, with eclosion completely prevented at high concentrations (>0.5 VRE) of venom. Venom doses <0.5 VRE did not appear to induce paralysis or alter larval development. When venom was incubated with bacterial or fungal cultures, no antimicrobial activity was detected. However, wasp venom was found to be cytotoxic and cytolytic to cultured cells derived from the cabbage looper Trichoplusia ni Hubner (Lepidoptera: Noctuidae) and the yellow fever mosquito, Aedes aegypti (L.) (Diptera: Culcidae). Though both cell types displayed similar susceptibility in terms of LC50s, the lepidopteran cells responded much more rapidly with regard to the onset of morphological changes and the timing of cell death. A possible mode of action for the venom is discussed.     

Effects of host size on sex ration,development time and size ofPimpla turionellae (L.) (Hymenoptera: Ichneumonidae)

Zusammenfassung Das Geschlechter-Verh?ltnis vonPimpla turionellae (L.) (Hymenoptera: Ichneumonidae) — einem Parasiten vieler Lepidopteren-puppen — h?ngt von der Gr?sse des Wirtes ab, in welchem der Parasit sich entwickelt. In einem kleinen Wirt, wieAnagasta kühniella (Zell.) (Pyralidae), entwickeln sich nur die M?nnchen. In einem mittelgrossen Wirt, wiePyrausta nubilalis (Hbn.),Galleria mellonella (L.)(Pyralidae), Pieris rapae (L.) (Pieridae), undTrichoplusia ni (Hbn.) (Noctuidae), entstehen Weibchen und M?nnchen in gleicher Zahl. In grossen Puppen vonAglais milberti Latr.(Nymphalidae), Malacosoma americanum (F.) (Lasiocampidae) undDanaus plexippus L. (Danaidae) entwickeln sich mehr Weibchen. Im allgemeinen dauerte die Entwicklung in gr?sseren Puppen viell?nger als in kleinen. Das Gewicht des Parasiten nimmt zu mit dem Gewicht des Wirtes Die schwersten M?nnchen wiegen ungef?hr neun mal mehr als die leichtesten.

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Contribution N^o 3783. Entomology Division, Science Service, Department of Agriculture, Ottawa, Canada.     

Interspecific competition between Diadegma semiclausum Hellen (Hym., Ichneumonidae) and Cotesia plutellae (Kurdjumov) (Hym., Braconidae) in parasitizing Plutella xylostella (L.) (Lep., Plutellidea)

Abstract:  Interspecific competition between Diadegma semiclausum and Cotesia plutellae was investigated at 25°C in the laboratory, by exposing the third instar larvae of the diamondback moth, Plutella xylostella to both species together, either species alone or by exposing the host larvae already parasitized by one species, at different intervals, to the other. When host larvae were exposed simultaneously to two species in one arena, parasitism rates of the host by each species were not reduced by the presence of the other species; joint parasitism rate by two species was not significantly higher than that by either parasitoid alone. Both parasitoids could lay eggs into the host larvae which had previously been parasitized by the other species, leading to the occurrence of multiparasitized hosts. When host larvae were parasitized first by D. semiclausum and then being followed within 1–2 h by exposing to C. plutellae , or vice versa, ensuing parasitoid cocoons from the multiparasitized host larvae were nearly all C. plutellae . When host larvae were parasitized initially by C. plutellae and then being followed by D. semiclausum two or more days later, all parasitoids ensued from the multiparasitized hosts were C. plutellae . In contrast, when host larvae were parasitized initially by D. semiclausum and then being followed by C. plutellae two or more days later, most host larvae could not survive to prepupae and most of the ensuing parasitoid adults from the surviving hosts were D. semiclausum . Dissections of host larvae at various time intervals after parasitization by the two parasitoids showed that development of both parasitoids in multiparasitized hosts were somewhat arrested, and that the first instar larvae of C. plutellae could initiate a physical attack on the larvae of D. semiclausum and remove the latter.     

Influence of crucifer cropping system on the parasitism ofPlutella xylostella (Lep., Yponomeutidae) byCotesia plutellae (Hym., Braconidae) andDiadegma semiclausum (Hym., Ichneumonidae)

Field experiments were conducted to study the influence of cabbage monoculture and mixed cropping on the parasitism of diamondback moth,Plutella xylostella (L.), a destructive pest of all crucifers, by 2 larval parasites,Diadegma semiclausum Hellén andCotesia plutellae Kurdjumov. There was no significant difference in parasitism by either species whether cabbage was planted in insecticide-free monoculture or in mixed cropping with 8 noncrucifers which were sprayed twice a week with chemical insecticides mevinphos, methamidophos and permethrin. Population ofP. xylostella increased as the cabbage plants grew older. Parasitism byC. plutellae was higher soon after cabbage transplanting but decreased as the plants grew older. Parasitism byD. semiclausum was very low soon after cabbage planting but increased as the plants grew older. A significant negative correlation was found betwen parasitism byC. plutellae andD. semiclausum. In a caged field study where only one parasite species was used in an individual cage, parasitism ofP. xylostella by both species decreased as theP. xylostella population increased. This is believed to be due to the absence of competition between the two parasites inside the cage. There was no relationship between host-plant age and parasitism ofP. xylostella larvae by either parasite species.     

Influence of different sugars on the longevity of Bathyplectes curculionis (Hym., Ichneumonidae)

Abstract:  Floral nectars, homopteran honeydews and honey are known to increase parasitoid longevity. However, these foods are composed of several sugars which may differentially affect longevity. We tested the effects of individual sugars and mixtures on the longevity of Bathyplectes curculionis Thomson (Hym., Ichenumonidae), a natural enemy of the alfalfa weevil. There was a significant difference in the longevity of female wasps on the various diets. Glucose or fructose alone appeared to have the most benefits while trehalose and melezitose were not as useful for increasing wasp longevity. Suitability of these sugars for provisioning food for parasitoids in the field is discussed.     

Adult size and reproduction in the ectoparasitoid Agrothereutes lanceolatus Walker (Hym., Ichneumonidae)

The effects of adult male and female size on reproductive performance in Agrothereutes lanceolatus Walker, a solitary ectoparasitoid of mature larvae and pupae of several pyralids and tortricids, were investigated. Females had a longer mean lifetime than males. Larger females lived longer, whereas the size of males did not influence the longevity. The number of ovarioles per female did not differ among females of different sizes but larger females carried a greater number of mature and immature eggs. When presented with host cocoons, large females parasitized a higher percentage of hosts than small females. This was due to the fact that larger females accepted more hosts for oviposition whereas smaller ones rejected more hosts. Small and large females used equal numbers of hosts for host-feeding, suggesting that large females removed a greater amount of materials from single hosts through host-feeding.     

Variation in Encardia (Hym., Ichneumonidae) with a key to the species

The Ethiopian genus Encardia Tosquinet is redefined and a key is given to the two species, picta Tosquinet and rufantennata Benoit, now recognised. Type data are given for the twelve nominal taxa now included in E. picta together with data on the three variations found in wing colour pattern.     

Apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae) and its parasitoid Lathrolestes ensator in Dutch apple orchards (Hym., Ichneumonidae, Ctenopelmatinae)

Abstract: Changes in population densities of the apple sawfly Hoplocampa testudinea (Klug) and its parasitoid Lathrolestes ensator (Brauns) were monitored in 15 apple orchards for a period of up to 4 years. The parasitoid species was found in all orchards except one, and was more numerous in plantings on sandier soils. Post‐bloom insecticide applications against other pests, and carbaryl for fruit thinning, often decimated both host and parasitoid in integrated pest management orchards. In organic orchards, where synthetic pesticides are banned, and Quassia is the only remedy against sawfly, the pest is more problematic. The low levels of parasitism in all organic orchards, except one, were possibly due to the application of wettable sulphur during the parasitoid flight period. The sawfly usually recovers more quickly than its parasitoid when chemical control is discontinued, because propagation of L. ensator is limited in various ways. The parasitoid is time limited, because suitable second instar host larvae are rarely available for more than a week on a single apple variety. Moreover, parasitism levels stay moderate because the parasitoid females do not avoid superparasitism. Finally, relatively more sawflies than parasitoids emerge after 10 months underground, because the incidence of prolonged diapause is more elevated in L. ensator than in the sawfly. It is suggested that both the high incidence of prolonged diapause and the inability to avoid superparasitism are useful in reducing the risk of local extinction. Elevated sawfly attack in a single early apple variety would reduce exploitation of suitable host larvae in other nearby varieties, in as far as the parasitoid is not able to distinguish fruitlets with accessible second instar host larvae from those with inaccessible older larvae. Although the former are available for a limited time, the latter may keep the parasitoids from moving to the less abundant second instar larvae in late(r) varieties. Reduction of elevated host density in such an early variety by a properly timed application of a short‐lived pesticide, such as Quassia, increases parasitism levels proportionally, and is expected to promote parasitoid movement to host larvae in other varieties nearby.     

Biology of Campoletis chlorideae (Uchida) (Hym., Ichneumonidae) developing in Bt-treated, Bt-resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract:  Life history parameters in two generations of endoparasitoid Campoletis chlorideae (Uchida) were examined using Bacillus thuringiensis (Bt)-resistant Helicoverpa armigera (Hübner) larvae feeding on B. thuringiensis toxin Cry1Ac. In the laboratory, Bt toxin was fed to Bt-resistant host larvae continuously in case of Bt treatment and only before or after the host larvae were parasitized in Bt–P and P–Bt treatments, respectively. C. chlorideae pupae developed faster in Bt treatment than non-Bt treatment. The shortened pupal stage duration was mainly because of the feeding of host larvae on Bt-diet before being parasitized. Body length of adult male C. chlorideae developed inside Bt-treated Bt-resistant (Bt–Bt) H. armigera larvae significantly decreased, especially in host larvae feeding on Bt-diet after being parasitized. However, survival, pupal mortality and adult longevity of C. chlorideae were almost unaffected in Bt-resistant H. armigera larvae feeding on Bt-toxin. Furthermore, Bt-treated host larvae had the same effect on the F₁ progeny of C. chlorideae as the previous generation, and there was no significant difference between generations. This experiment suggests that there is very limited effect on the life history parameters in two generations of C. chlorideae parasitizing Bt–Bt H. armigera larvae. But both generations of C. chlorideae are affected when Bt-resistant H. armigera larvae fed on Bt toxin for different durations.     

Effects of two neem insecticide formulations on the attractiveness, acceptability and suitability of diamondback moth larvae to the parasitoid, Diadegma mollipla (Holmgren) (Hym., Ichneumonidae)

Abstract:  Behavioural responses of female Diadegma mollipla to volatiles from cabbage plants and host-infested [ Plutella xylostella (L.)] cabbage plants sprayed with two neem insecticide formulations were investigated in a Y-tube olfactometer. Parasitoids were significantly more attracted to volatiles from cabbage and host-infested cabbage sprayed with the powder formulation than to clean air. In contrast, parasitoid response to volatiles from cabbage and host-infested cabbage sprayed with the oil formulation was not significantly different from clean air. In choice tests between infested plants sprayed with water (control) or the powder formulation, parasitoids showed no preference for volatiles from either of the treatments. In similar tests with the oil formulation, parasitoids showed a preference for volatiles from control plants over plants sprayed with the oil formulation. In host acceptance and suitability tests, parasitism rates in the neem- and water-sprayed hosts were, with one exception, not significantly different. However, the neem-sprayed larvae died earlier than control larvae and were therefore not able to support parasitoid development. The implication of these findings for the combined use of neem insecticides and parasitoids in the management of P. xylostella is discussed.     

Impact of the parasitoid Lathrolestes ensator (Hym., Ichneumonidae, Ctenopelmatinae) as antagonist of apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae)

Abstract: Lathrolestes ensator (Brauns) was the only parasitoid species reared from larvae of apple sawfly Hoplocampa testudinea (Klug) collected in Dutch orchards. The life history parameters of apple sawfly and its parasitoid L. ensator were investigated in field and semi‐field experiments. Usually, the adult parasitoids emerge in synchrony with the preferred host stage, the second instar sawfly larvae. Parasitoid females carried 120–175 eggs, but never laid more than half this number. The mortality of sawfly eggs and larvae varied from 75 and 99%. The eggs and mining larvae are most vulnerable, as the older larvae survive for 90% on average. Three factors at least determine how many of the descending larvae become adult sawfly or parasitoid next spring. The failure of descending larvae to construct a cocoon varied from 7 to 31% and was highest in clay soil. Probably a similar mechanical hindrance prohibited more emerging adults, of both sawfly and L. ensator, from attaining the surface in heavier soils next spring. Relatively more sawfly prepupae than parasitoids died in the cocoon stage, from fungus disease or other causes, but more parasitoids than hosts stayed in prolonged diapause. Mainly due to this last factor, the overall result was a decrease of the parasitoid : host ratio during the first season underground. A life table based on survival rates during various life stages yields a net reproductive rate of up to 2.4 daughters per female sawfly. It indicates that 60% of the sawfly larvae need to be parasitized to stop population growth, or correspondingly less when more than 75% of the host eggs and young larvae are killed by predators or other causes.