Nicole Hawlitzky

Effects of high temperature shocks on the development and biology ofTrichogramma brassicae [Hym.: Trichogrammatidae]

Trichogramma brassicae Bezdenko is used throughout Europe as an effective biological control agent against the European corn borer (Ostrinia nubilalis Hübner). However, in certain climatic regions, the biological control exerted by this parasitoid is less effective. High temperatures inside the released capsules are suspected to have a negative influence on the parasitoids. To simulate these adverse conditions, we applied heat shocks (35°C and 44°C) for 6 hours to pupae ofTrichogramma brassicae at two periods: white pupae and melanized pupae.The results showed the susceptibility of both the white pupae and melanized pupae, especially at 44°C. At this temperature, the adults (G0 generation) derived from pupae treated at any age showed reduced longevity and fecundity. Moreover, those descended from treated melanized pupae showed an emergence rate lower than that of the control. These effects reduced to half and more the parasitic efficiency of the G0 generation. For the progeny (G1 generation), we observed a decrease of the female ratio: 38% for the progeny of adults derived from treated melanized pupae; 88% for the progeny of those derived from treated white pupae. In that condition, the G1 generation, almost totally male, could not have any parasitic activity.RésuméSuite à une efficacité parasitaire faible des trichogrammes, constatée, dans des conditions climatiques particulières lors des lâchers de ces parasitoïdes contre la pyrale du maïs, des chocs thermiques à 35°C et 44°C pendant une durée de 6 heures sont appliqués au stade nymphal deTrichogramma brassicae Bezdenko. Deux âges sont choisis: nymphe blanche et nymphe mélanisée. Différents critères biologiques ont été étudiés pour la génération G0 ayant subi le choc de température et pour les descendants G1.Les résultats obtenus indiquent une sensibilité des deux âges, surtout à 44°C. Cette température provoque une réduction du pouvoir parasitaire de la G0 de 51% pour les individus issus des nymphes blanches traitées et de 55% pour ceux issus des nymphes mélanisées traitées. Au niveau de la génération G1, on constate une chute de la proportion des femelles dans la descendance des adultes issus des deux âges traités: réduction de 38% pour les individus issus des nymphes mélanisées; 88% pour ceux issus des nymphes blanches. Dans ce dernier cas, la génération G1 pratiquement totalement mâle, est obligatoirement sans efficacité parasitaire.

Antennal olfactory sensilla of the parasitoid fly, Pseudoperichaeta nigrolineata Walker (Diptera : Tachinidae)

Abstract The antennal sensilla of male and female Pseudoperichaeta nigrolineata Walker (Diptera: Tachinidae) were studied by scanning electron microscopy. Five types of sensilla were identified on the funicle. The trichoid sensilla are most conspicuous, with a characteristic distal curvature and wall pores. Basiconic types I and II sensilla show a small peg with a pitted surface. Basiconic type III sensilla can be distinguished from the preceding ones by the swelling of the distal region of the peg. The function of these sensilla is likely to be olfactory. Coeloconic sensilla consist of a short grooved peg sunk in a socket. The number and distribution of the sensilla of each type are described. Female antennae bear more basiconic sensilla than those of males. These results are compared with previously published studies on other muscoid species.

Statistical Study of Trichogramma Brassicae efficiency in relation with characteristics of the European Corn Borer egg masses

The efficiency ofTrichogramma brassicae inundative releases in biological control of the European corn borerOstrinia nubilalis was analyzed in seven plots of 504 plants, each situated in a corn field naturally infested by the European corn borer. Different strategies ofTrichogramma releases were defined on the seven plots. These inundative releases were concluded to be highly efficient even on plots where there were either no parasitoid release or only one parasitoid release at the beginning of the egg mass laying period.

Effects of the egg-larval parasite, Phanerotoma flavitestacea Fisch. (Hymenoptera, Braconidae) on the dry weight and chemical composition of its host Anagasta kuehniella Zell. (Lepidoptera, Pyralidae)

Abstract Effects of the egg-larval parasite Phanerotoma flavitestacea (Hym., Braconidae) on the dry weight and chemical composition of its host Anagasta kuehniella (Lep., Pyralidae) were studied throughout its development using histochemical, histophotometrical and biochemical procedures. The first two methods were only applied to glycogen determination, whereas the third method covered glycogen, lipids and nitrogenous matters. The first two techniques showed that parasitized larvae tend to exhibit more glycogen at certain stages (% of individuals or amount measured in random units). In contrast, Phanerotoma was found following determination to cause a significant decrease in body and component weight. The greater the host age, the greater the difference between control and parasitized larvae (rate of decrease: 75% for glycogen, 77% for nitrogenous matters and body weight, 81% for lipids). At similar weight (analysis of covariance), the differences are no longer significant. Tentative explanations are given in relation to studies by other workers.

Oviposition behaviour inOstrinia nubilaus (Lep.: pyralidae) and consequences on host location and oviposition inTrichogramma brassicae (Hym.: Trichogrammatidae)

Before oviposition, Östrinianubilalis Hübner females sweep the surface of the plant with their abdominal tip extruded. The consequences of such behaviour were studied on host searching and oviposition behaviours of the parasitoidTrichogramma brassicae Bezdenko. Egg-masses ofO. nubilalis, associated or not with sweeping, were submitted toT. brassicae females. The behaviour ofT. brassicae females appeared to be very different between the two situations. The parasitoid in the vicinity of an egg-mass associated with sweeping spent more time on the corn leaf. Ninety percent of females located the egg-mass with sweeping, whereas only 40% located the egg-mass without sweeping. Eighty three percent ofT. brassicae females parasitized egg-masses with sweeping, but only 10% in the case without sweeping. Although no deposit was visible, a chemical trail was probably left behind and was found to arrest the parasitoid, to promote host recognition and to trigger oviposition. The amount of the scales left behind on the corn leaf during the sweeping behaviour was also taken into account but did not appear to constitute the trail. The passage over the trail followed by the egg-mass examination constituted behavioural steps which seemed necessary for oviposition in theT. brassicae femaleRésuméAvant de pondre, les femelles d’Ostrinia nubilalis balayent la surface du végétal avec leur extrémité abdominale dévaginée. Les conséquences d’un tel comportement sont étudiées sur les comportements de recherche et d’oviposition du parasitoïdeTrichogramma brassicae Bezdenko. Les femelles deT. brassicae sont mises en présence d’une ooplaque associée ou non à un balayage. Le comportement des femelles deT. brassicae est très différent entre les deux situations. Le temps de présence du parasitoïde sur la feuille de maïs, à proximité de l’ooplaque associée à un balayage, est plus important. Puis, 90 % des femelles trouvent l’ooplaque contre 40 % sans balayage. Enfin, 83 % parasitent l’oeuf hôte contre 10 % sans balayage. Bien qu’aucun dépôt ne soit visible, une trace de nature chimique est probablement déposée. Le parasitoïde se fixe sur cette trace. Elle favorise la reconnaissance de l’hôte et le déclenchement de la ponte. Le rôle des écailles, perdues sur le maïs lors du balayage, a également été pris en compte. Elles n’apparaissent pas constituer la trace. Le passage sur la trace suivi de la prospection de l’oeuf est une succession d’actes qui semblent nécessaires aux femelles deT. brassicae pour aboutir à l’oviposition

Effect of the juvenile hormone analogue fenoxycarb applied via the host on the parasitoid Phanerotoma (Phanerotoma) ocularis Kohl (Hym., Braconidae)

Abstract Concentrations of 0.001, 0.005, 0.01, 0.05 and 0.1 μg/ml of fenoxycarb (Ro 13-5223) were applied topically to larvae of Ephestia kuehniella Zeller parasitized by Phanerotoma (Phanerotoma) ocularis Kohl. The effect of the treatment and concentration on parasitism rates, preimaginal mortality and emergence rates of the parasitoid were studied comparatively for each larval instar of the host considered. The preimaginal mortality was high when the fenoxycarb was applied on the first larval instar of the host (23–46%) and more higher when applied to the sixth larval instar of the host (40–86%). Consequently, fenoxycarb treatment of the last larval instar of the host produced a reduction in the emergence rate of the parasitoid. Fenoxycarb treatment of the first larval instar of host reduced the effective parasitism rate by P. ocularis . The effect of the solvent, acetone, was also considered.

Statistical analysis of occupancy rates for overdispersed populations by redistribution procedures: application to the European corn borer egg masses distribution.

Standard statistical analyses of distributions of individuals from contingency tables are generally invalid if the individuals are not distributed independently of each other. In this paper, we discuss a method of testing hypotheses about classification category occupancy rates for overdispersed population or for population whose individuals are distributed by groups rather than lonely. These methods are based on population redistribution simulations and provide valid, exact and powerful tests in situations for which classical methods are not appropriate. Illustrations are given from the European Corn Borer eggs data.

Effect of the juvenile hormone analog fenoxycarb on the last larval instar of Ephestia kuehniella Zell. (Lep., Pyralidae)

Concentrations of 0.1, 1 and 10 μg/ml of fenoxycarb (Ro 13–5223) were applied topically to last larval instar of Ephestia kuehniella Zell. Percentage of supernumerary larvae, pupation, emergence and mortality rate were studied, as well as the morphogenetic abnormalities. Larvae treated either remained as permanent larvae or suffered a supernumerary molt (35–70% of the treated larvae). Pupation and emergency rate were very low (10‐0%) and consequently the preimaginal mortality was very high (90–100%). The fenoxycarb treatment produced an intermediate larval‐nymphal form; the percentage of these intermediate forms obtained increased with concentration (20% for 0.1 μg/ml and 40% for 1, 10 μ/ml). The effect of the solvent, acetone, was also considered.

Devenir de l’œuf et comportement de la larve dePhanerotoma flavitestacea [Hym.: Braconidae] lorsque la femelle pond dans des œufs d’Anagasta kuehniella [Lep.: Pyralidae] ayant atteint des stades de développement variés

RésuméQuand des œufs d’âges variés (1 h à 5 j) du lépidoptèreAnagasta kuehniellaZell. sont offerts aux femelles parasites dePhanerotoma flavitestaceaFisch., l’endroit où l’œuf du parasite est déposé, dépend du stade de développement de l’œuf hôte au moment de l’oviposition.Lorsque l’œuf hôte est âgé de 1 h à 3 j, la ponte a lieu dans le vitellus. Par contre, si l’œuf du parasite est déposé dans un œuf âgé de 4 jours ou plus, il est directement pondu dans l’embryon hôte.Selon ces résultats, il semble que la pénétration de l’œuf du parasite ou de la larve est due uniquement à un mouvement passif causé par la migration du vitellus dans le tube digestif moyen de l’embryon hôte.Ces différents points et l’effet de la piqûre de l’ovipositeur sur l’embryon hôte, la nature de l’élimination des larves surnuméraires sont discutés.SummaryWhen lepidopterous eggs of varied ages (1 hour to 5 days) are offered to parasitic females ofPhanerotoma flavitestaceaFisch., the location where the parasitic egg is deposited, depends on the developmental stage of the host egg at the time of oviposition.When the host egg is 1 hour to 3 days old, the laying takes place in the yolk. On the other hand, if the parasite egg is deposited in a four day old or an older host egg, it is directly laid in the host embryo.According to these results, it seems that the penetration of the parasitic egg or larva is only a passive movement caused by the migration of the yolk into the midgut of the host embryo.These different points and the effect of the sting of the ovipositor on the host embryo, the nature of the elimination of the supernumerary larva, are discussed.

Rôles présumés de la membrane embryonnaire d’un parasite ovo-larvaire dePyralidae phanerotoma flavitestace [Hym.: Braconidae]

RésuméAprès l’éclosion de la larve du parasitePhanerotoma flavitestaceaFisch., la membrane embryonnaire persiste pendant 3,5 jours. Différents rôles de cette membrane sont envisagés et discutés. Trois d’entre eux sont retenus (alimentation et protection de la larve parasite et action sur le développement ultérieur de l’hôte). Ce choix est basé sur nos propres observations biologiques et physiologiques et celles de divers auteurs concernant d’autres insectes entomophages.SummaryAfter the hatching of the parasitic larva,Phanerotoma flavitestaceaFisch., the embryonic membrane persists around it during three days and a half. The different hypothetical roles of this membrane are discussed. Three are retained, on the base of our biological and physiological observations interesting this larva or different authors’ observations concerning other entomophagous insects. These roles are alimentary and protective functions for the parasite and action on the host physiology.