Parasitoid behaviour: predicting field from laboratory

Abstract.  1. Most of what is known about parasitoid behaviour comes from laboratory observations: field quantitative observations on searching parasitoids are extremely difficult to do and are rare. The basic components of Aphytis melinus 's response to California red scale ( Aonidiella aurantii ) were studied in the laboratory: encounter, rejection, drumming, probing, oviposition, and host-feeding. It was then asked whether these observations provided a reliable guide to behaviour in the field in a situation that was very different from the laboratory.
2. Field observations were carried out on bark on the trunk and interior branches of trees where live scale density is extremely high in patches, dead scale make up 90% of all scale, and could be expected to interfere with Aphytis search.
3. The laboratory observations predicted well the time taken in the field for each basic event (drumming or probing) and average times spent on a scale. Also well predicted were the distributions of times spent on drumming, probing, and total time on a scale. Rejection rates were much higher in the field. Thus, the laboratory studies predicted foraging behaviour in the field with variable success; potential explanations for observed mismatch between laboratory and field and its possible larger implications are discussed.     

The time and egg budget of Leptopilina clavipes, a parasitoid of larval Drosophila

Abstract.

• 1 For the understanding of the influence of natural selection on the persistence of host selection behaviour in populations of Drosophila parasitoids it is important to know whether parasitoids will become time- or egg-limited. We investigated whether the Drosophila parasitoid Leptopilina clavipes (Hartig) meets egg- or time-limited conditions in the field.
• 2 To this end the following aspects of the parasitoid's life were studied: egg load at emergence, travelling velocity between patches, patch residence times, oviposition rates and life expectancy. Together with the results from earlier studies on host and patch distributions, this formed the input of a ‘Monte Carlo’ simulation model, in which the life history of an individual parasitoid can be traced.
• 3 The simulations revealed that under the conditions found in the field 12.9% of the parasitoid population is egg-limited. The model was also run for a number of scenarios which reflect ‘good’ or ‘bad’ circumstances. In most cases a significant proportion of the parasitoid population proved to be egg-limited.
• 4 For the measurement of travelling velocities and patch residence times a marking method, especially applicable to small-sized parasitoids such as L.clavipes, is described. Marking did not affect survival, host habitat location or host detection rate. Parasitoids were found to be attracted to the odour of fruit-bodies of Phallus impudicus, the most important breeding substrate of their hosts.

     

球体蛛在我国首次发现及一新种记述（蜘蛛目：球体蛛科）

球体蛛在我国首次被发现,本文记述了产于我国海南的纳尔蛛属一新种,定名为华纳尔蛛Wendilgarda sinensis sp. nov.,模式标本保存在河北教育学院生物系。     

The genus Testudinella (Eurotatoria : Gnesiotrocha : Testudinellidae) in North-Eastern India

Nine species and subspecies of the genus Testudinella are reported from North-Eastern India. Of these, six are new to India and eight to the North-Eastern region. Remarks are made on their distribution.     

<Emphasis Type="Italic">Bracon (Lucobracon) iskilipus</Emphasis> sp. n. (Hymenoptera: Braconidae: Braconinae) from the Central Black Sea region of Turkey

During the studies on the Turkish Braconidae, a new species Bracon (Lucobracon) iskilipus sp. n. from the Turkish Central Black Sea region was recorded. Bracon (Lucobracon) iskilipus sp. n. was described, its morphological diagnostic characters were illustrated and it was compared with the related Bracon (Lucobracon) moczari Papp.     

Performance of nymphal and adult Nezara viridula on selected alternate host plants

Laboratory studies with the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), feeding on seeds or fruits of some alternate host plants, demonstrated differences in nymphal survival and development time, and body weight at adult emergence. Lowest mortalities (25%) were observed for nymphs on fruits of dakota mustard [Brassica kaber (DC.)] and siberian motherwort (Leonurus sibiricus L.). On fruits of castor bean (Ricinus communis L.) nymph mortality was ca. 60%, and on mature seeds of L. sibiricus ca. 75%. Total development time from second instar to adult ranged from ca. 26 days on B. kaber to ca. 42 days on R. communis. Fresh body weight at adult emergence was greatest for nymphs on L. sibiricus and lowest on R. communis. Adult survival after 30 days and mean longevity was greater on L. sibiricus than on the remaining foods, being drastically reduced on R. communis. In general, reproductive performance on all foods was similar, except R. communis, on which no female reproduced. Female weight gain of N. viridula was generally greater on L. sibiricus On R. communis, adults lost weight during their first week and showed the lowest weight gain at the end of day 29. Field observations coupled with these laboratory studies suggest that in the Warta area (northern Paraná state, Brazil, 23° 11 S), L. sibiricus and B. kaber are important alternate food plants in the seasonal phenology of N. viridula. R. communis, however, is of poor nutritional quality, serving primarily as a refuge.

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Résumé L'alimentation au laboratoire de N. viridula avec les graines et les fruits de diverses plantes a entraîné différentes mortalités larvaires, différentes vitesses de développement et des différences dans les poids des adultes à l'émergence. Les mortalités les plus faibles (25%) on été observées avec les fruits de Brassica kaber DC. et de Leonurus sibiricus L.Avec les fruits de Ricinus communis L., la mortalité larvaire était de 60%; sur graines mûres de L. sibiricus, elle était de 75%. La durée du développement du second stade à l'adulte a varié de 26 jours sur B. kaber à 42 jours sur R. communis. Le poids frais des adultes à l'émergence était le plus élevé avec L. sibiricus et le plus faible avec de R. communis. La longévité des adultes au-delà de 30 jours était la plus élevée avec L. sibiricus, et était fortement réduite avec R. communis. Dans l'ensemble, la reproduction était de même importance avec les différents aliments, à l'exception de R. communis avec lequel les femelles ne se reproduisaient pas. Le gain de poids des femelles était généralement supérieur avec L. sibiricus; avec R. communis les adultes ont perdu du poids pendant la première semaine et ont présenté le plus faible gain à la fin du 29ème jour.Des observations dans la nature, associées à ces expériences de laboratoire, laissent supposer que dans la zone de Warta (au Nord de l'état de Paraná, 23° 11 S, au Bresil), L. sibiricus et B. kaber sont des plantes hôtes alternatives importantes dans la phénologie saisonnière de N. viridula. Cependant, R. communis, de faible valeur alimentaire, sert avant tout de refuge.

     

Effects of pre-adult and adult experience on host acceptance in choice and non-choice tests in two strains ofTrichogramma

The effect of adult learning through an oviposition experience, and pre-adult learning through development inside a host was investigated in two strains of an Australian egg parasitoid,Trichogramma nrivelae (Hymenoptera: Trichogrammatidae). Host response was measured in two types of laboratory preference tests. In single host tests, females reared on three lepidopteran hosts (Heliothis punctigera (Noctuidae),Papilio aegeus (Papilionidae), andHypolimnas bolina (Nymphalinae)) were presented host eggs individually, and allowed two ovipositions. Pre-adult experience affected host preference in only one strain, while acceptance of a host was increased in both strains when they had previously oviposited in this host species. An oviposition experience had a stronger effect on host preference than pre-adult experience. In choice tests, pairwise combinations of hosts were arranged in an alternating grid. The ratio of host acceptances to host contacts was computed for the whole test and up to the first oviposition. These indicated that effects of rearing host were weak or absent, but the host chosen initially had a strong effect on host preference. Relative size of the hosts had a strong effect on choice of the first host. The implications of learning inTrichogramma are discussed in relation to host preference testing procedures and the selection of candidate strains for mass rearing and inundative release.