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Parasitism rates of Bemisia tabaci (Gennadius) and searching and oviposition behaviours of its parasitoid Eretmocerus mundus Mercet were compared on two cassava varieties: a glabrous variety, Nase 4 and a hirsute variety, MM97/0245 with c. 88 leaf hairs/cm². Parasitism was assessed after potted plants of both varieties were exposed in open fields to natural infestation by B. tabaci and its natural enemy. For the behavioural studies, naive, less than 24-h-old females were individually observed on infested cassava leaflets under a microscope for a maximum of 1 h each. The different foraging behaviours were recorded using the computer software 'The Observer 5.0' (Noldus Ltd, Wageningen, The Netherlands). Total per cent parasitism and parasitism by E. mundus did not differ significantly between varieties. Upon encounter with leaf hairs, the parasitoids stopped and groomed before resuming the host search. The frequency of repeat probing, host feeding and antennation after probing and host feeding were higher on the glabrous than on the hirsute variety, while the converse was observed when feeding on liquids on the leaf. The duration of host assessment, initial probing, grooming and resting on the leaf was higher on the glabrous than on the hirsute variety. Leaf hairiness at the density investigated caused some changes in the behaviour of the parasitoids, but did not have an overall effect on field parasitism. Since cassava is generally considered to have glabrous leaves and the variety MM97/0245 is one of the most hirsute varieties, we discount leaf hairiness as a factor in determining levels of parasitoid activity. [ABSTRACT FROM AUTHOR]

Certain carpenter bees (Xylocopa) are characterized by cohabitation of several females in partly common nest structures and/or by the meeting, inside the nest, between adult offspring and their mother. Both conditions are considered to be a basis for social life in bees. In X. pubescens intraspecific competition for nests and nest sites is prominent. Inhabited nests are sometimes usurped, although guarding may exclude females searching for a nest site. After taking over an existing nest the new female removes the brood present and uses the tunnels for her own brood rearing. Emerged offspring are tolerated in the nest by the mother. The juveniles profit in two ways from the foraging by the mother: they receive nectar during trophallaxis and eat from the pollen after it has been unloaded. Young bees may guard the nest while the mother is out, which generally results in trophallaxis after the return of the mother. Trophallaxis with additional offspring is limited; guarding by juveniles is therefore considered to be the result of food competition between the juveniles rather than a novel behaviour pattern. Similarly, the pollen collected by the mother and consumed by the juveniles does not imply a new behavioural programme in the mother but merely constitutes part of her cell provisioning behaviour. As long as her pollen harvest exceeds the consumption by her offspring she will be able to make additional brood cells. [ABSTRACT FROM AUTHOR]

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Wild and cultivated plants in the vicinity of Kibbutz Nahshon and a few additional locations in Israel were sampled for the presence of Bemisia tabaci Genna-dius (Homoptera: Aleyrodidae). The whiteflies, together with their parasites, Eretmocerus mundus and Encarsia lutea, were found to develop on numerous host species throughout the winter. Especially high levels were reached on Lan-tana camara, Abutilon grandifolium and Ipomoea batatas. During late winter and spring the population on these hosts declined. From April onwards the populations increased on potatoes and sunflowers. [ABSTRACT FROM AUTHOR]

Larvae of Spodoptera exigua (Huebner) were collected and their parasites were reared out. From larvae collected in alfalfa fields, 14 parasite species were recovered; from those collected in corn fields, 12 species were recovered; eight species were common to both situations. Meteorus unicolor Wesm. was predominant in corn fields and Chelonus inanitus (L.) was predominant in alfalfa fields. [ABSTRACT FROM AUTHOR]