Bethylid wasps are a medium sized family of parasitic Hymenoptera, with biological control potential, which have recently proved excellent model systems for testing evolutionary and life history theory. We report observations on a species of Laelius from The Netherlands. The species is morphologically indistinguishable from Laelius pedatus, previously reported only from the New World. Reciprocal crosses between the Dutch wasps and L. pedatus from Madison, Wisconsin, USA confirmed that the Dutch population belongs to L. pedatus. We compared the life history of the Dutch wasps with those from Madison by rearing them on Trogoderma glabrum, but found no significant differences. The Dutch wasps successfully parasitize Trogoderma angustum, an invasive museum and domestic pest found in situ, but suffer high developmental mortality on T. glabrum. Wasp egg size was positively correlated with the size of ovipositing female, which was also negatively correlated with the developmental mortality of offspring. Larger wasps also carried more mature eggs. Time taken to lay the clutch increased with the size of the eventual clutch laid and was longer in unmated than mated females. When some wasps died before completing development, surviving members of the brood grew to a larger size and took longer to complete development. The number of males per brood increased with previous oviposition experience, an indication of sperm depletion through life. We discuss the implications of these trends for parasitoid life history theory.

Monoctonus paulensis is a solitary parasitoid of several species of aphids, including the pea aphid, Acyrthosiphon pisum. We evaluated host-instar selection by comparing the parasitoid's preference for the four nymphal instars of the pea aphid, presented two at a time in dichotomous choice tests. Females parasitized more, and laid more eggs in, the relatively smaller aphids among those available. This preference was independent of aphid instar: L1 > L2 > L3 > L4. Preference was not influenced by female size or age. Normal and anaesthetized aphids were accepted equally. The total time needed by a female to capture, position, and parasitize an aphid varied among host instars, with fourth instars requiring nearly twice as much time as first, second, and third instars. The probability of an attacked aphid escaping or avoiding parasitism increased with aphid instar, from ~10% in first and second instars to ~50% in fourth instars. Although fourth-instar pea aphids contain more resources for offspring development than smaller counterparts, it may not be profitable for a female to invest opportunity time in attacks on large aphids.

Populations of the specialist gall-forming fly, Urophora cardui (Diptera: Tephritidae), were studied at the western and eastern margins of its distribution. In western Europe U. cardui attacks the creeping thistle Cirsium arvense, whereas in eastern Europe, in the Ural mountains, it attacks Cirsium setosum, a taxon closely related to C. arvense. Gall densities are high in the Ural mountains and can be predicted by environmental variables. Compared to galls on C. arvense, those on C. setosum are on average larger. This indicates better performance of U. cardui on C. setosum in terms of cell numbers per gall. Despite the wide distribution of U. cardui, the dominant parasitoids are the same at the western and eastern ends of its distribution and the interactions between parasitoids and the host are similar. In general, we suggest that the synchronisation between the host plant species, the phytophage and the parasitoids is an important factor in the spatial ecology and evolution of this food web.

The cixiid planthopper Hyalesthes obsoletus Signoret is an efficient vector of the stolbur phytoplasma, the cause of various crop diseases. In the field, this monovoltine species feeds on a wide variety of woody and herbaceous plants. It overwinters as larvae on the roots of its host plants. During this study, we collected adults mainly from lavender (Lavendula angustifolia Miller), bindweed (Convolvulus arvensis L. and C. sepium L.), hoary cress (Cardaria draba L.), and occasionally from plantain (Plantago cynops L.), toadflax (Linaria striata L.), bedstraw (Galium verum L.), and mountain savory (Satureia montana L.). Fertility of field collected females from sites at two different elevations differed significantly. Fertility at 300 m (50.6 eggs per female; N = 28) was more than twice that at 900 m (22.8 eggs per female; N = 19). Only one specimen of the species was found to be parasitized by an undetermined species of Dryinidae (Hymenoptera). H. obsoletus was reared in controlled conditions on lavender. Unlike in the field, larvae developed in the laboratory at the base of the host plant and on basal shoots. Egg incubation averaged 7 ± 1.2 weeks (N = 10). Total development time from egg to adult averaged 27 ± 4 weeks (N = 5) on lavender. A morphological description of the five instars is provided. The study was supplemented by scanning electron microscopy. Particular attention was paid to the structure of the wax-plates and the absence of compound eyes in the early larval stages.

Parasitised aphids often leave the aphid colony before mummification. It has been suggested that this behaviour is an example of host manipulation by the primary aphidiid parasitoid to reduce the risk of hyperparasitism after mummy formation. Mummification site and hyperparasitism risk are surveyed in 16 species of aphid. Mummification away from the colony was not associated with reduced hyperparasitism. In ant-attended species, and in species with well developed parasitoid defence behaviour (such as kicking), mummies formed within the colony tended to suffer less hyperparasitism. In laboratory experiments, two hymenopteran ectohyperparasitoids, Dendrocerus carpenteri (Curtis) (Megaspilidae) and Asaphes vulgaris (Walker) (Pteromalidae), were more successful attacking parasitised aphids [Uroleucon jaceae (L.) (Aphididae)] when the mummies were outside the colony, not surrounded by living aphids.

From 1994-1997 the food of Coccinella septempunctata L. was investigated on the basis of gut dissections of adults and larvae collected in the field. Additionally, the gut contents of adults fed under laboratory conditions were investigated. The likelihood of recovering different prey types during gut dissection was variable, which will be illustrated by presenting some common prey fragments. The food eaten by adult C. septempunctata throughout a year was studied at a locality in Berlin-Staaken. Ladybirds were collected from March 1994 until November 1997 in different crops and habitats on roughly a monthly basis. Aphid feeding was detectable from April until October. In May and June they were the most frequent food type. Fungal spores, in most cases the conidia of Alternaria spp., became most frequent in July. Additionally non-aphid arthropods were frequently preyed upon in July. A very common non-aphid prey item were thrips. Pollen was important in May and September. Comparing the food components of newly emerged adults with those of overwintered adults some remarkable differences were detected. In newly emerged adults non-aphid arthropods and fungal spores were much more frequent than in overwintered adults whereas aphids were less frequently found. The diet of adults and larvae was also investigated in June and July in cereal fields at two other localities, Northern Flaeming and Magdeburger Boerde. No difference in adult diet was found between the three localities. The composition of the larval diet was relatively similar to that of the adults.

Insect herbivores were collected from Castanopsis acuminatissima (Fagaceae) at Wau, Papua New Guinea, by beating the foliage of 15 trees during four one-month sampling periods, each representing different leaf-flush events. The association of leaf-chewing beetles with C. acuminatissima was verified with feeding trials. Of 59 species of leaf-chewing beetles that were collected, 36 species could be used in feeding trials. Only 9 of these species fed on C. acuminatissima. A further 27 beetle species were tested in feeding trials but did not feed. Of these, 7 were specialists feeding on other tree species within the surrounding vegetation. Most beetle species collected from C. acuminatissima foliage were probably transient species, dispersing from other tree species. Path analyses showed that herbivore abundance during a particular sampling period was significantly influenced by rainfall, leaf flush of other conspecific trees and air temperature, but not so by the species richness of surrounding vegetation, number of surrounding conspecific trees and size (DBH) of trees sampled. The species richness of leaf-chewing beetles collected on particular study trees depended on that of the surrounding vegetation, thus supporting the hypothesis that most beetle species collected were transient. The abundance of insect herbivores on particular C. acuminatissima trees probably depends on a balance between the leaf flush of conspecific trees and that of the particular tree sampled. The results also emphasize the need to remove transient species in analyses of insect faunas of tropical trees, at the risk of analyzing species richness patterns derived from loosely defined "assemblages" of species.

Two additional specimens of Canadaphis carpenteri Essig are described from amber in a primary site in Alberta, about 78 million years old. The rostrum is longer than previously supposed, and as siphuncular pores apparently are present, the family Canadaphididae is placed tentatively in the super-family Aphidoidea.

Aerial netting at a height of 150 m over West Bengal during November produced evidence for extensive nocturnal migrations of a number of insect taxa, including aphids, leafhoppers, Nilaparvata lugens (the brown planthopper) and Cyrtorhinus lividipennis (a mirid predator of plant- and leafhoppers). Preliminary trajectory analysis was undertaken for aphids (particularly Lipaphis erysimi) overflying the experimental site, and it was estimated from the timing and altitude of flight, and from the winds prevailing at the time, that the long-flying individuals may have originated from sources between 100 and 300 km away to the northeast.

Service M.W.: Mosquito Ecology. Field Sampling Methods. Elsevier Science Publishers Ltd., London & New York, 1993, 988 pp.

The head is traditionally considered to be the site of production and release of the egg development neurosecretory hormone (EDNH), involved in ovarian maturation in dipterans. We find, however, that the thorax and abdomen of the mosquito Aedes aegypti each possess factors which resemble EDNH in both physiological and biochemical properties. Extracts of thoraces or abdomens each stimulated the dose-dependent appearance of ecdysteroid in incubations of A. aegypti ovaries in vitro. In addition, each extract is capable of stimulating ovarian maturation in vivo in decapitated Aedes atropalpus. The head contains higher levels of activity, absolute and specific, than either the thorax or abdomen, but extracts of all three body portions yield similar chromatographic patterns of activity. Gonadotropic activity in all three extracts elutes in two molecular weight ranges, large (approx. 6,600-7,700 MW) and small (approx. 4,150-4,250 MW). In each tissue, the small molecular weight component is more active than the large component. The roles of these non-cerebral ecdysiotropins and gonadotropins are not clear, but their similarities to cerebral EDNH suggest a function in ovarian maturation.

An ecdysteroid receptor protein has been identified and characterized from whole body extracts of Chironomus thummi larvae. The kinetic and physical characteristics of this binding are consistent with the criteria established for steroid hormone receptors and are similar to those exhibited by the Drosophila ecdysteroid receptor. The binding data of cytosols obtained from different developmental stages (third and fourth stage larvae, pupae and adults) indicate only a single type of binding site which exists throughout the life cycle of the insect with an average K_d value of 5 × 10^-9 mol/g of protein. Furthermore, single point determinations of the receptor concentration at these stages revealed that the receptor level fluctuates. This fluctuation in the receptor level corresponds well to the fluctuation in the ecdysteroid titer indicating that the number of receptors at any particular stage of development may be regulated by the presence of the moulting hormone.

Lepidoptera populations were monitored during 29 years by a light-trap in urban Brno. Compared with other sites in the Czech Republic (Prague-Ruzynì, Èeské Budĕjovice, Černiš) urban Brno was extraordinarily rich in species, richer than the other Czech sites studied and richer than many British sites in an urban to natural gradient. Variability of the more common species at Brno was as high as that at the ruderal/deteriorated agricultural setting at Ceske Budejovice, and generally higher than that in the wet forest environment at Cernis and much higher than in the park-like/suburban/agricultural setting of Prague. Voltinism had no effect on variability from year to year. Most of the more common species in Brno clearly increased in abundance over the years, unlike those at the other sites. Much of the large diversity at Brno, however, was because of a large number of accidental species, vagrants from elsewhere. When considering only the more common species (>= 5 individuals per year), however, Brno is among the most species-poor sites. The common species at Brno were mostly tramp species that could take advantage of whatever food and habitat the city had to offer.

Because of strong correlations in abundance between species at one site with conspecifics at other sites over distances of 150-200 km, the abundances in these populations are apparently strongly affected by large-scale processes such as weather, overriding in part large differences between the habitats or by large-scale dispersal of individuals between sites. Significant correlations also existed between conspecifics in these sites in variability as well as in trends in time, with the curious exception of Cernis, the only reasonably natural habitat, suggesting that these parameters are strongly affected by local habitat characteristics.

Females of the aphid parasitoid Praon volucre were attracted to lures containing synthetic aphid sex pheromone components, particularly (+)-(4aS,7S,7aR)-nepetalactone, when these were placed on water traps in cereal fields in autumn. Trap catches were greatest at a site in S.W.England and fewest at sites in northern England 'and northern Germany, presumably due to climatic differences. Responses to the pheromones were not detected for any other cereal aphid parasitoids in the field trials, although Aphidius rhopalosiphi appears to possess olfactory receptors for (+)-(4aS,7S,7aR)-nepetalactone. A potential strategy for the use of aphid sex pheromone lures to manipulate aphid parasitoids in the field, in order to enhance their impact on aphid populations, is outlined.

Ten dominant heavy metals were analyzed in adults of the winter moth, Operophtera brumata (L.), from six sites in four isolated localities in South Bohemia. At all of the sites, metal concentrations conformed to the order Zn> Fe> Cu> Mn> Ni> Pb> Co> Cd> Cr> Hg. The highest concentration of toxic metals (lead and cadmium) was found in moths associated with trees along the main road in Plástovice (3.1 and 1.1 ppm, respectively), while it was lowest in the Èervené Blato peat bog (1.1 and 0.1 ppm, respectively). The main parasitoids were two tachinid flies, Cyzenis albicans Fall. and Phorocera obscura Fall., and one ichneumonid wasp, Agrypon flaveolatum Grav. Overall parasitism was low (2.8 and 5.9% in 1991 and 1992, respectively). The highest percentage of parasitism was on larvae in the unpolluted Èervené Blato bog (4.8 and 28.3% in 1991 and in 1992, respectively), and the lowest on apple trees along the main road in Plastovice, which was the most polluted site of the four localities.