Adult male German cockroaches were exposed to deposits of amorphous precipitated and pyrogenic silicas in continuous and discontinuous contact bioassays. LC50S of precipitated silicas in the former case generally increased with oil adsorption capacity of the dusts; variability in response in discontinuous contact bioassays was apparently due to grooming of appendages following pick-up of dust aggregates. The toxicity of silica deposits in half-treated choice boxes varied with relative humidity and was effectively eliminated at 95% r.h. or when free water was provided. Cockroaches accumulated in the untreated side of the box irrespective of r.h.; the mechanism of this effect is discussed.

Larvae of a flea-beetle, Chaetocnema arida, were found mining in the stems of young barley shoots in June 1939.

Chlorops pumilionis larvae infested barley most heavily in fields where Agriotes larvae were doing most damage. The Chlorops adults showed marked sexual dimorphism in both size and colour. The size range for this species is correlated with a proportionate size range in its parasites Coelinius niger and Stenomalus micans. Perforations 1·3 mm. in diameter in the top of a cage were sufficient for the escape of Stenomalus but not of Chlorops or Coelinius.

Lasiosina cinctipes larvae were commonly synoecious with Chlorops in barley shoots, but in some cases (5–10 per cent.) they were living without Chlorops. In these shoots the nodes were not swollen as in Chlorops infestation. Lasiosina was not attacked by the above parasites of Chlorops.

The larvae of Elachiptera cornuta infested shoots already badly damaged by other species and were accompanied by many Lasiosina larvae. Wet weather in July favours these two species. Their puparia differ in the form of the posterior spiracles. Elachiptera also occurred in maize and wheat.

Meromyza saltatrix var. nigriventris was present in stunted barley shoots in small numbers, producing swelling of the nodes very like that due to Chlorops. The summer pigmentation in both these species in Hampshire differed from that reported by Mesnil in France. Meromyza was also bred from wheat. Meromyza puparia, unlike those of Chlorops, were attached to barley sheathing-leaves by silk.

Oscinella frit larvae, infesting young sweet maize shoots at Gosden, Surrey, were either accompanied or followed by those of Aphanotrigonum trilineatum and Elachiptera. Infesting oat shoots at Long Sutton, Hampshire, Oscinella frit larvae were accompanied by larvae of Lasiosina and Camarota curvinervis. Adults of the latter emerged from stunted barley shoots in September. They showed some resemblance to flea beetles, possibly protective. Oscinella frit was also bred in small numbers from stunted wheat and barley shoots. The Chalcid, Callitula pyrrhogaster, was reared from pupae of this species found in oat shoots.

Larvae of a Muscid, Hylemyia (Phorbia) genitalis, infested a winter wheat crop in large numbers in May 1940. Tropidoscinis albipalpis, Oscinella? gracilior and Agromyza nigripes, were bred in small numbers from potted plants of this crop kept in a cage in the laboratory during the summer. Hylemyia genitalis and Agromyza (Domomyza) ambigua pupated in the soil surrounding the roots of these plants. The adults (together with a Braconxd parasite, Phaenocarpa pullata, Hal.) emerged from the soil in the following spring.

Comparisons of infestation and damage levels by the cotton bollworms, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), Earias vittella (Fabricius) and E. insulana (Boisduval) (Lepidoptera: Noctuidae) were made in cotton fields treated with pheromones + insecticide, insecticides only, and untreated control plots, in Pakistan during the 1991 cotton season. Early to mid season control of these three pests by mating disruption in the pheromone + insecticide treated plots meant that an average reduction of 3.5 applications of insecticides was achieved when compared with the insecticide only treated plots to control the cotton pest complex. Night observations showed that there were far fewer adult moths visible in the pheromone + insecticide treated plots than in insecticide only treated plots. Adults of both sexes were much less active and did not mate as frequently as adults in the insecticide only plots.

Diparopsis watersi (Roths.) is a serious pest of the cotton crop in the Gash Delta of the eastern Sudan. The climate and method of cotton cultivation are described briefly and a general account of the incidence of D. watersi during the season is given. Earlier work in the Sudan on this bollworm was mainly centred in the Northern Province and there is little information on the history of its occurrence in the Gash Delta. The aspects of its biology considered here include its egg-laying and larval habits, and duration of the pupal stage.

The majority of eggs were laid on the younger and more accessible plant growth. The period of wandering in search of food after eclosion from the egg was of short duration with normal egg placement, the emerging larvae had little difficulty in finding suitable food, and mortality from failure to do so was low on healthy plants. Depth of pupation did not vary greatly with soil type; the majority of pupae were found within one inch of the soil surface, and none at a depth greater than three inches. Only when the soil was a heavy clay that had baked hard following the rains, did the emerging moths have difficulty in passing through it and ascending to the surface.

The proportion of larvae forming diapause pupae increased amongst field-collected larvae as the season advanced, and in successive generations bred in an insectary from the non-diapause fractions of the preceding generations, but at no time was there a complete cessation in the production of non-diapause pupae and infestations persisted as long as there was actively growing cotton. This persistent activity in the Gash Delta is contrasted with the restriction of D. watersi to a six months' season in Nigeria. The emergence of moths from diapause pupae was not completed during the season following that of pupation, but extended for at least two further seasons; approximately 35 per cent, of the total diapause pupal population was still alive and present in the soil after the first season's emergence. In any one season the emergence was bimodal, the two peaks of emergence, which were of similar magnitude, occurring in September-October and mid-November to mid-January. When diapause pupae were kept in the laboratory and thus exposed to less extreme temperatures than in the field, the emergence was distinctly unimodal, with maximum emergence during September. The bimodal emergence observed in the field is considered to be a result of external environmental factors that inhibit pupal development at certain times of year, and emergence data from diapause pupae exposed to different climatic conditions suggest that high soil temperatures are such a factor. The pattern of moth emergence from diapause pupae in the Gash Delta is compared with that found in Nigeria and Nyasaland.

Natural mortality of D. watersi is discussed, and certain larval parasites, notably an un-named species of Apanteles of the ultor Reinh. group, and Bracon brevicornis Wesm., are considered to be of importance.

The study of the biology of D. watersi has emphasised the difficulties in controlling this bollworm, and stressed the importance of attempting to destroy it in the diapause state, preferably during the “ dead ” season. It is considered that mechanical cultivation, of the soil may provide a means to that end.

Single applications of slow-release pheromone formulations were used to control yellow stem borer, Scirpophaga incertulas Walker, by mating disruption in two trials on rice in India. The first trial compared the efficacy of two formulations containing 1:10:1 and 1:10:0 ratios of (Z)-9-hexadecenal, (Z)-ll-hexadecenal and (Z)-9-octadecenal, components of the S. incertulas pheromone, and a commercially-available formulation, Selibate CS, containing the related Chilo suppressalis Walker pheromone, a 1:10:1 blend of (Z)-9-hexadecenal, (Z)-ll-hexadecenal and (Z)-13-octadecenal, with farmers' practice plots treated with insecticides. Pheromone trap catches indicated that in each of the pheromone-treated plots the catches of male moths were reduced by up to 98% compared with catches in the insecticide-treated plots suggesting that pheromone-mediated communication was disrupted. Larval damage ranged from 5.7 to 8.1% white heads (WH) in the insecticide-treated plots compared to a significantly reduced range of 2.1 to 2.4% WH in the pheromone-treated plots. There was no significant difference between the damage estimates recorded for each of the different pheromone treatments. A second trial compared the effect on efficacy of applying the two-component pheromone formulation on different dates, 9–12 and 39–44 days after transplanting. Both pheromone treatments gave significantly lower levels of WH damage compared to equivalent insecticide treated plots; 1.8, 2.0, and 6% respectively. In both trials rice grain yields increased by between 5 and 12% in pheromone-treated plots compared to insecticide treated plots, which was due, at least in part, to the cumulative effect of reduced stem borer damage in both the tillering and reproductive stages of the crop cycle. The formulations exhibited pseudo-zero order release rates with field lives of between 70 and 90 days.

In southern Brazil, adults and larvae of the halticine beetle Alagoasa parana Samuelson fed on the foliage and flowers of Lantana tiliaefolia and L. glutinosa (Verbenaceae). The life-cycle of this univoltine species from egg to adult emergence took 80-90 days between October and April. The abundance varied seasonally from four to eight adults per 100 branches. Larvae remained on the foliage during development and pupated in moist, loose, friable soil within a cocoon at the base of the host-plant. Adults overwintered and oviposited in litter at the base of the host-plant. In multiple-choice host- specificity studies in Australia, adults fed lightly on Verbena bonariensis and Clerodendrum speciosissimum (Verbenaceae) and produced minute scars on leaves on unrelated passion fruit (Passiflora edulis) and sunflower (Helianthus annuus). However, A. parana completed immature development only on L. camara among the 55 plants tested. The potential of A. parana as a biological control agent for L. camara in Australia is discussed.

We investigated the effects of the antiparasitic drug ivermectin on the dung beetles Copris acutidens Motschulsky, Onthophagus bivertex Heyden, O. lenzii Harold and Phelotrupes auratus auratus Motschulsky in Japan. Ivermectin was detected in cattle dung from 1 to 3 or 7 days post-treatment, with a peak at 3 days post-treatment in two pour-on administrations (500 µg kg−1). In C. acutidens, adult survivals and numbers of brood balls were significantly reduced in dung collected at 3 and 7 days post-treatment, and adult emergence rates were significantly decreased in dung collected at 7 and 14 days post-treatment. Feeding activity of C. acutidens was inhibited in dung collected at 3 days post-treatment, but was not significantly different from that seen in control dung at 7 and 14 days post-treatment. In O. bivertex and O. lenzii, there were no effects of ivermectin on adult survival or feeding activities, but the numbers of brood balls of O. bivertex constructed in dung collected at 3 and 7 days post-treatment were significantly lower than observed with control dung. The adult emergence rates of O. bivertex and O. lenzii were significantly reduced in dung collected at 1 to 3 and 1 to 7 days post-treatment, respectively. In P. auratus, there were no effects of ivermectin on adult survival, oviposition, feeding activity, or larval survival (until the third instar) in dung at 3 days post-treatment. The environmental risks affecting the populations of dung beetles in Japan are discussed.

There are three main parasitoids and one very efficient predator associated with Perrisia pyri in France. Of these, at least during July and August, the predacious Capsid, Pilophorus perplexus, achieves the greatest destruction of midge larvae.

The two species of Platygasterids differ in several points of ethology from the species of the same or adjacent genera attacking Contarinia pyrivora. They are both egg-parasites, developing very slowly in the midge larvae during the growth of the host. Their action appears to be largely complementary, corresponding to morphological differences in the organs of oviposition. Their life-history is very imperfectly known.

Torymus abbreviatus is extremely efficient. Its eggs are laid within the curled leaf among well-grown midge maggots on which the larva lives as an ectoparasitoid. The duration and location of the pupa stadium is unfortunately not yet known.

Some half a dozen other enemies were found to play a less important part than the preceding.

Natural enemies that respond to prey in a density-dependent manner may be able to quickly suppress pest populations before they reach economically damaging levels. Although it is primarily the combination of a natural enemy's functional response and a population numerical response that will influence the maximum number of pests attacked, other factors may influence a density-dependent response. We conducted large-scale field experiments, both artificially inoculating grapevines with larvae and using naturally occurring populations, to quantify and characterize the response of a parasitoid, Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) to different densities of its host, the pest of grapevines, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). We showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that the degree of parasitism was consistently and significantly higher in the grape variety Cabernet Sauvignon compared with Chardonnay. While the significant effect of variety on the degree of parasitism may provide an option for increasing the parasitism of E. postvittana by D. tasmanica, it also highlights how differences in host plant can influence trophic interactions.

In the Western Himalayas, Drosophila nepalensis is more abundant during the colder and drier winter than the warmer rainy season but the mechanistic bases of such adaptations are largely unknown. We tested effects of developmental plasticity on desiccation-related traits (body size, body melanization and water balance traits) that may be consistent with changes in seasonal abundance of this species. D. nepalensis grown at 15°C has shown twofold higher body size, greater melanization (∼15-fold), higher desiccation resistance (∼55 h), hemolymph as well as carbohydrate content (twofold higher) as compared with corresponding values at 25°C. Water loss before succumbing to death was much higher (∼16%) at 15°C than 25°C. Developmental plastic effects on body size are associated with changes in water balance-related traits (bulk water, hemolymph and dehydration tolerance). The role of body melanization was evident from the analysis of assorted darker and lighter flies (from a mass culture of D. nepalensis reared at 21°C) which lacked differences in dry mass but showed differences in desiccation survival hours and rate of water loss. For adult acclimation, we found a slight increase in desiccation resistance of flies reared at lower growth temperature, whereas in flies reared at 25°C such a response was lacking. In D. nepalensis, greater developmental plasticity is consistent with its contrasting levels of seasonal abundance. Finally, in the context of global climate change in the Western Himalayas, D. nepalensis seems vulnerable in the warmer season due to lower adult as well as developmental acclimation potential at higher growth temperature (25°C).

It is estimated that in 1953, as a result of attack by Wheat Bulb Fly, Leptohylemyia coarctata (Fall.), 59,000 acres of wheat were re-drilled and 58,000 acres were patched with spring-sown wheat; another 85,000 acres were affected without any action being taken by the farmer. The cost of new seed and the reduction of yield of spring wheat as compared with winter wheat represent a minimum financial loss of about £1,200,000. With the aid of maps it is shown that the distribution of damage is similar to the distribution of wheat and to the area with less than 30 in., rainfall annually. In districts where over 5 per cent. of the combined crops and grass acreage is in potatoes, there is a tendency for the amount of damage by Wheat Bulb Fly to increase with increasing potato acreage.

It is tentatively suggested on circumstantial evidence that high rainfall on the west side of the country is partly responsible for the absence there of damage by Wheat Bulb Fly. Many of the variations in the distribution of damage on the eastern side of the country could be accounted for by differences in cropping.

In Scotland, the distribution of the fly is also confined to the eastern side. There are a few records of the fly in the Republic of Ireland.

Studies are reported on the extent and importance of competition amongst larval and pupal parasites of Oscinella frit.

In Ontario, 30–40 per cent. of frit larvae are parasitised by Hexacola in July–August and superparasitism is thus likely. Subsequent attack by Polyscelis may occur, but probably unsuccessfully.

Competition between the larval parasites and the pupal ecto-parasites Callitula and Spalangia is generally slight, because the former species is not abundant and the latter tends to select only healthy hosts.

Experiments are described to test the inter-relations of the three pupal parasites by exposing puparia of Drosophila melanogaster to two species simultaneously and in sequence.

When Callitula and Spalangia are allowed to oviposit simultaneously, the former is more successful when hosts are relatively few, but otherwise the two species are equally successful. When Callitula parasitises puparia recently exposed to Spalangia, equal numbers of the two parasites emerge, but in the reverse experiment Callitula is superior. Callitula is able to parasitise successfully a proportion of puparia already containing Spalangia whatever the age of the latter; mature Spalangia thus attacked are mostly killed.

Similar comparisons of Callitula and Spalangia with the endoparasitic Loxotropa show that Loxotropa is inferior to both the others, but that all three show marked avoidance of multiple parasitism.

In general, there is little interference between the various species in the parasite complex associated with the frit-fly.

The parasite complex associated with the frit-fly appears to be one that is very well balanced, there being little interference between the various species involved. Moreover, when, for any reason, one species does not attain its accustomed degree of parasitism, this is offset by an increase in the numbers of one or more of the other species.

Cross-mating experiments are reported between adults of the typical, darkclubbed form of Syntomosphyrum glossinae Wtstn., obtained from pupae of Glossina pallidipes Aust. from Kenya and of G. palpalis (R.-D.) and G. morsitans submorsitans Newst. from Northern Nigeria, and the ‘white-clubbed’ form of Syntomosphyrum, originally reported by Waterston from Nyasaland, obtained from pupae of G. morsitans Westw. from Tanganyika.

Fertilised eggs, giving rise to offspring of both sexes, were produced only by crosses between the strains of typical S. glossinae. Crosses in either direction between the ‘white-clubbed’ form and typical S. glossinae resulted in all-male progeny, presumed to develop from unfertilised eggs. It is considered that this is evidence of a physiological barrier to reproduction between the two forms. The ‘white-clubbed’ form is therefore regarded as a distinct species.

Pteronidea ribesii, Scop., the common gooseberry sawfly, is widely distributed in Middle and Northern Europe and in North America, and appears to be confined to food-plants of the genus Ribes, particularly R. grossularia and R. rubrum. It has an extensive literature, one of the best and most recent accounts being that of Kemner (1924). In the present account, therefore, only a summary of the author's investigations are given, with emphasis on points of special interest or significance in relation to the present series of studies.

It is an early experience of the Field Entomologist in the Tropics, whether his work lies in countries such as the East African Protectorates, which have well defined seasons, or where the seasons are less clearly marked, as in the Federated Malay States, that a seasonal prevalence of the commoner insects is quite as definite as it is in the Temperate regions. Outside the Tropics the main factor determining prevalence would seem to be suitability of temperature, but in the Tropics, where temperature variations may be slight, moisture is the controlling factor. Purely terrestrial insects which feed, whether as larvae or imagos wholly on vegetable material, breed and are most abundant at such times as the food-plants are at their best, that is when, as the result of favourable conditions of temperature and moisture, there is a full flow of tissue-building sap. The law of seasonal prevalence is valid also for many insects whose imagos derive their food directly from the larger animals, a source of supply available at all seasons. For these insects, too, the same conditions hold good, but affect chiefly the larvae.

Shin Etsu twist-tie ropes containing the spiny bollworm (Earias insulana(Boisduval)) pheromone were tested for mating disruption in a cotton field in Israel during 1991. Two applications of the Shin Etsu rope formulation (1000 ropes/ha), containing 50 mg pheromone per rope, effectively disrupted mating of E. insulana, reduced damage to cotton bolls, and minimized the number of chemical treatments needed. The success of the mating disruption, which lasted for more than 3.5 months, was indicated by the following: 1. Reduction of trap catches in the pheromone-treated plot as compared with the control plot (commercially treated with insecticides). 2. Lower infestation of cotton bolls in the pheromone-treated as compared with the control plot. 3. Over 90% reduction in mating success in the pheromone-treated plot, as indicated by the number of mating pairs collected at night in the two plots. 4. Reduced number of insecticidal treatments applied in the pheromone-treated plot. The release rate of the pheromones was monitored by periodical gas chromatography analyses of the remaining pheromone in ropes. The half lives of the E. insulana and Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) formulations were similar, with t1/2=45-60 days. In Israel, E. insulana and P. gossypiella infest cotton fields almost simultaneously and are controlled by the same insecticides. Therefore, the control of E. insulana with pheromones is essential in order to give reasonable meaning to the commercial application of pheromones for the control of P. gossypiella, as is practised today in many cotton fields. The present study indicates that control of E. insulana by the mating disruption technique is viable.

In both experimental and naturally developed colonies, Aphis fabae Scop., and Acyrthosiphon pisum (Harris) were concentrated on the upper parts of broad bean plants. A. pisum resembled Myzus persicae (Sulz.) rather than Aphis fabae by normally infesting leaves, not stems. Colonies of M. persicae were dispersed over the whole plant. In laboratory experiments, apterous adult aphids were observed walking on bean plants, and their activity was recorded in terms of their actions at each node. Moving aphids of both species tended to maintain their direction at a node although the structure of the plant does not appear to favour this. Aphids of both species changed their direction of movement more often after going onto the leaf at a node than when they stayed on the stem. M. persicae adults went upwards as often as they went down, but those of Acyrthosiphon pisum walked up more often than down and were more likely to turn round if they were moving downwards. These differences in the behaviour of active individuals would tend to produce the differences between the observed spatial distributions of the two species, although other factors, including leaf age and reproductive rates are probably more important in determining the form of aphid colonies.

Female oriental armyworm moths, Mythimna separata (Walker), emerged without discernible oocytes in the ovarioles, and reproductive maturity, on the criterion of onset of calling behaviour, was associated with an intermediate stage of oocyte development. Ingestion of carbohydrate was required for completion of oocyte development in the majority of females although a proportion matured when allowed only water. Among females kept alone, these were exclusively moths from a strain selected for early onset of calling but, in the presence of a male, a few females from an unselected line also called and achieved oocyte maturation, without access to carbohydrate. Thus factors other than ovarian development apparently influence the commencement of calling. The absence of an effect of carbohydrate uptake on pre-calling period supports a previous conclusion that this trait is determined primarily by genetic components in this species. It is concluded that ingestion of carbohydrate is important for the attainment of reproductive maturity in M. separata but that it has a differential effect in early and later-calling genotypes. The implications of the results for the reproductive and migratory strategies of M. separata, an important agricultural pest, are discussed.

The species for which this genus is proposed is closely allied to Polydrusus, Germ., and agrees with it in all its more salient characteristics; but it differs from all the species of that genus known to me in the following points:—The head bears a long, deep median furrow; the epistome forms a large bare smooth triangular area, which is well defined and in no way impressed, but even slightly convex; the elytra have a prominent posterior callus, and the ninth and tenth striae coalesce in the middle for one-third of their length.