The following report is based on a tour which extended from September 1915 to February 1917, but included in it are also some observations made during a few months residence in 1914.

The area comprised lies partly in the Northern Territories of the Gold Coast, and partly in Togoland (see Map, Bull. Ent. Res., V, p. 32). It extends from 8° N. to 9° 45' N. and from 0° 15' E. to 2° 30' W. My headquarters were at Yapi on the River Volta about 28 miles south-west of Tamale, the capital of the Northern Territories. I have already described in a previous report the nature of the country and the type of vegetation, so need not repeat them here. I examined the whole of the Volta from Yapi to Yeji by canoe, and then followed a sinuous route on my return journey, keeping as close to the River as possible. The country between Yapi and Daboya, a large town with an important ferry on the Volta, was traversed on several occasions. From Daboya I went to Bole and made my temporary headquarters at Larabanga, the centre of the game and Glossina submorsitans area. Here I spent several weeks under canvas in three separate localities in the bush. On my homeward journey I visited Yendi, formerly an important German post in Togoland, thence going to Salaga and Kete-Krachi, where I crossed the Volta and proceeded to join the main north road at Atabubu (Tabobo).

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.

We examined the role of the most important metabolic enzyme families in the detoxification of neurotoxic insecticides on adult males and females from susceptible populations of Cydia pomonella (L.), Grapholita molesta (Busck), and Lobesia botrana (Denis & Schiffermüller). The interaction between the enzyme families – carboxylesterases (EST), glutathione-S-transferases (GST), and polysubstrate monooxygenases (PSMO) – with the insecticides – chlorpyrifos, λ-cyhalothrin, and thiacloprid – was studied. Insect mortality arising from the insecticides, with the application of enzyme inhibitors – S,S,S-tributyl phosphorotrithioate (DEF), diethyl maleate (DEM), and piperonyl butoxide (PBO) – was first determined. The inhibitors' influence on EST, GST, and PSMO activity was quantified. EST and PSMO (the phase-I enzymatic activities) were involved in the insecticide detoxification in the three species for both sexes, highlighting the role of EST, whereas GST (phase-II enzymes) was involved only in G. molesta insecticide detoxification. L. botrana exhibited, in general, the highest level of enzymatic activity, with a significantly higher EST activity compared with the other species. It was the only species with differences in the response between sexes, with higher GST and PSMO activity in females than in males, which can be explained as the lower susceptibility of the females to the tested insecticides. A positive correlation between PSMO activity and the thiacloprid LD50s in the different species-sex groups was observed explaining the species-specific differences in susceptibility to the product reported in a previous study.

Pheromones play an important role in mediating interspecific interactions in insects. In an insect community, pheromones can reveal information about the senders, which could be used by other members of the food web (competitor, natural enemies, etc.) to their own advantage. The aggregation pheromones of two closely related thrips species, Frankliniella occidentalis and Frankliniella intonsa, have been identified with the same major compounds, (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, but in different ratios. However, the roles of the aggregation pheromones in the interspecific interactions between these two closely related species are unknown. Here, we investigated the roles of major aggregation pheromone compounds in interspecific interactions between F. occidentalis and F. intonsa for both long and short ranges. The results showed that, at tested doses, neither aggregation pheromone-induced long range cross-attraction nor short range cross-mating was detected between F. occidentalis and F. intonsa. Field-trapping trials showed that the species-specificity in aggregation pheromones was regulated by the ratio of two major compounds. However, species-specific blends of the two major compounds had no effect on short-range interactions between these two species. Our data from the thrips species provide support for the ‘aggregation model of coexistence’, explaining the species-specific pheromone-mediated coexistence of closely related species. Thus, species-specific pheromones could be one of the factors affecting population dynamics and community structure in closely related insects with similar niches.

Some bark beetle species (Coleoptera: Scolytinae) produce aggregation pheromones that allow coordinated attack on their conifer hosts. As a new saproxylic habitat is founded, an assemblage of associated beetles kairomonally respond to bark beetle infochemicals. Ips sexdentatus is one of the major damaging insects of Pinus spp. in Southern Europe. Its response to varying ipsenol (Ie) percentages in relation to ipsdienol (Id) was studied in northwestern Spain, along with the entire saproxylic beetle assemblage captured at multiple-funnel traps. Response profile modeling was undertaken for I.sexdentatus sexes and sex-ratios, associated species and for selected trophic groups using a reference Gaussian model. In addition, the effects on the saproxylic assemblages were analyzed. I. sexdentatus response curve peaked at 22.7% Ie content, while remaining taxa that could be modeled, peaked above ca. 40% Ie. Predator guilds showed a linear relationship with Ie proportion, while competitors showed a delayed response peak. Consequently, species assemblages differed markedly between varying pheromone component mixtures. Given that the evaluated pheromonal proportions mimicked that of logs being colonized by I. sexdentatus, results suggested that the registered differential responses at different levels might provide I.sexdentatus with a temporal window that maximizes conspecific attraction while reducing interference with competitor and predatory guilds. Described responses might help improve the monitoring of the population status of target bark beetles and their associates, but also point toward the by-catch of many natural enemies, as well as rare saproxylic beetle species, interfering with the aims of sustainable forest management.

Plant-sucking stinkbugs are especially associated with mutualistic gut bacterial symbionts. Here, we explored the symbiotic relationship of a pistachio stinkbug, Acrosternum heegeri Fieber by histological, fluorescence in situ hybridization (FISH), real-time PCR and molecular phylogenetic techniques. Furthermore, the effects of the symbiont on the resting/wandering behaviors of the newborn nymphs, pre-adult survival rates, and stage compositions were investigated. Transmission electron microscopy and real-time PCR analyses showed that a rod-shaped gammaproteobacterium was persistently located within the posterior midgut crypts. Molecular phylogenetic and FISH techniques strongly suggested that this symbiont should be placed in the genus Pantoea of the Enterobacteriales. Scanning electron microscopy confirmed the presence of the bacterial cells on the egg surface which the surface sterilization of the eggs resulted in the successful removal of the symbiont from the eggs. Symbiotic and aposymbiotic A. heegeri showed no significant differences in the wandering behaviors of the first nymphal stages, while the symbiont-free insects suffered retarded growth and lower survivability. Together, the results highlight the habitat and acquisition features of Pantoea symbiont and its contribution in A. heegeri biology that might help us for better pest management in the future.

The weights of insecticide picked up by mosquitos and tsetse flies in short contact periods on deposits from aqueous suspensions of DDT crystals of different sizes have been determined chemically and correlated with corresponding mortality rates.

The rate of action of DDT particles picked up by mosquitos increases as the size decreases.

Taking into account the weights of insecticide picked up, the median lethal dosage increases as the particle size increases. A further factor, that of retention on the body of the insects, has to be considered, however, for there is evidence that adherence of particles in the 0–10 and 10–20 micron ranges is greater than that of larger particles. Availability, and therefore effectiveness, of deposits from aqueous suspensions of insecticide particles is influenced considerably by the type of material to which they are applied.

Experiments were conducted to ascertain whether the rearing density of Dysdercus fasciatus Sign. affected its rate of development, colour, size, reproduction and general activity. The length of the nymphal and adult life decreased when more than 12 insects were reared per 200-cc. cage. Isolated virgin females and females that eopulated once lived longer than females each kept constantly with one male. Nymphal crowding in adults that were smaller than those reared in isolation and in an excess of males. Nympha derived from crowded parents became red at an earlier age than the progeny of one male and one female per cage. Crowding reduced feeundity when the density of nymphs or adults, either male or female, was increased.

The pre-oviposition period and the time interval between successive egg-batches were greater for virgin than for mated females. Infertile eggs were the longest; females allowed to copulate once laid eggs intermediate in size between infertile ones and those laid by females each kept with a male. The number of eggs laid by females isolated throughout life with one male was found to be higher than the number laid by those that were crowded either in the nymphal stages or were crowded with males in the adult stage. When Dysdercu8 was crowded with one or two locusts the number of eggs laid and the number of egg-batches were considerably reduced; amputation or painting the antennae, which caused the Dysdercus to be less active, also reduced egg production but disturbance by mechanical shaking of the container had little effect. These findings are discussed in relation to the ' phases ' of locusts and other insects, and it is concluded that the effects of crowding on D. fasciatus do not completely parallel phase differences in locusts.

The effect of temperature on the rate of consumption of the lipid reserves in Ixodes ricinus Linnaeus was characterized in constant temperature experiments. There was a consistent linear relationship between temperature and lipid consumption in nymphs and adult females and males between 5 and 37°C. Nymphs and adults were able to withstand extended periods of exposure to temperatures within the range of 2–37°C, although at 2°C there was evidence of thermal stress. The variance about the median rate of lipid consumption was found to increase with increasing rate of lipid consumption. Predictions of longevity were made using the rates of lipid consumption for the three stages studied, which ranged from 16 weeks to more than two years depending on temperature and stage. The predictions were consistent with reported survival times for I. ricinus and followed patterns reported for other ixodid ticks.

Life tables were developed to assess the significance of natural enemies on the dynamics of apple ermine moth, Yponomeuta malinellus Zeller, in southwestern Germany and to select parasitoid species for use in the biological control of this pest in Canada. During the study from 1993 to 1995 the abundance of Y. malinellus varied from 1.5 to 4.3 tents per 100 leaf clusters indicating that this was a non-outbreak population. From the life tables it was evident that the impact of egg predators accounted for 25–43% of the total generational mortality of Y. malinellus, more than any other known mortality factor. Percent parasitism varied from 18 to 30%, but the impact of parasitoids in relation to the total generational mortality of Y. malinellus from the life tables was remarkably constant at 11–14%. The loss of potential fecundity had an important influence on the generational mortality of Y. malinellus, but declined from 27% to 15% over the course of this study. This decline corresponded with a rise in the net rate of increase R0 from 1.35 in 1993 to 6.8 in 1995, despite the impact of insect predators and parasitoids on the generational mortality. Yponomeuta malinellus was attacked by five different obligate primary parasitoids, a single obligate hyperparasitoid, and three facultative hyperparasitoids. Of these, the oligophagous egg-larval parasitoid Ageniaspis fuscicollis Dalman (Encyrtidae) and the oligophagous larval-pupal and pupal parasitoid Herpestomus brunnicornis Gravenhorst (Ichneumonidae) were selected as potential biological control agents for Canada due to a minimal degree of interspecific competition.

Culicoides imicola is the main vector for bluetongue (BT) and African horse sickness (AHS) viruses in the Mediterranean basin and in southern Europe. In this study, we analysed partial mitochondrial cytochrome c oxidase subunit I (COI) gene to characterize and confirm population expansion of Culicoides imicola across Spain. The data were analysed at two hierarchical levels to test the relationship between C. imicola haplotypes in Spain (n=215 from 58 different locations) and worldwide (n=277). We found nineteen different haplotypes within the Spanish population, including 11 new haplotypes. No matrilineal subdivision was found within the Spanish population, while western and eastern Mediterranean C. imicola populations were very structured. These findings were further supported by median networks and mismatch haplotype distributions. Median networks demonstrated that the haplotypes we observed in the western Mediterranean region were closely related with one another, creating a clear star-like phylogeny separated only by a single mutation from eastern haplotypes. The two, genetically distinct, sources of C. imicola in the Mediterranean basin, thus, were confirmed. This type of star-like population structure centred around the most frequent haplotype is best explained by rapid expansion. Furthermore, the proposed northern expansion was also supported by the statistically negative Tajima's D and Fu's Fs values, as well as predicted mismatch distributions of sudden and spatially expanding populations. Our results thus indicated that C. imicola population expansion was a rapid and recent phenomenon.

Density-specific sampling plans were developed under African conditions for the exotic spider mite, Mononychellus tanajoa (Bondar), a serious pest of cassava, Manihot esculenta. The within-plant distribution of Mononychellus tanajoa was found to favour new foliage, regardless of time of planting or plant age. Consequently, the first developed leaf near the top of the foliage was selected as the sampling unit and related to whole plant populations of M. tanajoa. The relationship between the mite population's variance and mean as measured by Taylor's Power Law proved to be stable over a range of planting dates, seasons and locations. Two binomial sampling plans, one based on Taylor's dispersion parameters and another based on direct field observations, were developed and compared. Binomial sampling, appropriate only for densities below 30 mites per leaf, was replaced by an enumerative procedure based on a ‘quick count’ protocol at higher mite densities.

The insect cuticle is covered by a thin layer of hydrocarbons not only preventing desiccation but also playing an important role in the sexual communication of several species. In the pteromalid wasp Lariophagus distinguendus, a parasitoid of grain infesting beetles, female cuticular hydrocarbons (CHCs) elicit male courtship behaviour. We analyzed the CHC profiles of male and female L. distinguendus wasps reared on different beetle hosts by coupled gas chromatography- mass spectrometry (GC-MS). Statistical analysis of the data revealed significant differences between strains reared on different hosts, while spatially isolated strains reared on the same host produced similar profiles. CHC profiles of parasitoids reared on Stegobium paniceum were statistically distinguishable from those of wasps reared on all other hosts. A host shift from Sitophilus granarius to S. paniceum resulted in distinguishable CHC profiles of L. distinguendus females after only one generation. Considering the role of CHCs as contact sex pheromones, our data suggest that host shifts in parasitic wasps might lead to reproductive isolation of host races due to the modification of the cuticular semiochemistry.

Many female Anophelines wander into huts at random, possibly for shelter, and afterwards feed upon any suitable inhabitants.

This random wandering can be eliminated by pyrethrum spraying, and the acute discrimination of those Anophelines which enter primarily for food can then be demonstrated.

In sprayed huts there was a close relation between the number of men sleeping and the number of Anophelines attracted. The proportions attracted by 3 men and by 1 man were, for A. melas, 2·72; 1: A. gambiae, 2·38; 1: A. funestus, 2·28; 1. Discrimination was reduced at one period by the masking odour of cut and withering bush.

There were marked fluctuations in the attractiveness of individuals to Anophelines. On several occasions one or other of the men used as bait suddenly became much more attractive than his fellows, and remained so for several days.

The removal of a village increased by only 25–50 per cent. the proportion of mosquitos caught in two huts which were allowed to remain on the village site. This result indicates that most of the mosquitos which had infested the village had been attracted from a distance by the scent, and had not merely arrived in the vicinity of the village by chance.

An estimate of the inbreeding coefficient, FIS, of the coffee berry borer, Hypothenemus hampei Ferrari, was calculated from genotype frequencies of endosulfan resistance in beetles collected from berries in 41 different fields on the East Coast of New Caledonia. Two different estimates were obtained as a function of sampling date: FIS=0.491 ± 0.059 (s.e.) for samples collected in September, and FIS=0.215 ± 0.108 for samples collected in April. These values of FIS are very high in comparison to those of most insects, but surprisingly low given current understandings of H. hampei mating patterns. The difference between April and September FIS estimates is discussed in terms of insecticide regimes and seasonal variability of sib inbreeding levels. The high level of inbreeding in the coffee berry borer increases frequencies of homozygotes relative to heterozygotes. Inbreeding will accelerate resistance evolution whenever the fitness of homozygous resistant insects exceeds that of heterozygotes, and will undermine any high-dose strategy to control resistance evolution.

In laboratory experiments, all stages of the Egyptian cotton-leaf worm (Spodoptera littoralis (Boisd.)) were killed by exposure at 1–2%C for ten days, but the peach-potato aphid (Myzus persicae (Sulz.)) and the red spider mite (Tetranychus urticae (Koch)) were not controlled by this treatment. When exposed to methyl bromide, all the S. littoralis eggs tested were killed by a concentration × time product (CTP) of 44 mg h/litre at 18%C, but control of all stages of M. persicae and T. urticae required a CTP of at least 88 mg h/litre.

The present paper is a part of the results of my revisional work on the group Cyrtacanthacrini, which includes all the swarming locusts except Locusta migratoria (L.), the latter having formed the subject of a previous paper. The revision itself, being of a purely systematic character and dealing also with a large number of species of no economic interest, is being published elsewhere, but I thought it might be useful to economic entomologists to give here the principal conclusions arrived at concerning the species of known agricultural importance, especially because this presents an opportunity of discussing some important points in the bionomics of swarming locusts which would be out of place in the revision itself.

The biology of N. hololeucus, T. globulus, G. psylloides, S. squamosum and E. hilleri has been studied to estimate their potentialities as pests of stored products.

They are widely distributed and feed on a very wide range of foodstuffs of both plant and animal origin.

Adult life is usually longer than the development period. Oviposition extends over most of the adult life. In warehouses all stages of development are present together.

At 70 per cent. R.H. the developmental period (egg laid to emergence of adult from its cocoon) comprises: 12 to 21 per cent. as the egg stage, 52 to 70 per cent. as larva, 12 to 16 per cent. as pupa and 6 to 19 per centg. as adult in cocoon.

The mean lengths of the various developmental stages, including the larval instars, have been found under several sets of physical conditions.

Llaveia abrahami, sp. nov.

Female, adult. Ovate, strongly gibbose above and flattened beneath; segmentation both on the dorsum and venter distinct. Colour, in alcohol, buff-yellow; with a thin deposit of white secretion in the hollows between the segments; legs and antennae yellowish brown. It is highly probable that much of the secretion had disappeared in the alcohol in which the specimens were preserved. Antennae of eleven segments, 2nd and 11th longest; 3rd a little shorter than the latter, but much longer than the succeeding ones, which are submoniliform in shape; average length 0·8–0·9 mm. Legs relatively short; tarsi a little more than half the length of the tibiae; front pair shortest, measuring 0·85 mm.; posterior pair longer, measuring 1–1·1 mm.; hairs relatively long and slender; claws simple, though in one example two of these organs have a well-marked tooth-like projection dorsally, just above the curved tip. Derm both dorsally and ventrally rather thickly set with very short fine hairs; margin with a narrow band of long fine hairs, the longest of which measure 0·6–0·7 mm. Pores dorso-ventrally relatively very small, circular and with beaded rims; these are less numerous than the fine hairs; those at the margins are slightly larger, much more numerous, and many have clear triangular-shaped centres. Anal segment of abdomen with three large ovate rings, the central one being slightly the largest and measuring about 0·2 mm. in its longest axis. Length, after maceration in KOH, 8–9 mm.

A brief historical account is given of the spread of the Eucalyptus Snout Beetle, Gonipterus scutellatus Gyll., fron Australia, its country of origin, and of the utilisation of its natural parasite Anaphoidea nitens Gir. for its control on the African mainland.

The discovery of G. scutellatus in Mauritius is described. Its entry was effected between 1935–40, and by 1944 it was threatening Eucalyptus plantations over the whole island.

A. nitens was introduced in 1946 from East Africa. Establishment was extremely rapid and two years later G. scutellatus was effectively controlled.

Notes are given on the bionomics of both host and parasite under Mauritian conditions.

Ecological data are briefly discussed.