Analysis of published data on catches of insects in light-traps with a variety of light sources and of different designs showed that all conformed to the previously proposed model describing the functioning of a light-trap: catch = constant × where W = trap illumination and I = background illumination. Light-trap catches in differing cloud conditions and in open and woodland situations also varied as predicted by the model. A table of correction factors for different amounts of cloud cover is provided. The results are discussed in relation to use of light-traps and interpretation of light-trap data.

Based on the results of field surveys carried out between May 1977 and June 1981, the distributions of Glossina morsitans submorsitans Newst., G. palpalis gambiensis Vanderplank and G. tachinoides Westw. in Mali are presented and compared with previously reported information. The distributions of both G. m. submorsitans and G. p. gambiensis were found to be greater than previously reported, whereas that of G. tachinoides was found to be less. The apparent northern limits of both G. m. submorsitans and G. p. gambiensis are at approximately 14°20′N but that of G. tachinoides is at only about 13°10′N. No specimens of G. longipalpis Wied., previously reported from Mali, were captured.

Bracon ?hancocki (Wlkn.) is a larval ectoparasite of Cydia ptychora (Meyr.), a major pest of cowpea at Ile-Ife, Nigeria. Parasitism occurred in the field all the year round, varying from 0 to 65·9% and with the highest incidence from September to February. In the laboratory, the fecundity of the parasite was low, averaging about six eggs per female. The life-cycle was completed in ten days. Mating occurred soon after emergence, and the preoviposition period lasted about 2–3 days. Unmated females rarely laid eggs, and their life-span averaged six days as compared to 14 days for mated females. The female:male ratio was 2:1. The parasite rarely attacked previously paralysed hosts, and the preferred hosts were the older, larger larvae. A description of the egg and larvae is given.

Pre-treatment of females of Lucilia cuprina (Wied.) with the synergist piperonyl butoxide increased the resistance factors of an organophosphorus-resistant strain Q to four organophosphates in comparison to the susceptible strain LS. However, pre-treatment with S,S,S-tributylphosphorothrithioate (TBPT) reduced the resistance factors of Q to three organophosphorus insecticides. As TBPT is an esterase inhibitor, it is suggested that esterases contribute to resistance in the Q strain. Resistance to diazinon in the Q strain is due to a single, partially-dominant gene on chromosome 4. By the use of the backcross and discriminating dose technique, resistance to parathion, fenitrothion, chlorfenvinphos and fenitro-oxon (dimethyl 3-methyl-4-nitrophenyl phosphate) (the latter two were synergised by piperonyl butoxide to obtain a genetically discriminating dose) was also shown to be controlled by a single, partially-dominant gene on chromosome 4. It is concluded that this gene confers resistance to organophosphorus compounds in L. cuprina, probably by providing an esterase with enhanced ability to degrade organophosphates.

Studies were carried out in Nigeria on oviposition and the deadhearts caused by Diopsis macrophthalma Dalm. on ten rice varieties. The varieties were divided into three groups according to the numbers of eggs recorded on them. Strong positive correlations existed between (a) the numbers of eggs and tillers, (b) the numbers of eggs and deadhearts, and (c) the numbers of deadhearts and tillers. Some varieties compensated for damage by the production of new tillers. In the variety Suakoko 8, most of the eggs were confined to the leaf blades in young plants and to the leaf sheaths as the plants grew older. Peak oviposition occurred 30–40 days after transplanting. Some implications of the results for a pest management programme are discussed.

In the field in eastern Australia, adult females of Chortoicetes terminifera (Wlk.) underwent stages of body growth, fat accumulation and then egg maturation. Rainfall, and the resulting condition of the feed, determined the speed of development through the stages. If feed was dry, development was slow and stages could be suppressed; but even with feed that was only ‘dry-green’ locusts grew normally, accumulated fat, and then matured eggs after migration. If lush green pasture occurred following rain on the adults, they persisted and soon began to mature eggs. Thus females oviposit in the area where they hatched only if pastures there are lush green, thus ensuring some food for their offspring.

Observations were made over a two-year period on the growth and natural enemies of Lantana tiliaefolia and L. glutinosa growing naturally at nine sites covering different climatic areas of Paraná State, south Brazil. Lantana was found to be subjected to continuous attack by insects and/or fungi throughout the year, with different species causing damage at different times. Temperate-climate sites had a more diverse complex of insects and a greater intensity of attack than warmer-climate sites. Shrubs in sites which suffered severe insect attack, especially during the previous season, flowered and fruited significantly less than those which had suffered only light attack. Differential weighting of the principal phytophagous insects demonstrated that feeding by insects of some groups may be more damaging than that by others. The relevance of the results to the search for biological agents for control of lantana in Australia is discussed.

The growth of populations of Triatoma infestans (Klug) depends on temperature and blood-intake. Experiments are described which demonstrated the density-dependent relationship between population size, blood intake and population growth at different temperatures. The number of bugs feeding and their mean blood intake was lower at high bug densities than at low ones, both with restrained chickens and with unrestrained mice as hosts. When blood intake was restricted, the development times of all nymphal stages were increased, and female fecundity was decreased. Previous work showed also that reduced blood intake led to an increased tendency for adult flight. It is thought that at high bug density the three factors, increased development times, decreased fecundity and increased flight, operate to restore the population to a stable density without promoting an increase in mortality. The mechanism linking population density to nutritional status seemed to depend on host irritability, which interrupted the bugs' feeding. Bugs which passed a certain threshold meal size would not resume feeding if interrupted, even though their blood intake was well below normal. The difference between the minimal threshold meal and a normal meal is thought to provide the nutritional elasticity within which the development processes are regulated. It is suggested that this mechanism is characteristic of K-strategists, whereas r–strategists such as mosquitoes tend to continue attacking, even if interrupted, until they achieve a normal meal.

In a revised classification of the Tropiduchidae, which includes a number of species injurious to crops, the family is divided into 15 tribes, of which six (Cixiopsini, Eporini, Isporisini, Neommatissini, Remosini and Turneriolini) are proposed as new, two (Eutropistini and Tangiini) are given new status and seven are redefined. New subtribes (Clardeina, Neotangiina and Duriina) are erected in Eporini, Tangiini and Eutropistini, respectively, and Kazeruniina is given new status in the last. The genera Chiotasa and Habrotasa are transferred to Achilidae, Dolia, Hiracia, Karna, Parahiracia, Siebererella and Gastrinia to Issidae, and Kruegeria to Ricaniidae, and Dichoneura is brought into Tropiduchidae from Delphacidae. Biruga chariclo Fennah is transferred to Athestia to form a new combination, and Tambinia theivora sp. n. is described from material that included examples collected on tea.

Age-specific life-table data were collected over a year for field and insectary populations of Phoracantha semipunctata (F.) on logs of Eucalyptus grandis in Malawi. Most mortality occurred in the larval stage, and the major mortality factor was intraspecific competition. Severe overcrowding led to a reduction in population density from one generation to the next. Overcrowding also led to a reduction in beetle size and to a shift in the sex ratio in favour of males. Elimination of potential breeding sites is recommended as an effective control measure for this pest.

Investigations showed that there is a highly significant linear dependence of the percentage of bee (Apis mellifera L.) colonies detectably infested with Acarapis woodi (Rennie) on the number of colonies in England and Wales. A decline of infestation since 1947 corresponds to a decrease recorded in the number of colonies. The simplest explanation, based on current knowledge, is that the decrease has allowed the foraging activity of the remaining colonies to increase, so lessening the contact between old infested bees and young susceptible individuals sufficiently to hinder the spread and multiplication of mites within colonies.

The productivity of Glossina palpalis palpalis (R.-D.) reared in vitro via silicone rubber membranes on fresh guinea-pig blood equalled the productivity of flies fed in vivo on guinea-pigs. Over 50 days, the number of puparia per initial female was 3·0 in both cases. Puparial weights were greater than 31 mg throughout the four reproductive cycles. While fresh blood was an excellent diet for G. p. palpalis, freeze-dried guinea-pig blood was unsuitable; survival, reproduction and puparial weights were all low for flies fed on freeze-dried blood. The evidence lends support to the theory that there is no inherent nutritional deficiency caused by feeding on blood through a membrane.

The construction and functioning of a light-trap designed to catch only insects in flight at a height of greater than 5·5 m is described. The trap segregates the catch into hourly samples throughout the night.

Visual counting was found to be the most accurate method of estimating cereal aphid numbers in field studies in England. Vacuum sampling decreased in efficiency as aphid density increased, but could be a useful alternative to visual counts at very low aphid densities when the latter became too time-consuming. Cutting tillers for later washing in the laboratory was less efficient than visual counting as aphids, especially Metopolophium dirhodum (Wlk.), fell off the plants during sampling, but this method was useful in determining the proportion of different morphs of Sitobion avenae (F.) present at very high densities.

Alatae of Myzus persicae (Sulz.) were made to fly and then released directly onto untreated or chemically treated surfaces where settling behaviour was studied. Most aphids probed host-leaf surfaces even in the presence of vapour of (E)-β-farnesene, the main component of aphid alarm pheromone, or when related behaviour-controlling chemicals were painted on the leaf. Flown aphids attempted to probe most surfaces on which they landed, including glass and green paper. However, they did not probe white filter papers. Sublethal deposits of deltamethrin did not prevent initial probing on plant surfaces but caused uncoordinated leg movements which resulted in aphids falling from the plants.

The vertical distribution of flying mosquitoes was investigated in separate experiments in open savanna and over a fallow field system near Keneba Village in the tidal zone of the Gambia using suction traps located at seven levels (0·1, 0·25, 0·5, 1·0, 2·1, 3·9 and 7·9 m) on a scaffolding tower. Mosquito density declined progressively with height for Anopheles melas Theo., An. pharoensis Theo., An. squamosus Theo., An. ziemanni Grünb., Aedes dalzieli (Theo.), Ae. punctothoracis (Theo.), Culex tritaeniorhynchus Giles and Mansonia spp. Catches of C. thalassius Theo. and C. invidiosus Theo. increased with height to around 1 m and then decreased steadily although the 7·9–m trap consistently captured more C. thalassius than the trap below, presenting a bimodal vertical distribution profile. Flight altitudes of the two most abundant species, An. melas and C. thalassius, declined as the night progressed, but wind speed and lunar phase had no clear or consistent effects on flight levels. A functional relationship between flight altitudes and dispersal patterns of mosquitoes is suggested.

Dacus dorsalis Hend. infested eleven, D. cucurbitae Coq. five and D. umbrosus F. two of the eighteen common fruits and vegetables grown in Penang, West Malaysia. D. tau (Wlk.) infested bacang (Mangifera foetida), D. caudatus F. chilli (Capsicum annuum) and D. frauenfeldi Schin. water guava (Eugenia javanica), together with D. dorsalis. Pomelo (Citrus grandis) was found infested for the first time by D. cucurbitae. No flies were trapped using Capilure and trimedlure as baits. Cue-lure attracted D. caudatus, D. cucurbitae, D. frauenfeldi, D. occipitalis (Bez.) and D. tau. Methyl eugenol attracted D. dorsalis and D. umbrosus. Dorsalure was less attractive to D. caudatus and D. dorsalis than cue-lure and methyl eugenol, respectively, but it was equally attractive to D. frauenfeldi as cue-lure. Using traps baited with cue-lure or methyl eugenol in five ecosystems, the highest numbers of males of D. dorsalis, D. umbrosus, D. frauenfeldi and D. caudatus trapped were from a village, on a vegetable farm for D. cucurbitae, and D. occipitalis was only caught in a forest. Analysis showed that for each species of Dacus the difference between ecosystems was highly significant. The few examples caught in grassland were probably migrants.