Adults of Zonocerus variegatus (L.) from the dry-season population in southern Nigeria were shown to exist in two forms, one with relatively long wings and the other with relatively short wings. The wet-season population normally existed as the short-winged form, but the insects had the capacity to develop long wings. Long-winged insects had welldeveloped flight muscles and were capable of flight. Flight in the field occurred before sexual maturation and may have led to downwind displacement of individuals over considerable distances.

Many West African mosquitoes fly at low levels when crossing open country. Experiments were therefore conducted in the Gambia on the effect of high fences on their dispersal. In the first experiment, a circular mosquito-proof fence 2·9 m high and with a radius of 18 m was constructed. Catches inside on human bait of Mansonia spp. were about 60% lower than catches outside the fence, whereas catches of Anopheles spp. in the two sites were not significantly different. In unbaited suction traps, catches of Mansoniainside the fence were significantly lower in traps 0 and 0· m above the ground, but not at 1 to 3 m, than in traps at similar levels outside. This suggested that, after flying over the fence, mosquitoes had not resumed normal ffight levels by the time they were trapped in the centre of the circle. In a second experiment, a much larger fence was erected, 6 m high and with a radius of 65 m. Catches were conducted in experimental huts in the centre of the enclosed area and at a distance of 70 m outside it when the fence was erected and again after its removal. Catches of Mansonia spp. on human bait in the hut inside were 46% of the total catch in the two huts when the fence was erected and 48% after its removal; catches of Anopheles spp. (A. gambiae Giles and A. funestus Giles) were 43% with, and 53% without, the fence. In calf-baited light-traps, catches of Mansonia were 41 % of the total with, and 38% without, the fence, and those of Anopheles 58 and 44%. Thus the presence of the 6·m fence had no significant effect on the density of mosquitoes in the centre of the enclosed area, and it is concluded that mosquitoes were flying freely over it. Due to the prevailing low winds in the area, passive transport of mosquitoes over the fence by the wind was not thought to be important.

The encyrtid genus Tachinaephagus is revised, and a key to species presented. Four species are described and illustrated: T. stomoxicida sp. n., a very important parasite of Stomoxys nigra Macq. from Uganda and Mauritius; T. malayensis sp. n. from Malaysia; T. javensis sp. n. from Indonesia; and T. congoensis sp. n. from Zaïre. A lectotype is designated for T. zealandicus Ashm., the type-species of Tachinaephagus, and this genus as defined here is restricted to larval and pupal parasites of Diptera. Zeteticontus, which is superficially similar, is in fact distinct, and characters separating the two genera are tabulated.

Individuals and groups of adults of Zonocerus variegates (L.) were fed on various food-plants. Somatic growth, maturation and reproduction were all faster in group-fed insects than in isolated ones. Dry-season insects grew faster and produced greater numbers of egg pods than did wet-season ones. Short-winged insects developed faster than long-winged ones. Zonocerus that fed on cassava (Manihot esculenra) had a shorter somatic growth period and produced greater numbers of egg pods than insects that fed on any other foods. Cassava-fed Zonocerus had a greater efficiency of conversion of digested food to body substance, particularly during oocyte growth, than similar insects given other foods. Food plants such as Citrus and A spilia were inefficiently utilised, and often compensatory increases in consumption occurred. The success of the large dryseason population of Zonocerus in southern Nigeria is probably due to the increase in cassava cultivation.

The tick infestation patterns observed during 1966–73 are described for wild animals and cattle on the northern plateau of north-eastern Zambia, the eastern plateau and the intervening Luangwa valley. The seasonal periodicity of adult Amblyomma sparsum Neum., as observed on buffalo, was similar to that of A. variegatum (F.). Five major depart ures from the patterns of infestation previously found in the Central Province were observed. Boophilus decoloratus (Koch) was partially or totally replaced on cattle by B. microplus (Can.).Rhipicephalus appendiculatus Neum. although present on wild fauna in the valley, was absent from cattle on the eastern plateau. R. evertsi Neum. was absent from much but not all of the northern plateau and occurred in very low numbers only on the cattle of the eastern plateau, yet was present on the wild fauna of the Luangwa valley. Hyalomma marginaturn rufipes Koch was practically absent from cattle on the northern and the eastern plateaux and from the wild fauna, except buffalo, of the valley; H. truncatum Koch was abundant on cattle on the northern plateau and on the wild fauna of the valley, but on the eastern plateau cattle it occurred in low numbers only. A. pomposum Dön, was found on cattle in one area of the northern plateau, the only specimen of Amblyomrna on that particular herd. These anomalous findings are discussed in relation to the situation elsewhere in Zambia and in neighbouring territories.

A method for releasing genetically altered strains of Lucilia cuprina (Wied.) as free-falling larvae from aircraft was tested. Full-fed genetically marked third-instar larvae were released from aircraft flying at a height of 150 m and speeds of 120 or 220 km/h. Progeny tests of adult flies trapped subsequently indicated that released male larvae survived to the adult stage and were competitive with wild males for females.

Flies attracted to odours from 500 to 11 500 kg of livestock were captured using electrified netting in the Zambesi Valley, Rhodesia. Catches of maleGlossina morsitansWestw., Tabanidae, Stomoxyinae and non-biting muscids reached maximum levels at odour concentrations produced by only 500–3500 kg of livestock, but catches of femaleG. morsitans and both sexes of G. pallidipes Aust. increased over the whole range of concentrations tested. With the maximum dose of odour, up to 7100 tsetse were caught in 3 h. The proportion of tenerals in catches of Glossina was not affected by odour concentration. Daily catches of Giossina were positively correlated with daily maximum temperatures. The maintenance of large catches of flies for 60 days and the indication that larger catches are possible suggest the feasibility of employing odour-baited traps for tsetse control.

Rhodnius prolixus Stȧl was successfully reared for three generations on a diet of defibrinated pig blood fed through Parafilm or silicone-rubber membranes. Reproduction in terms of the number and sizes of eggs produced was superior to, while survival from egg to adult was equal to that reported for, insects fed on live hosts. The technique appears equally applicable to the rearing of Panstrongylus megistus (Burm.), Triatoma infestans (Klug) and T. brasiliensis Neiva. The inadequacy of cow blood as a diet for R. prolixus was manifested in a decrease in adult size after two generations and in a reduction of egg weight from 30 to around 16 mg per female per week. This was accompanied by a corresponding reduction in egg hatch from 90 to about 50%.

The genotypes of chromosomally-identified individuals from natural populations of the known species of the group of Anopheles gambiae Giles were scored for the enzyme protein structural loci coding for adenylate kinase (Adk), α-naphthyl acetate esterase (Est-1, Est-2, Est-3), glutamic-oxaloacetic transaminase (Got), α-glycerophosphate dehydrogenase (αGpd), hexokinase (Hk), isocitric dehydrogenase (Idh), lactic dehydrogenase (Ldh), ‘leucine’ aminopeptidase (Lap-2), malic enzyme (Me), octanol dehydrogenase (Odh), phosphoglucomutase (Pgm-1, Pgm-2), 6-phosphogluconic dehydrogenase (6-Pgd), phosphohexose isomerase (Phi) and superoxide dismutase (Sod), following starch gel electrophoresis. In the material examined, Est-1, Est-2, Est-3, Got, ldh, Lap-2, Odh, Pgm-1, Pgm-2 and Sod were segregating for two or more alleles; unique alleles at the Est-1, Got and Sod loci produced species-specific phenotypes in A. melas (Theo.), species C and species D, respectively. The further sampling of A. merus Dön, populations supported the presence of a unique SOD phenotype by which this species can also be identified. Of the other enzyme systems examined, no activity following electrophoresis was detected for aldolase and fructose-1,6-diphosphatase, and the resolution of acid and alkaline phosphatase, glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, malic dehydrogenase and xanthine dehydrogenase was too poor under the particular electrophoretic conditions for genetic analyses of the enzyme phenotypes.

A previously published method for determining the physiological age of female Lucilia cuprina (Wied.), based on a linear relationship between their rates of ovarian development and temperature, was tested under field-cage conditions. It was found that ovarian development was more rapid than that predicted by thermal summation based on ambient temperature. A re-examination of the rate of development-ambient temperature relationship, over a wider temperature range that that used previously, showed that the development threshold temperature was 8·2°C rather than 11·3°C. Thermal summation using the revised threshold also fell short of the observed day-degree totals. An effective temperature for ovarian development (ambient temperature plus a temperature excess proportional to the incoming solar radiation intensity) was fitted to the data from the field cage. This relationship gave accurate predictions of ovarian development (±8%) for flies that were released into the field.

Adults of Hydrotaea irritans (Fall.) in south-western Scotland were caught in a Manitoba trap and a black suction trap baited with carbon dioxide. Trapped flies were dissected to investigate their reproductive condition, their blood feeding activity and whether they were newly emerged. Trapping of the first gravid females in August was accompanied by a sharp decline in adult activity. The proportions of females in the various ovarian categories suggested that there is a preliminary phase before host-seeking begins, attraction to animals during most of the cycle and a behavioural change at the end. Females with eggs at stages I, II and III accounted for 94% of all females caught; the only females with blood in the gut were in these categories. Some males also were obviously blood-fed. There was a single mating period lasting five weeks. Inseminated females were first trapped in the third week of July, when the numbers of males started to decline, and within five weeks all females trapped were found to have been inseminated. After this, no more males were caught. Only females with eggs in stages later than stage II of the first ovarian cycle were inseminated. H. irritans was univoltine, with two but not three complete ovarian cycles during the summer. There was no difference in feeding or reproductive development between flies from the two traps.

When incorporated into an artificial diet or painted on the surface of the membrane containing the diet, solutions of the insect repellent GD 880 (2-methyl-2-(octylamino)-1-propanol) killed aphids, whilst extracts of neem seeds (Azadirachta indica) or extracts of the bodies ofMyzus persicae (Sulz.) deterred settling and larviposition of apterous adults. The deterrent effect occurred even when the painted membrane was covered by a similar but untreated membrane. When applied in culture solutions to the roots of young kale plants, GD 880 and extracts of neem influenced aphids on the foliage only at concentrations that visibly affected plant growth, but neem extract (and to a lesser extent GD 880) decreased aphid colonisation when painted on kale leaves at non-damaging concentrations.

Dissection of 2337 female Glossina morsitans morsitans Westw., collected over an 11-month period (118–420 per month) from a game reserve in Zambia, revealed that abortion is a regular feature of tsetse reproductive biology and apparently the most frequent reproductive abnormality in the tsetse population. It occurred among ifies in all ovarian cycles from 1 to 7+4n (minimum age 10–80 days) and apparently involved all pregnancy stages. Neither follicular degeneration nor egg retention was encountered, suggesting that these particular reproductive abnormalities are infrequent in nature.

In laboratory colonies of Atta cephalotes (L.) and Acromyrmex octospinosus (Reich), discs cut from young leaves of several plant species were picked up more readily than those from old leaves. Pith sections impregnated with whole extracts of young leaves were consistently picked up in preference to others with extracts of old leaves, and non-lipid extracts were consistently preferred to extracts containing lipids. Arrestive properties were confined to the non-lipid extracts, and inhibitory properties were mainly found in the lipids, but removal of lipids from the whole extracts did not necessarily make them more arrestive. In most cases, dewaxing of leaves with chloroform made them more acceptable, and heating and freezing of leaves had a similar effect. Leaf waxes showed inhibitory properties. Wax extract of young leaves was often preferred to that of old leaves, and differences in preferences were observed for wax extracts from different plant species. The implications of these findings for the relationship between leaf-cutting ants and the vegetation that they cut are discussed.

Felled logs of twelve species of Eucalyptus were exposed simultaneously to attack by Phoracantha semipunctata (F.) in Malawi. Colonisation was assessed by counting the number of larval feeding channels on the surface of the sapwood. The level of colonisation varied significantly between different tree species. E. fastigata and E. paniculata were much more heavily colonised than any of the other species. Possible factors contributing to this variation in susceptibility are discussed. The more susceptible species should be the most efficient for control operations involving the use of trap trees.

Sticky traps baited with (Funemone cis-8-dodecenyl acetate or (Codlemone trans-8,trans-10 dodecadien-1-ol) were operated in plum orchards in Cambridgeshire, England, from 1974 to 1976. In addition to large numbers of the target species Cydia funebrana (Treitschke), males of 24 other tortricids were captured. These included species of Cnephasia, Celypha, Epiblema, Pammene and Cydia. As an aid to the correct identification and interpretation of trap catches, details are given of the more important species attracted by the pheromone baits.

On Mahé in the Seychelles, Anoplolepis longipes (Jerd.) is a pest, mainly because of the nuisance it causes to man and domestic animals but also because it increases the numbers of sap-feeding insects and the occurrence of sooty mould on plants. The most important sap insect associated with sooty mould on citrus and cinnamon was Ceroplastes rubens Mask., the numbers of which sometimes increased a hundredfold in the presence of A. longipes, and up to 90% of leaves were infected with sooty mould. The rapid population expansion of the ant on Mahé prior to 1973 has since slowed down, and infestations in some areas have diminished, possibly because of a decreasing source of protein. Movement of ant-infested material has initiated secondary infestations, which are difficult to eradicate once established. The ant is not considered a threat to conservation as differences between the fauna in infested and uninfested areas tend to be quantitative rather than qualitative. Attempts to eradicate the ant on Mahé would be costly and inappropriate. The use of toxic baits and sprays is recommended only where ants become a domestic nuisance, threaten productivity or reach Other islands in the Seychelles group.

Samples of 25 African populations of Aedes aegypti (L.) were examined for variations in scale-colour pattern of palps, halteres, abdominal tergites and metatarsi and in larval body colour. A colour index based on these characters showed domestic populations to be paler than populations found in forests. Classification of phenotypic and genotypic variations in the amount of pale scaling on palps, halteres and, especially, tergites revealed statistically significant differences between some of the populations. Although it was impossible to identify individual mosquitoes, population samples could be identified according to subspecific designations as A. a. formosus (Wlk.) and A. a. aegypti.

Following a demonstration of the role of ants in the dissemination of Phytophthora pod rot and an intensive study of the ant mosaic on cocoa at the Cocoa Research Institute of Nigeria, there was a need for a wide-scale assessment of the relative importance of different species of ant on cocoa farms in the major growing area of western Nigeria. Between 19 January and 6 February 1976, 50 trees were examined on each of 76 cocoa farms and all ant species visible from the ground were recorded. Sixteen species, or species-groups, of ants occurred on more than 1% of the trees, and their geographical distribution, habitat requirements and inter-specific relations were examined. The last of these were elucidated using principal components analysis, and the results are compared with earlier work on the ant mosiac. Any one cocoa farm only rarely provided a suitable habitat for more than one or two of the dominant species, and a diagram summarising the habitats is given. The potential usefulness of ant population manipulation is thought to be restricted in Nigeria by the undesirable effects of co-dominant and associated species found with the dominant species, Oecophylla longinoda (Latr.) and Tetramorium aculeatum (Mayr), which are regarded as beneficial in Ghana. The most important of the undesirable co-dominants is Pheidole megacephala (F.).

The leaf-cutting ants Atta cephalotes (L.) and Acromyrmex octospinosus (Reich) were tested in a moving-air olfactometer for their responses to a variety of odours from leaves, fruit, flowers, essential oils, other ants and a fungus garden. The line of a foraging trail established in still air tended to loop downwind in the presence of a laminar air flow. The ants exhibited positive, negative and neutral responses to the test odours, confirming the existence of attractants and repellents in substrate materials. Neutral responses to the odours of several of the materials that were acceptable for cutting showed that arrestive materials were not necessarily attractive. Ants orientating towards the source of an odour often secreted a pheromone trail. Atta and Acromyrmex responded differently to several of the materials tested, and the responses to odours of young and old leaves were not totally consistent with the observed cutting preferences. Removal of wax from non-attractive leaves made them attractive. Both species responded negatively to lemon-oil odour, but some Acromyrmex workers showed a hostile response. A hostile response was also elicited by the odour from other ants. Fungus-garden odour elicited a positive investigatory response, and no response was shown to queen odour. Laden Atta workers did not respond to an odour that was attractive to unladen ants, and laden examples of Acromyrmex responded in small numbers to such odours. The addition of attractive chemicals to baits for the control of leaf-cutting ants would improve pick-up by making the bait particle easier to find.