Attempts were made to find alternative, less persistent, toxicants to aldrin for use in baits against Anoplolepis longipes (Jerd.) in the Seychelles. More than twenty toxicants were tested (some in more than one formulation) for effectiveness as poisons and for repellency to ants at the concentrations used in baits. None was as effective as aldrin, but certain formulations of pirimiphos-ethyl, pirimiphos-methyl and mecarbam were promising because they gave good kill of ants in the laboratory and were of relatively low repellency and therefore acceptable in bait formulations.

In Cameroun, about a dozen species of insects were associated with oil palm inflorescences. All except Prosoestus spp. visited female inflorescences after visiting male inflorescences during anthesis and transported pollen to the receptive female flowers. At a rough estimate, about 20 000 individuals visited each female inflorescence during the period of receptivity, and about 70% of the pollen transported was viable. In Peninsular Malaysia, Thrips hawaiiensis (Morg.) is almost certainly the main pollinating agent. Some 200 000 individuals were estimated to visit a single male inflorescence. They also visited female inflorescences, Where up to 7.3 thrips per flower were estimated to be present at any one time, each carrying 4–5 pollen grains, of which 76% were viable. In Peninsular Malaysia and Sabah, a momphid moth. Pyroderces sp., may contribute to oil palm pollination. As natural pollination of all oil palms in Cameroun and taller palms in Peninsular Malaysia is considered adequate while in most areas of Sabah where few insects visit the flowers it is inadequate, it is concluded that the insects observed achieve pollination so the oil palm should be considered an entomophilous rather than an anemophilous plant.

The response of F1 larvae from reciprocal crosses of susceptible × organophosphorus-resistant strains of Lucilia cuprina (Wied.) to diazinon was intermediate in relation to that for larvae from the parental lines to the chemical. Exposure to a concentration of 0·4 p.p.m. diazinon for 24 h was lethal to susceptible larvae. Close agreement with 1:1 ratios of susceptible: hybrid resistant larvae was obtained when larvae from a repeat backcross series were exposed to 0.4 p.p.m diazinon in each generation. Additionally, there was correspondence between response lines for larvae of backcrosses 1 and 3. This information, plus the recovery of a homozygous-resistant sub-strain by exposure of F2 larvae to a level of the chemical that discriminated against susceptible and hybrid genotypes, suggest that diazinon resistance in the larvae is due to a major allele.

During an epizootic of bluetongue virus disease of sheep in Cyprus in the autumn of 1977, 16 species of Culicoides were collected in light-traps and 4 species were collected from breeding sites. Two of the species found breeding in close association with sheep and goats are potential vectors of bluetongue virus. The possibility of a third species being a vector in Cyprus is discussed.

Difficulties were experienced in determining the susceptibility status of populations of Rhipicephalus evertsi evertsi Neum. to organochlorine acaricides. A susceptible strain of this species was found at Maswa, Shinyanga District, Tanzania. Susceptibility for toxaphene, dieldrin and γ–BHC was assessed by means of an FAO recommended test method, the oil-based packet test. A homogeneously responding resistant strain was built up from larvae from Ngong, near Nairobi, Kenya, that had survived a discriminating dieldrin concentration of 0·2%. These showed resistance factors of 10·8 for toxaphene, 30 for γ-BHC and 95 for dieldrin. The F1 cross between susceptible and resistant populations responded homo-geneously and was intermediate in resistance between the parental strains, with resistance factors of 8·7, 9 and 8·1 for ithese compounds, respectively. Larvae from backcrosses of F1 adults with the parental strains showed stepped ld-p lines such as would be expected in a case of inheritance of a single gene allele with partial dominance for resistance. A population of R. e. evertsi near Dar es Salaam, Tanzania, was controlled by application of 0·3% toxaphene despite it having resistance factors similar to those of the F1 hybrids.

Catches of Glossina palpalis palpalis (R.-D.) and G. tachinoides Westw. at high and low densities with hand-nets, biconical traps and an electric back-pack trap in Nigeria indicate that both types of trap are inferior to hand catching for routine checks of G. palpalis and G. tachinoides populations. Hand catching is recommended as being most suitable for large-scale surveys, assessment of control following insecticide spraying and classical fly-rounds. The biconical trap is recommended for use in experiments of a limited size, monitoring of fly populations on livestock ranches and around Villages, and for capturing flies for dissection. The electric trap is recommended for use in sampling flies in areas of medium and high density and possibly for blood-meal identification. Some blood-meals of G. palpalis were identified.

As in previous limited entomological studies carried out toward the end of the 1969 yellow fever epidemic on the Jos Plateau, Nigeria, the vector mosquito was not identified, additional observations were made in April, June, August-September and October 1970. In the three study areas selected, each the scene of yellow fever cases in 1969, special attention was given to the larval habitats and adult biting cycles of five species of Aedes (Stegomyia). Holes in the broken or cut stems of Euphorbia kamerunica, a plant commonly used as hedge in rural settlements, proved to be well utilised by larvae of Ae. aegypti (L.), Ae. africanus (Theo.) and Ae. luteocephalus (Newst.), the latter species being the most abundant. Collections of adults on human bait, mainly from 12.00 to 21.00 h, showed that species of this subgenus comprised between 70 and 89% of all mosquitoes captured in June-October. Ae. luteocephalus always predominated, followed by Ae. aegypti, then Ae. vittatus (Big.), Ae. africanus and Ae. simpsoni (Theo.). Ae. aegypti was found not to be a domestic, household-inhabiting species in the study areas. The indications are that Ae. simpsoni is not strongly anthropophilic on the plateau. Two arboviruses, UgMP 359 and a member of the Bunyamwera group, were isolated, from Ae. (Aedimorphus) dentatus (Theo.) and Anopheles funestus Giles, respec tively; no isolations were made from 2033 adults of Stegomyia.

Many tomaspidine froghoppers are pests of crops in South America, and their current taxonomic position frequently does not reflect their true affinities. In this second revisionary contribution, certain generic features of Tiodus, Iphirhina, Tunaima and Urubaxia are described and compared, and 2 species are transferred to Maxantonia, 3 to Tunaima, 1 to Kanaima, 1 to Prosapia and 5 to Mahanarva. Huaina gen. n., Choconta gen. n. and Tiodus rufescens sp. n. are described. Monecphora fortunata Lall. is suppressed under Kanaima vittata (Wlk.), and Maxantonia scita (Wlk.) is recalled from synonymy with Monecphora quadrifasciata (Lep. & Serv.).

Spodoptera exempta (Wlk.) is predominantly a migrant species, but in southern Africa it is known that it can breed through several successive generations in one area. Similar observations were made for the first time in East Africa. Studies on populations in the Lambwe Valley in western Kenya revealed that during two years when the populations were monitored and one year when information was available from local farmers there were three generations each year during the period corresponding with the long rainy season. It is suggested that the Lambwe Valley presents a suitable habitat for the species to sustain its population and probably forms a breeding area for moths that might undergo large-scale migration.

Catches of Glossina morsitans morsitans Westw. and G. pallidipes Aust. attracted to an odour-baited trap in riverine woodland in Rhodesia declined by about three-quarters over a 50-day period in the hot dry season. Concurrent catches from refuges suggested that the decline in trap catches was due to a reduction in population densities rather than a decreasing responsiveness of tsetse to the trap. Of G. pallidipes marked and released 250, 1250 and 2250 m from the trap, the percentages recaptured in the trap after 5 days were about 20, 10 and 4, respectively, and after 40 days about 28, 15 and 13. The sustained responsiveness to the trap and efficiency with which marked flies were removed suggested that odour-baited traps at an economical spacing of roughly one per 10 km2 could produce effective control of G. pallidipes.

A laboratory method was developed to evaluate the effectiveness of volatile sulphur-bearing chemicals as attraotants for newly hatched larvae of Delia antiqua (Mg.). The 27 chemicals evaluated included mono-, di-and trisulphides, mercaptans, thiosulphinates, thiosulphonates, thiopropanal S-oxide and ‘onion oil’ (a complex mixture of volatiles). Larvae were placed in the centre of a petri dish and chemicals were presented either in glass tubes or on white absorbent discs 6 mm in diameter. One tube or disc contained 10 000, 1000, 100, 10, 1 or 0·1 nl of the test chemical and the other a similar amount of diethyl ether. The solvent did not attract the larvae and was used to dispense 0·1–100 nl amounts of the test chemicals. Most of the chemicals tested were unattractive at 0·1 nl and repellent at 10 000 nl. At the intermediate amounts, all attracted at least 40% of the larvae and 13 attracted more than 80%. Onion oil at 1 nl and methyl trisulphide at 10 nl elicited the greatest response, attracting 95% of the larvae. A possible method is suggested for using these chemicals in the field to attract newly hatched larvae away from onion seedlings.

A method for maintaining adults of Hydrotaea irritans (Fall.) in captivity in groups, pairs or singly, is described. Male flies lived about half as long as females. Plies required carbohydrate and water for survival. A 50% honey solution, a 50% sucrose solution, thistle flowers and aphid honeydew all met the energy requirements of H. irritans, unlike blood, serum, milk, sweat, dung and mucus. The number of eggs matured was greatest on a diet of carbohydrate with blood or serum. Fewer eggs developed in flies given a diet of carbohydrate with milk, and very few on a diet of carbohydrate with horse sweat, cow sweat, dung or mucus. No eggs were matured by females fed on carbohydrate alone. All males had active spermatozoa whether or not they were fed on blood, but females were only inseminated after both they and the males with which they were kept had been given blood. The insemination rate was low at 13·3%. Females required more than one blood-meal, but not more than one every third week, in order to develop the maximum number of eggs.

The flight activity of Chrysopa carnea Steph. was studied during 1970–77 using 21 suction traps sited between 50 and 58°N. in northwestern Europe. Flight continues until late October and early November, well beyond the time (late August) when reproductive diapause is initiated at these latitudes. Flight ends as an all-or-none response to changing daylengths, the most northern populations having a shorter critical photoperiod, about 10 h 20 min, between morning and evening civil twilights, than the most southern ones, the critical photoperiod of which is about 10 h 45 min. By contrast, the critical photoperiod for induction of reproductive diapause is longer in northern populations. At latitudes less than 30° N. there is no winter dormancy but there is sometimes aestivation during the hottest period of the summer. In C. carnea, uniquely, winter dormancy has two distinct components, reproductive diapause and loss of flight activity, each controlled independently by photoperiod.

The effects of age on calling behaviour of virgin females of Chilo suppressalis (Wlk.) were investigated. The results show clearly that patterns of calling varied with age. The frequency of calling was high in females up to 4 or 5 days after emergence and thereafter decreased rapidly. The number of calling bouts increased slightly in older moths. Bout length became longer with increasing age. The total duration of calling, therefore, increased gradually with age. On average, calling began 3 h 49 min after light-off on day 1, but thereafter, the time of start became earlier each day by 10 to 40 min per day. It seems that the change of calling patterns with age is correlated with increased reproductive maturity of females.

Four features concerned with the baiting of leaf-cutting ants were studied. A liquid concentrate containing attractive and arrestant substances together with a toxicant was developed for the production on site of cheap baits for leaf-cutting ants in Brazil by addition to suitable locally available particulate carrier materials (matrices). The five non-organochlorine insecticides that performed best in previous baiting trials were further tested in Brazil at slightly higher concentrations against Atta cephalotes (L.), which had been shown to be the most difficult species to eradicate; two of these showed promise as substitutes for the well-proven but persistent organochlorine insecticide mirex. Other tests showed that bait widely scattered over a nesting site containing colonies of A. sexdens (L.), in simulation of a broadcast application from aircraft or ground dispensers, was as effective as that placed by hand at entrance holes of nest mounds. Weathering tests in a forest area showed that spoilage by rain and fungal growth, not loss of insecticide, were the main factors governing the effective life of dried citrus pulp baits under wet or humid conditions.

The identity of Empoasca dolichi Paoli, a serious pest of beans and other crops in Africa, was confused. While processing a collection of leafhoppers from Malawi, E. dolichi was found mixed with other species. The identity of E. dolichi was established with reference to its type material, and two new species and a new subspecies of Empoasca from Malawi and two new species from Nigeria are described. New characters that might help specific identification and show the relationships of groups of species are also illustrated and described.

Hybrids of Nephotettix virescens (Dist.) and N. nigropictus (Stål) have been bred in the laboratory, and they could transmit rice tungro virus even though only one of the parents is a vector. In the present paper, evidence is presented based on coloration and on male genitalia that suggests that such hybrids occur in nature. The potential danger from such hybrid vectors is pointed out, and taxonomists are alerted to the risk of accepting such hybrids as new species, thus completely hiding their potential as vectors.

The Polovodova ageing technique was applied to females of Anopheles darlingi Root in the northern part of Mate Grosso, Brazil, in April 1978; 1·5% of the females had oviposited at least four times and were old enough to be potential vectors of malaria. The oldest female dissected had oviposited six times. The mosquito has a resting period of at least 24 h between oviposition and the next blood-meal. There was a pronounced peak of biting activity, consisting largely of nulliparous females, at dawn and dusk.