The feeding rate of nymphs of Paulinia acuminata (Deg.) on Salvinia molesta was studied in the laboratory using single nymphs on different numbers of Salvinia leaves. Each successive instar ate more plant tissue, but at population densities likely to occur in nature it was unlikely that consumption rate could match the natural Salvinia growth rate. The controlling effect of Paulinia on Salvinia in Lake Kariba, Rhodesia, may therefore be negligible.

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.

During ultra-low-volume aerial applications of endosulfan at 14 g/ha for control of Glossina morsitans morsitans Westw. and G. pallidipes Aust. in savanna woodland in Zimbabwe-Rhodesia, the effects on other organisms were monitored. The numbers and varieties of arthropods, mainly insects, were studied by catches in light-straps and open trays. Mortalities amongst exposed aquatic insects, fish, frogs, mice and stingless bees (Trigona spp.) were noted. No deleterious effect of the insecticide was demonstrated, Other than on fish (Tilapia spp.) in shallow water.

Female Glossina palpalis palpalis (R.-D.) produced larger puparia when they fed on live goats that were injected intravenously with 200 IU of sodium heparinate/day than when they fed on untreated goats or on heparinised goat blood in vitro. Heparin did not produce the same effects when guineapigs were the hosts. Puparia from flies that fed on untreated guineapigs were larger than those from flies that fed on untreated goats. Heparin had no effect on the life-span or fecundity of females that fed on goats or on the life-span of flies that fed on guineapigs. However, the fecundity of flies that fed on guineapigs injected with 500 IU heparin/kg was greater than that of flies fed on untreated guineapigs.

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.

Loss rates of (Z)-8-dodecenyl acetate and related compounds from various dispensers were compared at 15, 20 and 29° C in the laboratory. Comparisons were also made of the performance of these dispensers in pheromone disruption trials against Cydia molesta (Busck) in peach orchards in Australia, in terms of the reduction of male captures at pheromone traps. Hollow-fibre and polymeric-laminate dispensers were superior to various polyethylene and silicone-rubber designs in providing a relatively constant release of pheromone in time, at rates readily modified by altering the dimensions of the dispensers.

Growth of the food fungus of the leaf-cutting ant Atta cephalotes (L.) on extracts of plants selected by the ants was shown to be affected by the plant species, the pH of the extract, the concentration of the sap or plant extract and pretreatment of the substrate by the ants. It was not possible to establish an unambiguous relationship between the rate of growth of the fungus on leaf extracts and the foraging preferences of the ants for the leaves. There were indications, however, that the fungus grows most rapidly on extracts of plant material preferred by A. cephalotes. Relative growth rates of the fungus on different substrates may be related to the presence of growth inhibitors rather than to nutrient availability.

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.

An analysis, using mathematical models, is presented of the ecological, genetic and economic factors that determine the optimal strategies for the long-term use of chemical control of Boophilus microplus (Can.) on cattle. As an illustration, the control of the tick in south-eastern Queensland is considered, but the approach is readily applicable in any other geographical area. It is suggested that optimal strategies take into account the need to delay the development of resistance to acaricides. The suggested strategies involve the use of tick-resistant Zebu-type cattle as a basis for tick control. High concentrations of acaricides are recommended to reduce seleotion of resistant ticks. Careful timing and moderation in the use of acaricides is also recommended to minimise the number of occasions on which resistant ticks are subjected to selection at times when they can successfully reproduce. As the spread of resistance is thought to occur primarily on moving cattle and before resistance is evident, stringent quarantine measures may slow down the spread.

Two years of field trials in Nigeria with the synthetic pyrethroids permethrin, cypermethrin and decamethrin against Glossina palpalis (R.-D.) and G. tachinoides Westw. are described. Laboratory tests were also made against G. morsitans submorsitans Newst. The three pyrethroids were applied successfully from the ground at 0·5%, 0·3% and 0·075%, respectively, to fly resting sites on vegetation using pressurised knapsack sprayers, populations of both species being eradicated after a single application of one insecticide. Following residual spraying from a helicopter, only decamethrin at 30 g/ha achieved complete eradication. It was thought that, with permethrin wettable powder at 200 g/ha, by modifying the spraying equipment and, with cypermethrin, by increasing the dosage to over 150 g/ha, both could be successful in the future. A new ‘sideways’ spraying technique tested using the helicopter gave promising results. Comparatively little harm was done to non-target organisms in the environment after spraying with any of the three pyrethroids, and it is expected that they may gradually replace the chlorinated hydrocarbons in future routine anti-tsetse operations.

Heliothis armigera (Hb.) has been shown to develop continuously in tropical areas but to become more dependent with increasing latitude on a pupal diapause to survive the winter. The changes that occur in pupal period under ambient conditions in Botswana were examined. Pupae formed in May were able to survive the winter period and produce adults in September. Laboratory work using artificial environments showed that this extended pupal period is not simply a response to low pupal temperatures but is induced by the low temperatures and short daylengths experienced by the larva. Pupae from larvae reared at 27° C and a 14-h daylength (non-diapause pupae) initiated adult development even at 13° C. Pupae from larvae reared at 18° C and a 9-h daylength (diapause pupae) had similar pupal periods to non-diapause pupae at 33 and 27° C. However, at 18 and 13° C, diapause pupae had much longer developmental periods than non-diapause pupae. More diapause pupae were produced at 18° C from larvae reared in a 12-h daylength than from those in 15- or 9-h daylengths. The variation and importance of this temperature-labile facultative diapause over the extensive geographical range of H. armigera is discussed.

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.

Field studies were conducted in Florida to investigate the behaviour of night-flying mosquitoes including Aedes sollicitans (Wlk.), Ae. taeniorhynchus (Wied.), Anopheles atropos D. & K., An. crucians Wied., Culex nigripalpus Theo., Culiseta melanura (Coq.), Deinocerites cancer Theo., Psorophora columbiae (D. & K.) and (Uranotaenia lowii Theo.) in relation to visually conspicuous objects. Adults of all species except Ae. sollicitans were taken in greater numbers in a large weathered plywood suction trap covered with black panels than in one without panels. However, both traps were attractive, as a transparent plastic suction trap covered with weathered plywood panels took larger numbers of all species except U. lowii than a transparent trap without panels. Buried suction traps furnished with visible risers (extensions) that made captures at 1·2 m elevations always captured proportionately larger numbers than buried traps with visible baffles that captured mosquitoes at ground level. A woodland species, C. nigripalpus, was captured in larger numbers toy traps furnisihed with visible risers and baffles than in traps furnished with transparent risers and baffles; however, collections of field species, e.g. Ae. taeniorhynchus, were smaller. The distribution of blood-fed and gravid females in collections from these traps provided some evidence that blood-seeking females are more responsive to visible objects than engorged or gravid females. These results are compatible with the hypotheses that (1) mosquitoes are attracted from a distance to visible objects, (2) in close proximity an avoidance action occurs and mosquitoes then pass over or around the visible object and (3) woodland species approach visible objects closely (<30 cm), whereas field species pass by at greater mean distances. Consequently, a larger percentage of visually attracted woodland mosquitoes than of visually attracted field species will be captured by suction traps. Depending upon trap design and specific behaviour, increasing the visibility of a suction trap can either increase or decrease trap collections

Detailed taxonomic studies of adult Cecidomyiidae reared from inflorescences and seed-heads of species of Gramineae and Cyperaceae during field surveys in Queensland and the Northern Territory of Australia in 1970–73 established that Contarinia sorghicola (Coq.) is restricted to non-indigenous crop and weed species of Sorghum section Sorghum that have been introduced to Australia by man and that three morphologically distinct species of Contarinia occur on native Australian grass species of Sorghum section Parasorghum. An earlier report that the wild grasses Dichanthium, Bothriochloa and Eriochloa serve as alternative hosts of C. sorghicola was not confirmed by detailed examination of long series of specimens reared from these hosts, nor was the pest species found on any other genera of Gramineae. It is therefore concluded that, in Australia, C. sorghicola has been spread (probably in contaminated seed) and maintained by grain and forage sorghums and that wild grasses are not potential sources of crop infestation. Eleven new species are described: C. roperi sp. n. and C. plumosi sp. n. from Sorghum plumosum; C. intrans sp. n. from S. intrans and S. stipoideum; C. sehimae sp. n. from Sehima nervosum; C. bothriochloae sp. n. from B. bladhii; C. dichanthii from D. annulatum var. fecundum and D. tenuiculum and possibly from D. affine and D. sericeum; C. passlowi sp. n. from D. annulatum var. fecundum; C. alloteropsidis sp. n. from Alloteropsis semialata; C. brevipalpis sp. n. from Eragrostis brownii; C. scirpi sp. n. from Scirpus lacustris and C. fimbristylis sp. n. from Fimbristylis bisumbellata. Characters of the female cerci were especially useful in diagnosing species, making it easier to identify females than males. Cecidomyiids of the genus Geromyia were reared from Setaria and cecidomyiids of the genus Lasioptera were reared from ten grass genera and one sedge genus during the surveys, but this material is not dealt with in detail. The needs for further field work and taxonomic studies are stressed and it is suggested that apertures on the dorsal surface of abdominal segment VIII in female C. sorghicola may be the openings of sex pheromone glands and would merit further detailed investigation.

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.