In a survey of adult ticks infesting livestock in Ethiopia, 33 species and subspecies were identified. The distribution and abundance of each are discussed in relation to ecology (altitude, climate and vegetation). Amblyomma variegatum (F.) is the most widespread and abundant tick parasitising cattle. A. cohaerens Dön. is common on cattle in wetter western habitats but is replaced by A. gemma Dön. in drier eastern areas. A. lepidum Dön. occupies intermediate habitats. The distribution of Boophilus decoloratus (Koch) is similar to that of A. variegatum. Hyalomma truncatum Koch and H. marginatum rufipes Koch are both common except in extremely arid and humid zones. H. anatolicum anatolicum Koch, H. anatolicum excavatum Koch, H. dromedarii Koch, H. erythraeum Tonelli-Rondelli, and H. impeltatum Schulze & Schlottke are usually associated with camels in semi-arid areas of eastern Ethiopia. Rhipicephalus evertsi evertsi Neum., R. sanguineus (Latr.) group and R. simus Koch do not display marked ecological preferences. East of the Rift Valley in semi-arid areas below 2000 m, R. pulchellus (Gerst.) is abundant on cattle and camels. R. longicoxatus Neum. and R. pravus Dön. inhabit drier localities, but R. lunulatus Neum. occurs only in wetter western areas. Species taken infrequently were A. nuttalli Dön., A. sparsum Neum., B. annulatus (Say), Haemaphysalis aciculifer Warb., H. leachii (Aud.), H. parmata Neum., H. spinulosa Neum., Hyalomma marginatum marginatum Koch, H. marginatum turanicum Pom., H. punt Hoogst., Kaiser & Pedersen, Ornithodoros savignyi (Aud.), R. longus Neum., R. muhsamae Morel & Vassiliades, and R. senegalensis Koch. The seasonal dynamics of the common species and observations on their relationships to tick-borne diseases of man and domestic animals are discussed.

The administration of dieldrin in the larval diet of Lucilia cuprina (Wied.) killed susceptible females with no pre-emergence mortality of males in a strain which contained a Y–autosome translocation linking dieldrin-resistance to the male sex. Laboratory assays of flight activity, sexual competitiveness and visual sensitivity revealed no significant differences between treated and untreated males. The life-span of treated males was slightly reduced at the highest dieldrin concentration used. In field releases, however, the recapture rate of treated males was much lower than for untreated males, indicating a major deficiency in the performance of dieldrin-treated males in the field that was not suspected from the laboratory tests.

Long distance migration by adults of Chortoicetes terminifera (Wlk.) in Australia was shown to be associated with the accumulation of fat-body lipid. Lipid was accumulated if the plant growth index was 0·3 or more within a week of the final moult; when the plant growth index was less than 0·3, there was little fat accumulation. Locusts with large amounts of fat-body lipid migrated on nights with warm strong winds, while those with little persisted.

LD50 doses of chloropicrin, ethylene oxide, ethylene dibromide, acrylonitrile plus 8% carbon dioxide, and acrylonitrile plus ethylene dibromide were found to decrease the productivity of adults of Sitophilus oryzae (L.) and Tribolium castaneum (Hbst.). Acrylonitrile, acrylonitrile plus methyl iodide and phosphine caused a reduction in productivity in S. oryzae but not in T. castaneum. Carbon dioxide decreased the productivity of T. castaneum. Carbon tetrachloride, methylene chloride, methyl bromide, methyl iodide, acrylonitrile plus carbon tetrachloride and acrylonitrile plus methylene chloride had little influence on the productivity. The productivity of T. castaneum exposed to trichloroethylene and acrylonitrile plus trichloroethylene was higher than in control batches. After exposure to acrylonitrile, reduced productivity was noted in adults of Callosobruchus chinensis (L.) that had been exposed as adults or pupae, and in T. castaneum but not S. oryzae that had been exposed as pupae.

Egg parasitoids attacking economically important pod-sucking Hemiptera on cowpea were collected in Nigeria and Tanzania. The three coreid hosts, Anoplocnemis curvipes (F.), Clavigralla tomentosicollis Stål and C. elongata Sign., and the two alydid hosts, Mirperus jaculus (Thnb.) and Riptortus dentipes (F.), form a pest complex that attacks grain legumes across Africa. Parasitoids attacking eggs of C. tomentosicollis were monitored on farmers' fields at a locality in northern Nigeria. Parasitism rose from low initial levels to maxima of 62% in 1978 and 51% in 1979. This mortality did not keep host populations below the economic injury level. The egg parasitoid complex of C. tomentosicollis was dominated by the scelionid Gryon gnidus (Nixon), while the encyrtids Ooencyrtus patriciae Subba Rao and O. kuvanae (How.) parasitised a large proportion of host eggs at times. Small numbers of Gryon fulviventris (J. C. Crawford) and the eupelmids Anas tatus spp. were reared. Observations on the biology and behaviour of O. patriciae are presented. This species occurred in both Tanzania and Nigeria and attacked all hosts studied. Rearings of all these parasitoids and also another species of Gryon, a species of Baeus and two species of Telenomus from eggs of the five species of Hemiptera are reported.

The development of a stock of Corcyra cephalonica (Stnt.) from Burma was followed carefully on a diet of wheatfeed, glycerol and yeast at constant temperatures ranging from 15 to 37°C and humidities from 15 to 90% RH. Two other stocks, from Nigeria and Malawi, were also studied under a few conditions. Limits for complete development from egg hatch to adult emergence were about 17 and 35°C at 70% RH. At 15°C, all larvae died early in development, but at 37·5°C a few managed to pupate. Highest survival and most rapid development occurred at 30–32·5°C and 70% RH. Development was completed in the range 15–80% RH, but few adults emerged at 15% RH and none at 90% RH unless a mould-inhibitor was present in the food. No second-generation larvae were obtained from adults reared and kept at 20°C and 70% RH. Egg period was influenced by temperature but not by humidity in the range 20–80%, RH. Eggs hatched at temperatures from 17·5 to 32·5°C. Hatch was adversely affected by low humidity, and very few hatched at 20% RH. Considerable variation in the rate of egg hatch between the three stocks may have been due to differences in the length of time each stock had been reared in the laboratory. Cold tolerance of eggs of the Nigerian stock was low. All eggs died at 10°C after a seven-day exposure, and at 15°C, although a few 0–1-day-old eggs exposed for 14 days hatched, none completed development to the adult stage. Although older eggs were slightly more cold-tolerant than younger ones at 10°C, they were less so at 15°C. Adult males tended to emerge earlier and live longer than unmated females. Adults of the recently collected Malawi stock were heavier and lived longer than those of the Burma stock that had been reared in the laboratory for many generations.

The preference of Culex quinquefasciatus Say for oviposition in rearing water (in which larvae and pupae of the same species had been reared), pond water, tap water (from a well) deionised water and food water (in which larval food was mixed) was tested in a 5 × 5 Latin square. Most oviposition occurred in rearing water, followed in decreasing order by pond water, tap water, deionised water and food water, the differences being significant except between pond water and tap water. Diel oviposition activity of females from wild-caught pupae was studied under tropical normal (light-day) photoperiod (LD 12:12), reversed (dark-day) photoperiod (DL 12:12) and continuous light (LL) for at least three consecutive days at average conditions of 29·3°C and 91% RH. Under conditions of alternate light and dark periods (normal as well as reversed), there was a circadian rhythm, which was unimodal, confined to the scotophase and concentrated in the first half of the scotophase. Under continuous light, activity was greatly depressed, with disturbances both in circadian rhythm and unimodality. It is concluded that the circadian rhythm of oviposition activity of C. quinquefasciatus is predominantly exogenous in nature and regulated mainly by photoperiod, activity being stimulated by darkness and inhibited by light.

A laboratory bioassay technique was used to compare the susceptibility to a granulosis virus of 16 field populations of Phthorimaea operculella (Zell.) in Australia. A difference of 11·6× was found between the most and least susceptible population, while a laboratory strain was over 30 × as resistant as some field populations. It is suggested that this variability might reflect the past history of exposure of different populations to the virus, which appears to be endemic. The implications for the use of this virus as a microbial control agent are discussed.

Flies of the genus Atherigona spend their immature stages in decaying organic matter (species of the subgenus Acritochaeta) or in the young shoots of various Gramineae (species of the subgenus Atherigona). Descriptions are given of two and 12 new species in these two subgenera, respectively. Most of these species are from India, and are of actual or potential economic importance.

To determine the extent to which the distribution of ovipositing Heliothis armiger (Hb.) might be ‘clumpy’ rather than random, the numbers of eggs on cotton throughout the 10 000 km2 Sudan Gezira were subjected to analyses of variance. It was found that at any time there was less variability within than between areas, highly significantly less for units of 600–700 km2. Within all areas, the numbers of eggs varied very significantly with time and many-fold increases in numbers of eggs occurred simultaneously over thousands of square kilometres. In every three-day period, there were two or more significantly different levels of infestation, each extending over areas ranging from a few hundred to several thousand square kilometres; the boundaries of such areas changed continuously, and no consistent differences or patterns were found. These findings suggest that redistribution of mobile populations of moths takes place over large distances. At all times there were areas with egg numbers below those considered economically serious; this has been utilised in new control strategy and tactics which have been effectively implemented experimentally. Larval spraying appeared also to reduce oviposition for at least three days and could in part account for some, but certainly not all, of the differences between areas.

The Rhyzobius (or Lindorus) ventralis frequently referred to in the literature of biological control is shown to be a mixture of two distinct, though similar, species. The origin of the confusion is traced to the nineteenth century searches in Australia for insects to control scale insect infestations on citrus and other crops in California. Adults of the two species are defined and illustrated, and a key is provided for their separation. Lectotypes are designated for R. ventralis (Erichs.), its synonym Scymnus restitutor Sharp and for S. halli Broun, newly synonymised with R. ventralis. A lectotype is designated for Platyomus forestieri Muls., the second species of the complex, here transferred to Rhyzobius, and for S. circularis Sharp, newly synonymised with R. forestieri. Distribution data for both species, based on actual specimens examined, are listed, and their Australian distribution is summarised in a map. Past usages of ‘ R. ventralis’ as a biological control agent are reviewed in the light of the revised taxonomy. The taxonomy and nomenclature of Rhyzobius Stephens is discussed in order to establish the correct generic placement of and binomina for R. ventralis and R. forestieri.

Effective control of Ephestia cautella (Wlk.) by Blattisocius tarsalis (Berl.) has occasionally been observed in warehouses. It has been postulated that this control is negated by fumigation under sheets, because of differential effects on the moth and its predator, and removal of alternative prey. The biology of B. tarsalis was studied at 27°C and 73% RH. On eggs of E. cautella, development took 5·9 days and there was 7% mortality; on eggs of Tribolium oastaneum (Hbst.), development took 7·4 days and there was 48% mortality. When offered a choice of eggs of the two pest species, the mites very rarely preyed on those of T. castaneum. The number of E. cautella eggs consumed (after correction for partial consumption) was 3·8 (total) by nymphs, 2·4/day by ovipositing females, 1·5/day by non-ovipositing females, and 0·8/day by males. The sex ratio (female: male) was 2·5:1. Adult life-span averaged about 55 days (maximum 153 days), and the oviposition period lasted about 20 days. Females laid up to 5 eggs/day at peak oviposition. The potential rate of increase of B. tarsalis on E. cautella eggs was very high, far exceeding that of its prey. These data confirm previous postulates concerning the role of B. tarsalis in natural control of E. cautella, and support the hypothesis that fumigation reduces predator-effectiveness. Modification of control regimes might allow greater natural control by the mite and reduce the increasing pest status of the moth.

Life-cycles and voltinism are described for Rhyzobius ventralis (Erichs.) and R. forestieri (Muls.) living in the region of Sydney, Australia, and also the role each plays in its particular biocoenosis. Colour variation and wax production are described for the larvae, prepupae, pupae and adults of both species, also the defensive and feeding behaviour. New and known host records are listed for both species. Reasons are suggested for the success, partial failure or failure of the species as biological control agents in various parts of the world.

Potato plots in southern England were covered by polyethylene sheeting perforated by 9-mm slits that opened to permit expansion as the plants grew. The slits admitted rain and also some aphids. Covered plants received 93% less immigrant aphids than exposed plants. The greatest protection was from Myzus persicae (Sulz.) (99%), whilst noncolonising species were reduced by 77%. It is improbable that the barrier to movement presented by the polyethylene would differentiate between incoming species or that M. persicae, for which potato is a preferred host, would escape more readily once inside the cover. This suggests that the behavioural barrier to alighting is in response to the reflection of high wavelength light at the polyethylene surface which affected M. persicae more than other species. The method has potential in protection of crops from aphids.

A ground survey to map the distribution of Glossina prior to the initiation of a control programme was undertaken in an area of more than 100 000 km2 in the Sudan and Guinea savanna zones of Mali. The area extends from 11°13′ to 14°15′N. and 5°53′ to 10°24′W. The Challier-Laveissière trap was the main survey tool, but other methods were used when the traps did not catch flies in areas suspected of being suitable for Glossina. The results are compared with existing distribution maps of the area, including one based solely on interpretations of earth satellite photography of the area. Infestation by G. morsitans submorsitans Newst. was continuous west of 8°20′W. and intermittent east of this. Apparent recent advances of G. m. submorsitans and G. palpalis gam-biensis Vanderplank were noted, but G. tachinoides Westw. seemed to have receded. Possible reasons for these differences between species are discussed.

Females of the Pakistan strain of Apanteles flavipes (Cam.) (which originates from Japan and is maintained on larvae of Chilo partellus (Swinh.) reared on maize) were readily attracted to maize stems but not to sugar-cane stems in the laboratory. Ovipositor probing occurred in the presence of unwashed host larvae, particularly of C. partellus and/or frass from host larvae fed on maize. Ovipositor probing did not occur in the presence of dried frass, dried frass that had been remoistened with water or frass from C. partellus fed on a diet of gram (Cicer arietinum) flour. The Pakistan strain of A. flavipes is morphologically identical to a strain of A. flavipes imported from India into Florida and established on Diatraea saccharalis (F.) fed on a soyabean flour-wheat germ diet. Reciprocal crosses between the two strains (Pakistan and USA) and between the F1, adults produced both male and female progeny. Nevertheless, behavioural differences between the strains were found in laboratory tests in that the USA strain responded more strongly to larvae of Acigona steniellus (Hmps.) fed on sugar-cane, was more attracted to sugar-cane stalks than to maize stalks and was not encapsulated by D. saccharalis larvae, whereas at least one-fifth of the Pakistan strain larvae were encapsulated. The existence of different strains of Apanteles flavipes adapted to different graminaceous crops suggests that parasite plant preference as well as host preference and suitability must be considered during attempts to introduce exotic parasites. It is recommended that A. flavipes strains adapted to sugar-cane be introduced into Pakistan for establishment on stem-borers of sugar“-cane.

Psila rosae (F.) overwinters in Britain in both the larval and pupal stages. Overwintering pupae formed in October and November at soil temperatures of between 10 and 16°C entered diapause. A period of similar temperature in the laboratory during the prepupal stage also caused pupae to enter diapause. Overwintering larvae continued to feed and gain weight; they pupated in early spring at soil temperatures of 2–8°C but did not enter diapause. The sensitivity to diapause-inducing conditions decreased between November and March, associated with changes in developmental temperatures and pupal weight. The differential effects of temperature on larval, pupal and diapause development together serve to synchronise adult emergence from the overwintering population. The mechanisms which allow overwintering by a variable proportion of larvae and pupae also provide the opportunity for the development of a third generation of adult flies in October and November.

Water-based ultra-low volume (WULV) applications to cotton at fourday intervals of a 1% a.i. polyurea-based microencapsulated formulation of the pheromone inhibitor 9-dodecenyl acetate (E/Z 80:20) in a 0·2-ha field cage in Malawi resulted in an average reduction of 60·2% in nightly mating of females of Diparopsis castanea Hmps. A relatively constant level of inhibitor was maintained by spraying with 30 g/ha initially and decreasing by 10% with each successive spray. Examination of the mated status of 1712 female moths sampled on 88 occasions revealed that, in the presence of inhibitor, mating increased linearly with increasing population density from 22 to 2844 moths/ha (equal numbers of males and females). In an openfield trial, WULV applications of 30 and 60 g of 1 % a.i. microencapsulated inhibitor/ha to isolated cotton plots (0·4–1·2 ha) at seven- and 14-day intervals had no measurable disruptive effect on released populations of moths as measured by oviposition and larval infestation of the crop, although there was some reduction in egg fertility and catches of males in pheromone traps in the treated plots. Timeseries analyses by gasliquid chromatography (GLC) of the residual inhibitor on filterpaper discs and cotton leaves in the field gave similar results, and GLC measurement of inhibitor on filter papers removed at intervals from the test plots showed that inhibitor loss was very rapid, typically 60% within two days and almost 100% after six days. Loss of inhibitor was less rapid in the field cage and under laboratory conditions. Physical and chemical evaluation of microcapsule deposition on cotton plants revealed that spray droplets penetrated to all parts of the plant but that deposition was greatest on the upper laminae of the top leaves of the plant. Methodology for assessing the success of mating-disruption experiments is described and discussed, and the failure of the open-field experiments is attributed mainly to the rapid loss of inhibitor from the formulation in the field.

Hourly and nightly catches of Heliothis armiger (Hb.) and H. punctiger Wllgr. at a site adjacent to 2000 ha of commercial cotton in the Namoi Valley of New South Wales, were analysed in relation to various environmental factors and showed that wind speed, temperature, night-length and (H. armiger only) moonlight exerted a significant influence on trap-catch. For H. punctiger and H. armiger respectively, these factors accounted for 80 and 60% of the deviance in hourly catches but only 70 and 40% of the variation in nightly catches. Wind speeds of more than 1·7 m/s suppressed the catch of both species but had a greater effect on H. punctiger than H. armiger. Whereas with both species, the optimum temperature for trapping was about 27°C, temperature had a greater influence on the catch of H. punctiger than of H. armiger. Bright moonlight was estimated to reduce the catch of H. armiger by 49%, but no significant effect was detected for H. punctiger. The analysis revealed a number of occasions for both species in which the hourly distribution of catch and/or the change in catch between successive nights was aberrant. With H. armiger, these inconsistencies appeared to be associated with changes in population due to adult emergence, whereas for H. punctiger the most likely cause seemed to be changes due to movement. The combined effects of wind speed, temperature, night-length and moonlight were used to adjust the nightly catches of each species according to the environmental conditions prevailing on a ‘ standard’ night. This was defined as a typical summer's night with temperatures decreasing from 28·8°C at dusk to 20·6°C at dawn and ideal catching conditions, i.e. no moon and wind speed never exceeding 1·7 m/s. As such, the adjusted catches could be taken as indices of moth abundance. These showed that H. armiger had three discrete periods of abundance, characterised by the presence of large numbers of young moths and spaced at intervals suggesting successive generations. A similar pattern was lacking in H. punctiger, which was abundant only during the first half of the season. Except during periods of emergence (H.armiger), or once when spraying occured during daylight, the aerial application of insecticides to the cotton adjecent to the light-trap resulted in marked reductions in the populations of both species.

Light-trap catches of Dysdercus bimaculatus Stål and weekly phenological records of its host-plants over a period of three years on Barro Colorado Island, Panama, are discussed in relation to a year-long study of population growth at selected plants. Population build-up of D. bimaculatus occurred on a sequence of seed crops from wild host-plants in the dry season. Each year, the largest number of bugs caught in the light-trap occurred after a drop in vapour pressure deficit marked the end of the dry season. Thus, the population appears ‘poised’ to attack cotton crops maturing in the late wet season. A stepwise linear regression indicated that each year, the variance in size of Pseudobombax septinatum crops (maturing at the end of the dry season) explained the largest proportion of variance in the light-trap capture of D. bimaculatus. However, estimates from the field study indicated that Ceiba pentandra crops were more important than P. septinatum in building up numbers of adult cotton stainers. The discrepancy between the field study and the longterm phonological monitoring survey would be resolved if D. bimaculatus adults experience a dispersal flight at the end of the dry season. This flight would enable the insect to locate better-quality seed crops in drier habitats that mature in the late wet season, such as Sterculia apetala or cotton. Light-trap captures at the end of the dry season in areas such as Barro Colorado Island where Ceiba and Pseudobombax occur, could be an index to the intensity of attack on cotton crops in nearby drier areas.