Sandflies caught from termitaria at Tseikuru (Kitui District) and Masinga (Machakos District) were dissected and examined for the presence of Leishmania. Leishmanial parasites were found in the guts of 12 out of 112 Sergentomyia garnhami from Tseikuru and in 2 out of 48 S. antennatus from Masinga. Five of the 12 S. garnhami and 1 of the 2 S. antennatus had leishmanial parasites in the malpighian tubules. Electron microscopic investigations revealed that in the malpighian tubules of S. garnhami the parasites were either free in the lumen or in close contact with the basement membrane.

When marked adults of the tick Rhipicephalus appendiculatus were released into 25 × 25 cm plots in the field, their vertical distribution in the habitat was assessed after recovery, by comparing the number of ticks on the vegetation with those on the soil surface. In the hot dry season, 73% of the ticks were recovered. Of these a third were on the vegetation and two thirds at the soil surface. Out of the 67% recovered in the wet season, only 15% were found at the soil surface and the rest on the vegetation. In the cool dry season, 75% were recovered with roughly equal proportions on the vegetation and the soil surface. This suggests that only a third of the ticks would be available to be picked up by the hosts during the hot dry season. Two thirds would be available during the wet season and only half were available during the cool dry season.

Batches of engorged Rhipicephalus appendiculatus ticks (females, nymphs and larvae) were placed in gauze-covered vials in the field at monthly intervals and left to complete development. The ticks were placed in open areas and tree shaded areas; the latter being consistently cooler.

The duration of development varied seasonally and was inversely related to environmental temperature. The mean time to oviposition ranged from 5 days during the hot dry season to 25 days during the cool dry season. There was a high larval mortality during the larval to nymphal moult. However, the available data shows that the mean time to larval–nymphal moult ranged from less than 2 weeks during the hot dry season to 7 weeks in the cool season. The mean time to nymphal–adult moult ranged from less than 3 weeks in the hot season to over 13 weeks in the cool dry season. Egg hatching ranged between 3 weeks in the hot dry season and 15 weeks in the cool dry season.

On exposure of maize grains mixed with groundnut oil at a dose of 20 ml/kg, 100% mortality of the rice weevil, Sitophilus oryzae (L.) was observed within 24 hr and 100% at 10 and 5 ml/kg in 2 and 3 days.

Egg-laying and progeny development in the rice weevils were completely prevented at groundnut oil doses other than 1 ml/kg at which the number of eggs laid and progeny developed were 27 and 38% of those in the oil-free control during the same period. When maize treated with oil at 10–20 ml/kg was reinfested after 19 weeks with fresh adult rice weevils, less than 42% of them had died. The total number of progeny that emerged on week 23 from the two higher doses of oil was 38% of that emerging from the control.

Groudnut oil does not affect the viability of maize grains and damage after 25 weeks. Viability of maize grains was only 6–13% after oil treatment at 10–20 ml/kg compared to 100% in the untreated control.

A study on the biology of the sorghum midge, Contarinia sorghicola Coq., and the damage and crop loss it causes was carried out under field conditions during the main planting season at Mbita, in Western Kenya. The developmental period from egg to adult ranged from 17 to 34 days with a mean of 23 days. On average, 3.2 adult midges emerged from each damaged spikelet. Adult emergence was bimodal, with a major morning peak and minor late afternoon peak. A predator, Diaperasticus erythrocephala Olivier (Dermaptera: Forficulidae), was found preying on newly emerged adults. The level of damage varied among 38 sorghum lines tested, with the size of the panicle (r = 0.73; P < 0.05) and the number of days to 50% flowering (r = 0.49; P < 0.001) influencing the level. The level of damage for the sorghum variety Serena ranged from 1.8 to 97.7% and grain yield from 22.3 to 0.9 kg/50 m2, respectively for plantings during the months of March–June. The relationship between damage and crop loss was almost perfect (r = 0.998; P < 0.001).

Major workers are the dominant caste in foraging parties of Macrotermes michaelseni; they also have the largest sternal gland, with the highest potential trail-laying activity. The termite utilizes pheromonal trails along open-air foraging routes, surface galleries and in the subterranean gallery network. Thus, surface galleries appear to serve primarily as protective structures to foraging traffic, while trails lead foragers to food sites. Well-established trails on paper lost activity within 2–3 hr under open-air field conditions. In a choice situation, a trail leading to food source was 30–40 times stronger than that directed to an empty food chamber, suggesting that food influences trail-laying and recruitment behaviour of the termite.

A high level of resistance to chlorpyrifos has been detected in Culex quinquefasciatus larvae from Dar es Salaam. To study the impact of this resistance on the routine anti-larval spraying programme with this chemical, pit latrines, cess pits and soakage pits were examined regularly after spraying. Larvae were eliminated immediately after spraying, but in most cases they re-appeared about 2 weeks later. Bio-assays with susceptible and resistant larvae in water samples from the pits showed that in most cases there would have been sufficient insecticide residue for at least 10 weeks to kill a susceptible population, but resistant larvae could survive in the water from about 2 weeks after spraying. Chemical analysis showed that the water was toxic to resistant larvae so long as it contained about 0.02 mg/l chlorpyrifos. These observations might have suggested that the routine spraying programme every 10 weeks would be having very little impact on the population now that resistance has evolved. However, in fact, adult densities in houses in a year with spraying on schedule were much less than in years when many sprayings were missed owing to shortage of supplies. Thus the regular spraying programme still apppears to have a beneficial effect.

A one-year survey was carried out in two brackish water pools to study the incidence of Amblyospora sp. in field populations of Culex sitiens larvae at the Kenya coast. Salinity of the pools, water temperature, and rainfall patterns were also recorded to check their possible effects on the infection rates. Levels of infection in both pools were low, and ranged between 2 and 15%. Infections occurred in a wide range of salinity. Statistical analysis (t-test) showed no significant correlation between infection rates and neither salinity, temperature nor rainfall in the field.

Marked individuals of Zonocerus variegatus were released in batches of 100 per developmental cohort at definitive loci in either an open field of mainly giant star grass, Cynodon sp. or a cultivated farm of cassava, Manihot esculenta. The distance and direction of movement of individuals in any given stadium were determined in metres and angular degrees. The mean distances moved by marked Z. variegatus for each day of observation were determined by Clark's root mean square formula.

The results showed that older cohorts covered more distance during a given period than young cohorts. However, while the first instar nymphs moved significantly less than any other cohort, the differences in the mean daily distances moved by nymphs of the second through the sixth developmental instars in the cassava farm were not statistically significant. For all cohorts, Z. variegatus covered significantly more distances in the open field than in the cultivated farm, suggesting that the availability of food inhibited the rate of dispersal of Z. variegatus. There was no significant difference in the number of Z. variegatus found on the different aspects of the compass.

Aleurolobus barodensis (Maskell) was more abundant than Neomaskellia andropogonis Corbett on sugar-cane in Pakistan. Azotus delhiensis Lal, Eretmocerus sp., Prospaltella flava Shafee, Amitus sp. and Tetrastichus sp. parasitized nymphs and pupae of A. barodensis and E. serius Silvestri those of N. andropogonis. Chrysopa carnea Steph., Brumoides suturalis (F.), Catana parcesetosa (Sic.), Oenopia sauzeti Muls., Scymnus sp. and S. nubilus Muls. preyed on the immatures of the aleurodids.

In Peshawar valley where the crop is aerially sprayed twice a year to control Chilo infuscatellus Sn., Tryporyza nivella F., A. barodensis and Pyrilla spp., the rate of parasitism on A. barodensis was very low and its density was very high, being 330 immatures/leaf at Charsadda and 425 at Mardan in November 1979. At Sialkot (Punjab) where the crop is not sprayed, the rate of parasitism, mainly by A. delhiensis and Amitus sp., at this time was 22% and the density of A. barodensis was 70.4 immatures/leaf. The maximum rate of parasitism was 71% in January. The abundance of A. barodensis in Peshawar valley seems to be due to the mortality of natural enemies because of aerial spraying, therefore, judicious use of insecticides and redistribution of natural enemies in these areas is recommended.

Cowpea is one of the most widely grown leguminous crops in Africa: in Kenya it occupies over 66,000 ha and Coast Province ranks second to Eastern Province with about 5200 ha. It is an important food item consumed both as a vegetable and as a grain. Unfortunately, it suffers from both preharvest and postharvest infestations which accounts for serious losses of the crop. With the introduction to Kenya of improved varieties from IITA, Nigeria, such losses would be increased due to varying susceptibility in different pest ecosystems. The objective of this study therefore was to observe the infestation of the IITA varieties and compare them with local cowpea varieties collected from different parts of Kenya. The work was conducted at C.A.R.S., Mtwapa from 1979 to 1981 inclusive. From the study, five different bruchid species were identified as infesting cowpea varieties in the field. These were Collosobruchus rhodensienus; C. phaseoli; C. chinensis; Bruchidius atrolineatus; and C. analis; in order of decreasing abundance. Over 50% of the bruchids found in the field were C. rhodensienus while Zabrotes spp. and C. maculatus (F) were never encountered in the field. Although the IITA materials were introduced because of their yield potential, it was found that some of them were as susceptible to preharvest bruchid attack as the locally available materials. The short rains season had more bruchid infestations than the long rain season. There were also fewer eggs on pods of local varieties and fewer bruchids emerging from seeds of local as compared to IITA varieties. The results however were not significantly different. Further work should be done to establish the complex of bruchids found in stored cowpea varieties, the losses caused and control measures applicable to reduce damage.

Ovipositional nonpreference and larval development of stalk-borer, Chilo partellus Swin., on leaf-whorl and stem of 70 sorghums comprising of released varieties and hybrids, experimental high-yielding varieties, lines selected for stalk-borer resistance and local cultivars were studied in the laboratory. Data on oviposition of egg-masses as well as on number of eggs, larval duration, larval mortality and pupal weight on leaf-whorl and stem of individual variety were separately recorded. These characters were also correlated with number of holes, number of tunnels and per cent tunnelling observed in the field.

The egg-masses per seedling ranged from 0.32 to 2.25, while eggs per seedling varied from 2.25 to 20.80 on different varieties. These were highly correlated (0.92**) characters. The varieties SPV nos 35, 101, 110, 232, 257, 289, 291, 309 and 311, E 302, E 701, CSV nos 3, 6 and 8R and Aispuri were relatively less preferred for oviposition. Larval development took 17–32 days on leaf-whorl and 33–62 days on stem of the various varieties. The larval duration on leaf-whorl as well as on stem were more than average on SPV nos 35, 103, 107, 110 and 310, E 302, E 701, CSV-8R, IS 2312 and Aispuri. The larval mortality ranged from 1.7 to 95.0% on leaf-whorl and 13 to 95% on stem. Significantly higher larval mortality on leaf-whorl of SPV nos 35, 101, 292 and 311, E 302, CSV nos 3, 6 and 8R was recorded. It was 11.5 and 29.6% higher on SPV-35 and CSV-8R respectively than the most resistant variety, IS 2312. Larval mortality on leaf-whorl of early maturing varieties was 8.1% more than late varieties. The mean pupal weight was 65.55 ± 3.82 mg on leaf-whorl and 51.65 ± 4.93 mg on stem. The pupal weights were 47–75 mg on leaf-whorl and 33.5–47.7 mg on stem of local varieties.

Larval duration was positively correlated with larval mortality on both leaf-whorl and stem and negatively with pupal weight on leaf-whorl. Larval duration and mortality on leaf-whorl were negatively correlated with per cent ‘dead hearts’, and number of tunnels per plant. Larval duration and mortality on stem were also negatively and significantly correlated with holes per peduncle and per cent tunnelling. The magnitude of correlations of larval duration and mortality with tunnelling parameters were higher than that of oviposition. Though ovipositional nonpreference and antibiosis act together to determine the degree of resistance, antibiosis has a greater effect on Chilo resistance than the effect of ovipositional nonpreference.

The antibiosis factor(s) affecting larval development exists in leaf or in stem or in both the plant parts. Short peduncle varieties were less preferred for oviposition.

Glossina morsitans morsitans were maintained on rabbits immunized with crude tsetse midgut proteases. Newly emerged flies fed on these rabbits showed a depressed trypsin/proteinase VI activity, 6.5% of these flies failed to empty their crops as readily as controls, and 7.8% cases stayed as long as 11 days with undigested bloodmeal. Of these flies 4% exhibited premature larviposition.

Laboratory reared populations of Spodoptera exempta (Wlk.) had higher net reproductive rate and capacity for increase on maize, Zea mais L. and star grass, Cynodon dactylon (L.) Pers. than on Kikuyu grass, Pennisetum clandestinum Chiov., Guinea grass, Panicum maximum Jacq. and Setaria plicatilis (Hochst.) Hack. These parameters were greatly influenced by the larval mortality, but in all cases they were greater than one demonstrating that S. exempta populations can multiply on all the host plants tested. Since no populations with stable age distributions are known for S. exempta the net reproductive rate is more appropriate than the capacity for increase in estimating its population growth.

The activity pattern of the ant, Cataulacus guineensis F. Smith, was found to be diurnal; trailing starts around 6.00 a.m. and ends around 6.00 p.m. The effect of meteorological factors on the activity pattern of the ant was also investigated and rainfall was found to be the most important factor influencing the ant's activity. The ant was found to be generally very active throughout the year, except when the harmattan conditions were very severe.

The species was found to be mainly a canopy forager, although occasionally it might forage on the ground. The mean foraging space was 555.0 m2; but when nests (colonies) were close together, overlapping of foraging spaces did occur.

The courtship behaviour of male Spodoptera exempta (Wlk.) has been quantified and used as a method of bioassay for the female sex pheromone. Virgin females become attractive to sexually mature males from 72 hr after emergence and henceforth their attractiveness increases gradually until they have mated. Mated females start losing their attractiveness to males gradually after mating and 72–96 hr after mating they cannot produce any courtship response in males. Amongst virgin females, crude pheromone-gland extract and synthetic pheromone compounds, it is the older live females and the crude extract at 0.1 female equivalent that produce highest responses in males. A certain degree of cross-attraction between three coexisting species has been noted, both by using live insects as well as synthetic pheromone compounds of these species under laboratory bioassays. Possible interspecific pheromone-related implications are discussed.