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.

Kagan J., Beny J.-P., Chan G., Dhawan S. N., Jaworski J. A., Kagan E. D., Kassner P. D., Murphy M. and Rogers J. A. (1983) The phototoxicity of some 1,3-butadiynes and related thiophenes against larvae of the mosquito Aedes aegypti and of the fruit fly Drosophila melanogaster. Insect Sci. Applic. 4, 377–381.

Due to a publishing error, butadiynes was incorrectly printed as butadienes throughout the above article.

We regret these errors and stress that they were not caused by the author, but were introduced after he had corrected the proof.

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.

The infection rates and transmission characteristics of sterile male Glossina morsitans centralis, G. austeni and G. tachinoides for Trypanosoma vivax, T. congolense and T. brucei were studied. Teneral males were irradiated with 10 krad in a 137caesium source under ambient conditions. Five groups of teneral males of each species were sterilised by irradiation with 10 krad caesium source under ambient conditions and then fed for 3 days, together with five groups of normal males of their respective species, on three goats infected with T. vivax, T. congolense or T. brucei. The mean sterility rates were 98, 93 and 90% for G. m. cenlralis, G. austeni and G. tachinoides respectively. The mean percentage mature infection rates in the irradiated as against the controls of G. m. centralis, G. austeni and G. tachinoides were respectively 27.3 ± 9.5/27.7 ± 11.1, 4.0 ± 1.4/4.0 ± 2.6 and 14.8 ± 7.0/12.2 ± 5.0 for T. vivax; 24.6 ± 5.2/30.3 ± 4.3, 0.7/0.3 and 0.3/0.3 for T. congolense; and, 22.7 ± 2.6/23.4 ± 3.1, 1.1/0.2 and 0.7/1.7 for T. brucei. The transmission rates and frequency to A/J mice were very high and did not differ between the sterile and normal males. There was also no difference in the pattern of the diseases in the goats challenged by sterile or sexually fertile males of the three tsetse species. These results indicate that releases of sterile male tsetse in tsetse control programmes will potentially increase the trypanosomiasis risk in the affected area. Hence appropriate measures should be integrated in any SIR method of tsetse control campaign in order to provide adequate protection to man and his associated livestock.

Trypanosome infection rates in tsetse, Glossina pallidipes Austenin five areas along the Kenya coast were studied for 2 years (1980–1982). The total percentage infection rates were 12.62, 7.24, 9.50, 7.86 and 7.97 for Ukunda, Diani, Muhaka, Shimba Hills and Mwalewa, respectively. The respective values for males were 3.13, 4.16, 5.17, 5.03 and 8.13. Overall there were more trypanosome infections due to; Trypanosome congolense followed by T. vivax and T. brucei, although these varied among the localities. The age of the flies, their feeding patterns and regular use of chemoprophylaxis in local cattle were the main factors affecting infection rates.

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 paper presents a way of estimating average daily mortality rates of female tsetse from ovarian age distributions. This technique was applied to monthly biconical trap samples of G. palpalis taken during and after insecticidal campaigns in the Bouaflé region of Ivory Coast. A clear inverse relationship is demonstrated between the annual mean number of females per trap per sample at 10 separate sites, and the mean annual mortality rates calculated for them. Local variation in the impact of insecticides is explained in terms of the grouping of the sites either side of a level of natural mortality above which tsetse populations cannot be sustained through reproduction alone.

A theoretical model for density dependent population growth is presented and applied to a particular control situation, that of the sterile insect release method. The model demonstrates that the effectiveness of any particular level of induced sterility (or mortality) is crucially determined by the natural resilience of the target population.

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.

In 1981 an attempt was made to eradicate a 300 km2 fly-belt of Glossina pallidipes (Austen) in the Lambwe Valley of western Kenya by means, principally, of sequential aerial application of endosulfan aerosol spray. The progress of spraying operations was monitored entomologically by surveying for fly with biconical traps sited in main habitats of thicket, Acacia woodland and coniferous plantation, and by age-grading females caught between spray cycles.

Although nine spray applications of relatively heavy dosages of insecticide were carried out, the campaign ultimately failed to accomplish its objective. Females which had clearly survived and bred in the intervals between spray cycles were found throughout the area. By the end of operations, the tsetse population appeared to have been reduced by 99.9% in thicket and woodland, and by 99% in coniferous plantation. Nevertheless, on the basis of a crude estimate of total fly numbers in the Lambwe Valley, several thousand flies possibly remained after spraying.

Monthly post-spray monitoring showed that the population in thicket fully recovered in about 12 months, but to only 20–30% of its original level in woodland and plantation two years after spraying. The population in thicket maintained an approximate equilibrium density after recovery, indicating that density-dependent processes had re-established a regulatory effect. There was some evidence that this was brought about in part by fly movement. Calculations of the population growth rate gave a value for r, the instantaneous rate of increase, of 0.015 per day; equivalent to a finite rate of increase of 1.610 per month, and a population doubling time of 45 days. Some possible ecological reasons for failure to achieve eradication are discussed.

The effects of gamma irradiation from a 60Co-source on Glossina palpalis palpalis (Robineau-Desvoidy) were established in laboratory tests. Dose-response data indicated that fecundity was reduced by about 95% following exposure of late stage puparia or young adults to 11–13 krad in air and 15–18 krad in a nitrogen atmosphere. None of the treatments had a detectable influence on the viability, mating behaviour, inseminating capability or competitiveness of the adult males.

When irradiated males were combined in varying ratios with untreated males and females, increasing numbers of sterile males resulted in a considerable reduction in pregnancy stages beyond the egg stage, an increasing proportion of parous females with an empty uterus due to expulsion of a dead embryo after embryonic arrest or due to ovary blockage and an increasing percentage of females with a degenerating egg in utero.

Remating of inseminated females with fertile males during the period when most of them had emptied their uterus (day 14–20) after embryonic arrest, had no noticeable effect on the sterility rate.

A most important consequence of recurring embryonic death was a detectable imbalance between intra-uterine and ovarian development. Some aberrations can be used as additional criteria for monitoring the effectiveness of sterile males released in the field.

Females irradiated in the pupal or adult stage displayed a normal receptivity and insemination rate and survived distinctly longer than untreated controls. Moreover, they built up abnormally abundant fat bodies and showed multiple mating scars (restricted to the palpalis group species) and completely atrophied ovaries.

It is postulated that the release-recapture and examination of the reproductive tract of irradiated females during an advanced stage of sterile release vector control operations would give evidence of mating that could expose the existence of relic wild populations, particularly when the natural tsetse population has been reduced to, levels below the threshold detectable by conventional techniques.

The combination of a trapping system of insecticide impregnated screens and biconical traps followed by the release of sterile males led to the complete control of Glossina palpalis gambiensis and Glossina tachinoides in the agro-pastoral zone of Sideradougou. This area, situated south of Bobo Dioulasso, Upper Volta, in the Guinea savannah, covers an area of approx. 3000 km2. Along more than 650 km of rivers, bordered by gallery forests and infested by riverine tsetse, 6500 impregnated screens were placed during 4 months of the dry season, followed by the release of sterile males in the rainy season. For release purposes, colonies of 150,000 producing females of G.p. gambiensis and 85,000 females of G. tachinoides were maintained in industrial colonies on artificial membranes. Reinvasion of the project area was prevented by two barriers consisting of biconical traps impregnated with synthetic pyrethroid in one and simple biconical capture traps in the other. The screens reduced the initial fly population by 94% and permitted the release of only 35 sterile males per km of river to attain the planned ratio of seven sterile males to one wild male. Regular surveys showed that, after 4 months of release of sterile males, the relic fly population was constantly decreasing and tending towards disappearance.

An economic evaluation based on the production costs of the sterile males together with the costs of field operations showed that this combination of two non-pollutant methods was competitive with other methods of tsetse control.