Agricultural treatments mainly against cotton and rice pests put a considerable insecticide pressure on larvae and sometimes adults of several vector species. Resistances to compounds which had never been used for public health, but were currently employed in agriculture were observed among vectors. It was also noticed that resistance level in some vector species was linked to the quantity of the compound used in the same area against crop pests.

Resistance in Anopheles gambiae in Africa, in An. albimanus in Central America, in An. culicifacies and An. aconitus in South East Asia, in An. sacharovi in Turkey, in Culex tritaeniorhynchus in the Far East as well as the DDT resistance in Simulium damnosum in West Africa, seem to be associated with the agricultural practices.

On the other hand, resistance did not develop in species which, due to their ecology, were not in contact with agricultural insecticide even in areas where DDT was applied for more than 20 years in house spraying. This is the case of An. dirus and An. minimus in Thailand and An. darlingi South America.

However several important factors like Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, have developed resistance for which agricultural treatments cannot be held responsible. It would be worth saying that the rise in malaria in certain countries, such as India, is only due to the increase of insecticide in agriculture after the “green revolution”.

The ovipositional responses of the stem-borer, Chilo partellus (Swinhoe), to the maize cultivar Inbred A are greater than the maize cultivar, Nyamula. These responses are elicited by certain characters of the plants that are perceivable prior to the moth's arrival on the plants (distance-perceivable) as well as those perceivable after arrival on the plants (contact-perceivable). Distance-perceivable characters were not found to be responsible for the difference in the oviposition on the two cultivars tested.

The contact-perceivable characters of the maize cultivars differ in eliciting oviposition by moths. Contact with the cultivar Nyamula elicits much less oviposition than with the other cultivar tested.

Relative susceptibility of laboratory-established cultures of four populations of Dysdercus fasciatus Sign. and one population each of D. nigrofasciatus Stal., D. cardinalis Gerst, and D. superstitiosus (F.) to topical applications of cypermethrin, fenvalerate and permethrin was investigated at Kibos, Kenya. The LD50 values of the three chemicals to populations of D. fasciatus were 0.0656–0.0757, 0.335–0.469, 0.442–0.505 μg/insect, respectively, while those for D. nigrofasciatus were 0.1690–0.2541, 0.481–0.504, 0.721–0.851 μg/insect. The LD50 values for D. cardinalis and D. superstitiosus were 0.1507, 0.714, 0.798 μg/insect and 0.0991 and 0.824 μg/insect of each of the three chemicals respectively. Based on D. fasciatus from Kibos as the reference strain, the relative susceptibility values of all populations of Dysdercus species studied were small ( < four-fold) indicating that resistance was not apparent in the cotton stainers. Of the three insecticides tested, cypermethrin was the most effective judging from the high toxicity ratios between it, fenvalerate and permethrin.

This paper reports the results of extensive pest surveys conducted on farmers' fields and pest population studies at two national research stations between 1979 and 1981 in Burkina Faso. Major findings indicate that, under normal planting conditions, infestation of the sorghum shootfly, Atherigona seccata is very low in farmers' fields. This pest appears to be restricted to research stations. Stem borer infestation is caused by a complex of species, and species predominance varies with rainfall. South of latitude 12°N, Busseola fusca is the predominant species but further north it is replaced by Acigona ignefusalis, which is a primary pest of pearl millet. Panicle damage caused by the sorghum midge, Contarinia sorghicola, varies with season; is usually very low in the dry northern Sahelian zone but severe south of latitude 13°N. Maximum midge populations occurred between mid-September and early October.

The effects of climate on the diurnal biting pattern of Simulium damnosum s.s. were measured at Jos Plateau, Nigeria. Rain in the hours prior to the catch inhibited morning activity by lowering the temperature and light intensity, and raising the humidity. Under shade there were no remarkable fluctuations in the light intensity, and no obvious peaks in activity; in sunny places, activity was bimodal, with a small morning peak and a pronounced afternoon one. The fastest changing climatic factor relative to an increase in the biting activity of flies was light intensity; followed by temperature.

Vertical distribution of different larval instars and pupae of Culicoides oxystoma in different depths in the mud and sandflats of Hooghly estuary were studied in relation to soil temperature and moisture at three stations in and around Sagar Island during March 1983 to February 1984. Temperature recorded higher in 0–3 cm depth and gradually decreased in subsequent depths. During the last part of the pre-monsoon (May and June) season, moisture was recorded minimum in 0–3 cm depth and gradually increased in greater depths, but in other seasons (monsoon and post-monsoon) the results were just opposite. Larval and pupal population showed a peak during post-monsoon then gradually declined in pre-monsoon and early monsoon. They were mostly encountered throughout the year from 0–3 cm depth except during summer months (May, June and July). First and second instar larvae were only recorded from 0–3 cm depth. Third and fourth instar larvae were distributed in all the depths, maximum in 0–3 cm. Pupae were never encountered from deeper depth (6–9 cm). Temperature and moisture act as important factors to control the vertical distribution of larvae and pupae of this species.

Polyphenism is a common feature in the mustard aphid, Lipaphis erysimi (Kalt.) in tropical countries. The function related changes in basic biochemical pool are reported during development of polyphenic forms. A gradual decrease in the protein content in this aphid was recorded, as the nymphs advanced in their instar number and reached adult stage. However, the protein content was significantly lower in the apterous forms as compared to alate. The number, density and mobility of protein bands varied as the nymphs passed through different instars and the number of bands was more in alate forms. The glycogen and trehalose contents showed a decrease upto the third instar and showed an increase in the fourth instar, but again declined in the adults of both the phases.

The termite Macrotermes herus builds domed earth mounds with no external openings. The internal structure is described here. There is no specialized ventilation system in the mound, unlike those of other Macrotermes species.

Screening of leishmanial parasites from domestic and wild animals was carried out in Kacheliba, West Pokot District. Spleens and livers of the animals were cultured in NNN diphasic medium. Thin smears of the same tissues were also made and stained with Giemsa stain and examined under microscope. Positive slide smears were obtained from goats and positive cultures obtained in four goats, one rat and two lizards.

The actions of diisopropylfluorophosphate (DFP), an irreversible anticholinestrase (Anti-ChE) agent, were studied on the glutamatergic neuromuscular synapse of insects. The present study reveals that DFP interacts with pre- and post-synaptic regions, also it gives alternative explanations of the symptoms of organophosphate poisoning in insects. Exposure of the metathoracic flexor tibialis muscle of Locusta migratoria to DFP (0.5 mM), at physiological solution, contained normal external calcium concentration (2 mM), increased spontaneous neurotransmitter release which was large enough to trigger action potentials (APs) and endplate potentials (EPPs). A cyclic pattern of APs and EPPs burses and silence periods were recorded. The spontaneous firing of APs and EPPs was calcium-dependent. Reduction of external calcium concentration abolished this phenomenon, suggesting a pre-synaptic site of action of DFP. A transient pre-synaptic depolarization, caused by the agent, could explain the spontaneous transmitter release and repetitive EPPs firing. The spontaneous activity, induced by DFP, was blocked by a sodium channel blocker such as tetrodotoxin. Exposure to α-bungarotoxin, α-Naja-toxin or atropine did not affect the spontaneous release of the transmitter induced by OP agent. Coupled with the pre-synaptic effect, a decrease in the peak amplitude of endplate current (EPC) and shortening of the decay time constant (τEPC) recorded after exposure to the flexor muscle to 1 mM DFP. Both the pre- and post-synaptic effects of DFP were reversible upon washing the preparation. The present findings shift the focus of the occasioners of hyperexcitation of insects treated with OPs from indirect effects of these compounds on the central nervous system (CNS) to direct effects on neuromuscular junctions and indirect effects on CNS.

The collapse of Glossina tachinoides populations, within a 27-month period of weekly sampling by means of unbaited biconical traps, in two peridomestic agroecosystems is described. Consistent removal of parous flies through trapping and low recruitment of young flies into the population, were largely responsible for unabated decline in the apparent density of both G. tachinoides populations. Reduction in the size of the resident pig population to below five pigs/week/agroecosystem triggered the collapse of both tsetse populations. Some ecological implications of these findings and their possible application in tsetse control are discussed.

Different ages of the two spotted spider mite Tetranychus urticae Koch and the predacious mite Amblyseius gossipi El-Badry eggs were exposed to selected concentrations of cypermethrin (500 ppm), flucythrinate (200 ppm), cyfluthrin (100 ppm), fenvalerate (200 ppm), Pyridaphenthion (25 ppm), dicofol (250 ppm), avermectin (10 ppm), and dimilin (50 ppm). Generally, the synthetic pyrethroids were effective on eggs especially those of A. gossipi. Dicofol was rather toxic to T. urticae eggs, while avermectin was only effective on older eggs of both species. Eggs treated with different pesticides at late stages took longer to hatch, particularly in the case of A. gossipi.

Larva of fifth instar silkworm, Bombyx mori L. (Lepidoptera: Bombycidae), parasitized by uji-fly, Exorista sorbillans (Weidemann) (Diptera: Tachinidae), consumed less food and egested less faecal matter than unparasitized one in the instar period. Uji-fly infested worm showed increased digestibility in the last 2 days while the unparasitized larva ingested excessive amounts of food than needed during these days. A reduction of 18.1% in the mean weight of parasitized worm at pupation was recorded. Further, parasitization resulted in 50.7% reduction in the mean cocoon weight and 51.12% reduction in the mean shell weight. Parasitized worms started spinning a day earlier than the healthy ones and the cocoon spun by the former was abnormal.

Xenopsylla astia, the indigenous commensal rat flea has been replaced by X. cheopis in many parts of India to a large extent. As a result of this replacement or suppression serious outbreaks of plague had occurred in the country in the earlier part of the century. The introduction of DDT for malaria control programme, as a collaboral benefit, has also served to control plague in the country. This has also encouraged DDT resistance in fleas. In the present paper the distribution of X. astia in the state of Maharashtra is discussed along with its susceptibility status to DDT. The distribution of this flea now appears to be patchy, being restricted to very few areas. The flea demonstrates high degree of resistance to DDT.

Seven benzyl-1,3-benzodioxole analogs were tested for possible effects on reproduction in females of the Mediterranean fruit fly. Single topical doses of J2581 (5-ethoxy-6-[4-methoxyphenyl]methyl-1,3-benzodioxole) and J3263 (5-methoxy-6-(1-[4-ethoxyphenyl]ethyl)-1,3-benzodioxole) were found to cause a temporary delay in ovarian growth in female medflies by 9 and 13 days respectively when compared to acetone-treated controls. Continued exposure of the analogs at the target site(s) appears to be necessary for more permanent effects. Nurse cell development appears not to be affected, but oocyte growth and subsequent egg production and egg hatch were significantly reduced. Methoprene treatment appeared to obviate the effect of J2581 in arresting ovarian growth.

Six cowpea cultivars, TVu 1890, TVu 1, TVx 3343-03E, IT82E-9, VITA-3 and Ife Brown, with different responses to infestation and damage by pod-sucking bugs (PSBs) were studied for the biophysical and biochemical characteristics of pod that may be involved in this differential response to feeding by PSBs. Tough pod wall, requiring a force of 25 newtons/mm2 to penetrate at pod maturity, is considered to be an important factor contributing to the lesser PSB feeding damage observed in the cultivar TVu 1890. The phenolic content of the pods of the studied cowpea cultivars was not correlated with their tannin content. Furthermore, no correlation could be established between the tannin content in the pod and the level of susceptibility of the cowpea cultivars to infestation and damage by PSBs. While tannins are considered to be important in conferring certain types of anti-herbivory properties to a number of plants and crop varieties, our findings suggest that in the cowpea cultivars studied, phenols in addition to the tough pod wall may be more important in conferring resistance to PSBs.

Economic injury level (EIL) by the sorghum earhead bug was estimated for nymphs, feeding adults and ovipositing adults of sorghum earhead bug, Calocoris angustatus Lethierry, using malathion or hexachlorocyclohexane (HCH) as insecticidal control measure. EIL varied according to the insecticide used and the stage of the insect. EIL per panicle was 7.9 nymphs, 5.4 feeding adults or 0.06 ovipositing adults when HCH was used, which increased to 15.1 nymphs, 10.5 feeding adults and 0.12 ovipositing adults when malathion was used for control.

Laboratory-reared tsetse, Glossina pallidipes were inoculated with the tsetse virus by microinjection into the haemocoel, and feeding through micropipettes. The inoculated tsetse were reared on rabbits for 45 days, and feeding, flight and mating activities recorded. The tsetse were dissected and the conditions of the salivary glands and gonads noted. In males, tsetse were examined under a compound microscope and the presence of spermatozoa noted. F1 pupae were allowed to emerge, dissected, and the salivary glands examined for hypertrophy, and the gonads for sterility.

There was no reduction in the activity of inoculated tsetse. Infection level was 23.5% in the treated adults. All infected ♂♂ were sterile while ♀♀ were fertile. There was no significant difference in the maternal age at larviposition, F1 pupal weight, or incubation period of F1 pupae, between treated and untreated tsetse.

A high proportion of F1 adults (65%) were infected, with category four hypertrophied salivary glands. All males with enlarged glands were sterile. The evidence obtained shows that the tsetse virus may be used in biological control of G. pallidipes.

The number of instars in the silkworm Anaphe venata was determined using three methods namely: (1) direct observation of cast exuviae by larvae reared through the entire larval stage, (2) use of frequency distributions of head capsule lengths and widths taken from larvae representative of the entire larval stage of the species and (3) morphological observations and examinations of larval segments and anal plates. Seven instars were observed for A. venata. The most reliable method was the direct observation of cast exuviae by larvae reared through the entire larval stage. It is further suggested that either the method of histograms of head capsules or examination of larval segments and anal plates be used to supplement this method for better reliability.

The intensity of damage to sorghum panicle caused by the sorghum earhead bug, Calocoris angustatus Lethierry (Heteroptera: Miridae) was studied under laboratory and field conditions. Laboratory studies showed that among the five nymphal instars, fourth instars consumed maximum food (5.06mg/day). In adults, the consumption was thrice that of the fourth instar nymphs. Male and female consumed on average 250.68 and 305.56 mg of food respectively from their second instar nymphal stage till their death. In the field, 1–3 days old panicles were preferred for oviposition when compared with panicles at later stages. Grain weight losses upto 31.54 g/panicle infested with three adults were recorded. Similarly the grain weight per panicle decreased as the number of ovipositing females increased; grain weight losses of 9.72–42.02 g were recorded.