Progress in the development of a simple life cycle model, with both deterministic and stochastic components for the brown ear tick, Rhipicephalus appendiculatus Neuman (Acarina: Ixodidae), is described. Control strategies or interventions that are user-manipulated are incorporated.

The model is initially applicable to Rusinga Island, Lake Victoria, Kenya, where parasitic phase data have been accumulated for a 30-months' period, but could be used for any other R. appendiculatus locations.

Some properties of the gut amylase of Sophrorhinus insperatus Faust have been studied. The enzyme has maximum activity at pH 5.0 and 45°C. It is activated by C−, Ca2+ and Cd2+ tons and inhibited by Cu2+ and Hg2+ lons. Low Michaelis constants of 0.26 mg/ml and 032 mg/ml were obtained for the larva and adult gut amylases. Enzymatic activity was found to be consistently higher in the larva than in adult stage, probably suggesting the larval stage as the most destructive stage. Extracts of Cola nitida (Vent) Schott and Endlicher and C. acuminata (Pal de Beauv) Schott and Endlicher, inhibited amylase activity in vitro at varying magnitudes. The higher level of inhibitors in C. acuminata is an index of its low susceptibility to weevil attack both on the field and at storage.

Mature (5- to 6-day-old) male and female pupae of C. partellus were irradiated at 5 to 20 kilo-Roentgen (kR) and 5 to 10 kR respectively. Emergence of normal appearing moths, pupal periods and adult longevities remained statistically unaffected. Fecundity of normal (nonirradiated) females mated with males irradiated as pupae was nonsignificantly different from control, but fecundity of females irradiated as pupae at 10 kR was significantly reduced when they were mated with normal mates. Dominant lethals of varying intensities were induced at 5–20 kR. However, induction of dominant lethality was sex- as well as dose-dependent. Radiation doses inducing 100% dominant lethals in sperm (20 kR) and ova (5 kR) did not mitigate the mating ability of males and receptivity of females. However, receptivity of females was reduced significantly when they were irradiated as pupae at 10 kR. Rates of embryonation in F1 eggs were significantly reduced when normal females were crossed with males irradiated as pupae at 20 kR, but similar effect was observed at 10 kR in reversed crosses. Embryonic development was delayed in eggs obtained from crosses, where male or female parent was irradiated in pupal stage, but in both cases most of the dominant lethals acted late in embryonic development.

Polyacrylamide gel electrophoresis was carried out on Nephotettix virescens (Distant) adults collected from India, Sri Lanka and the Philippines, and maintained in glass-houses on rice variety TN-1 at the University of Wales, Cardiff, United Kingdom. The following enzymes showed activity and were recorded: acid phosphatase (ACP), a-glycerophosphate dehydrogenase (aGPD), fumarase (FUM), glucose-6-phosphate dehydrogenase (G-6-PDH), glutamate dehydrogenase (GLUD), glutamate oxalo-acetate transaminase (GOT), hexokinase (HK), lactate dehydrogenase (LDH), malic enzyme (ME) and xanthine dehydrogenase (XDH).

The bands in nine enzymes were homologous across the three populations and showed no differences.The relative mobility of the enzyme GLUD in the Philippines population was lower than in the other two populations and could be used for diagnostic separation.

The results confirm previous reports of differences in the relative mobility of esterase bands of the Philippines population of N. virescens from India and Sri Lanka populations on starch gel.

Four calves were infested with larvae of Boophilus decoloratus and Boophilus geigyi on three successive occasions, at 30-day intervals. Results show that the attachment of first instar larvae and survival of subsequent developmental stages (AS), duration of feeding (DF), weight of engorged ticks (WT) and oviposition by engorged ticks were significantly affected when the calves were infested for the second and third time at 30-day intervals with the ticks larvae. After the third infestation, AS was reduced by 48.6%, DF increased by 15.6%, WT and oviposition were reduced by 83.8 and 81.5 %, respectively for B. geigyi. The respective data for B. decoloratus were 48.8, 173, 91 and 80.9%. The tick resistance index (TRI), showed significant reduction to a mean of 0.14 in B. geigyi and 0.076 in B. decoloratus.

The data suggest development of immunity in calves by the first cycle of infestation, inducing resistance against the ticks, which were manifested in subsequent infestations. The use of tick-immunization of cattle for the management of ticks in Nigeria is suggested.

Tropical African ticks are found on their hosts throughout the year, but at varying infestation levels. These population changes, for most of the time, have been associated with climatic changes. Their development is inversely related to temperature. Several workers reported that development failed for a number of tick species at temperatures below 15°C, suggesting a possible lower temperature threshold for tick development. The upper development limit for most of the tropical rhipicephalids appear to be 37°C.

Ticks are particularly susceptible to attack during lethargic pre-moulting and the weak post-moulting period. Many biological features enable them, however, to survive especially well. They lay numerous eggs and withstand a comparatively wide temperature and humidity range with greater ease. They survive for months or years without food.

Their degree of host specificity varies from genus to genus or within subgroups of various genera. The requirement of two or more kinds of hosts often with divergent habits, limits their distribution to certain faunal areas.

This paper reviews our current knowledge on development and survival of ixodid ticks under tropical field conditions including some laboratory studies.

Bioassays against the fourth instar larvae of mosquito, Culex pipiens pipiens showed that the non polar part of the duck weed, Lemna minor extracts has a high insecticidal action. On the other hand, these extracts contained synomones of the duck weed which repelled the ovipositing females. By using concentrations equivalent to LC25, the survival resulting by the n. hexane was the least. The tolerance for the sublethal doses was associated with malformations in all stages. First instar larvae and recent pupae were more susceptible to the duck weed synomones than the other larval instars. The duck weed synomones repelled the ovipositing females of Piophila casei and have had an insecticidal effect on larvae and reduced resulting adults. When larvae of Spodoptera littoralis were subjected to sublethal doses of duck weed extract, malformations in the subsequent stages were found.

One of the critical factors in assessing maize lines for resistance to Sesamia calamistis is the number of larvae/plant used for infestation. Artificial infestation of maize plants with two and five larvae/plant resulted in 29.1 and 39.5% stand loss (dead hearts and stalk breakage), while 10 and 15 larvae/plant resulted in 52 and 72.9% stand loss, respectively. For a satisfactory artificial infestation in maize screening trials against the maize stem borer in Nigeria, a population level of 10–15 larvae/plant is recommended.

The systems analysis approach is an appropriate procedure for the effective development of a management model for the strategic control of ticks. The interacting nature of the controllable and uncontrollable factors, and the difficulty in mimicking such complex situations experimentally, should be considered in the formulation of such models. ICIPE's approach relies on the use of both deterministic and stochastic models, and assumes unambiguous definitions of management's expectations.

A system for developmental timing for Panstrongylus megistus and Rhodnius prolixus (Hemiptera: Reduviidae) adults is presented, using as a marker, the evolution of the cuticular tanning after ecdysis. In both species the setting of the cuticular pigmentation pattern after imaginal moult is a homogeneous process in population, i.e. no individual variations were detected. The system allows one to estimate the exuvial time up to 5 or 7 hr after occurrence. A preferential exuvial period (PEP) was determined in the population under usual rearing conditions by using this system. The PEP runs from 2100 to 0500 hr for P. megistus and from 0100 to 0800 hr for R. prolixus. These data are meaningful for endocrine studies on those species. Studies on PEP under natural environmental conditions would be useful for the control of Chagas' disease vectors.

The influence of the host plants tobacco, chilli and brinjal on the susceptibility of Myzus persicae (Sulz.) to five OP insecticides was assessed. The order of toxicity of the insecticides to the aphids on tobacco was monocrotophos > demeton methyl > dimethoate > methamidophos > acephate, on chilli; methamidophos = monocrotophos > demeton methyl = acephate > dimethoate and on brinjal, methamidophos = monocrotophos > acephate > demeton methyl = dimethoate. Among the five insecticides, monocrotophos had the highest inhibitory potency in vitro as indicated by I50 and ka values, followed by demeton methyl, dimethoate, methamidophos and acephate. Electrophoretograms of homogenates of aphids adopted to chilli and brinjal showed a higher activity of the detoxicating enzyme carboxylesterase than found in aphids on tobacco.

Selected aspects of ecological interactions with ticks, tick-borne diseases and their hosts are discussed in relation to Integrated Tick Management, The needs to preserve tick-borne disease enzootic stability and to ensure the economic justification for any interventions were emphasized.

Biochemical analysis of lakefly (chironomid/chaoborid mixtures and Povilla adusta samples) were conducted to determine their nutrient value and their potential as source of high quality nutrients in animal feeds. The results showed lakefly as rich in protein (62–67 g/100 g), fat (10 g/100 g) and ash (4–6 g/100 g). Moisture was low as was crude fibre. Povilla were richer in crude protein (67.4 g/100 g) and calcium (152 mg/100 g). The chironomid chaoborid mixture was however extremely rich in phosphorus (1.2 × 103 mg/100 g) and potassium (1.2 × 103 mg/100 g). Other trace elements were present in significant quantities as were niacine, thiamine and riboflavin. It is therefore deemed feasible to produce high quality nutrient concentrates from lakefly material for use in animal feeds. Further work Is however essential to determine lakefly digestibility and palatability and to ascertain suitable lakewide harvest techniques for the lakefly.

The effects of host age, age of Cotesia marginiventris Cresson adults and temperature on interspecific competition between fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larval parasitoids C. marginiventris, Microplitis manilae Ashm. and the egg-larval parasitoid, Chelonus insularis Cresson were studied. All parasitization results for C. marginiventris and M. manilae were from FAW larvae parasitized as eggs by C. insularis. The maximum reproductive potential for C. marginiventris was achieved in hosts initially parasitized by C. insularis and were 36 to 48 hours old and at a temperature of 25°C. No host discrimination was found for C. marginiventris between larvae containing a developing C. insularis and non-parasitized larvae. The optimum parasitoid age for C. marginiventris during the host exposure period was 48 to 96 hr. Younger or older parasitoids were not able to compete as successfully against C. insularis. A sex ratio of approximately 65% males was present in C. marginiventris progeny produced from parents ranging in age from 24 to 108 hr old. Egg to adult development times at 25°C were 17 and 26 days for C. marginiventris and C. insularis, respectively. In multiple parasitized larvae, C. marginiventris appeared to physically attack and destroy the larvae of C. insularis. However, M. manilae larvae died after 6 days without appearing to have been physically attacked in hosts containing C. insularis.

Artificial diets were formulated and evaluated for their suitability to rear the spotted bollworm, Earias vittella, a major pest of cotton and okra. The most satisfactory diet consisted of maize semolina 11%, wheat bran 4.6%, soybean powder 2.4%, yeast 1.4%, salt mixture 0.9%, ascorbic acid 0.3 %, cellulose 0.9 %, agar 1.8%, water 76.7% and preservatives. The insect was reared on this diet for 10 generations without any adverse effect on its development and reproductive potential.

Investigations on temporal distribution of Bemisia tabaci (Gennadius) was carried out on 14 weeks old cotton genotype, RAS 299–1, during 1987–1988 at Raichur (Karnataka). Oviposition was restricted mainly on the leaves of the youngest branches. Highest egg load of 89.16 per sq cm was recorded on youngest leaf of terminal host branch. Nymphal and pupal population was more on the middle leaves than on extreme leaves and followed a normal curve in their distribution. Adults exhibited similar trend in distribution to that of the egg stage.