The millet stem borer, Acigona ignefusalis Hampson, can cause total crop failures when severe infestations occur such as happened in northern Nigeria in 1984. Research at the Institute for Agricultural Research at Samaru has shown that various millet types and varieties exhibit different levels of susceptibility to the stem borer, although no resistant varieties are yet available. Infestation and damage by the stem borer are strongly influenced by date of planting and rate and time of nitrogen fertilizer. The effect of mixed cropping with sorghum depends on the spatial arrangement of the component crops in the mixture as well as on the insect population pressure. Systemic insecticides, particularly granular carbofuran, have been found to control the stem borer more effectively than contact insecticides like carbaryl. Seed dressing with carbofuran has been found to be ineffective. Some natural enemies of the stem borer have been identified but their role in lowering damage to millet is minimal. The destruction of infested stems before the beginning of the rainy season is a very important control measure against the insect. The possibilities of integrating these various methods for stem borer control are discussed.

A study of the mosquito fauna of the Mwea Rice Irrigation Scheme, Kenya, carried out during 1984 and 1985 identified 13 species, with Anopheles gambiae s. l. comprising 65.71% of the total collection. X-chromosome identification of 652 semi-gravid females resulted in 649 (99.5 %) positive identifications of An. arabiensis, implicating it as the noxious member of the An. gambiae complex present. Inversion polymorphism of chromosomes 2Rb and 3Ra karyotypes was studied in one village population. Seasonal population changes were found to be heavily dependent on rice field surface water. Artificial irrigation for rice farming greatly extended the breeding period per year by linking up the two wet seasons. Adult females fed more frequently on bovids than humans. The mean percentage gonotrophic condition of all females caught in the villagesof Karima, Thiba, Mucii-wa-Urata and Rurumi by pyrethrum spray-sheet collections, miniature light-traps and exit window traps was 69 % bloodfed, 18 % unfed and 13 % gravid. These proportions were statistically shown to be within predictable limits over time and space. The sporozoite infection rate in adult females was 0.55% by manual dissections and 1.2% by the ELISA technique.

Quality assessment and control of artificially reared insects has been traditionally linked to how well the insects perform in their “intended role” or their “fitness for use”. This paper suggests that quality should be defined more in terms of success in survival and colonizing ability. It is argued that the rearing facility should be regarded as an “ecological habitat”. Differences between wild and artificially reared insect populations are therefore due to the different effects and demands placed on the insects by the two habitats. Assessment of quality and its subsequent control should be based on biological parameters that are constant in the two habitats like the larval critical weight (Lcw).

Biological and morphometric studies of the different stages of Lucilia caesar, were carried out using three rearing media prepared from local materials as the test media, and the standard Snyder's medium as control. The materials for the test media were: (i) Garri, soybeans, palmwine and liver (GSPL), (ii) Garri, soybeansand palmwine (GSP) and (iii) Pap, nono, cabbage and liver (PNCL). The Snyder's medium consists of milk, yeast and bacto agar (M Y A). There was no significant difference in the duration of larval instars and adult emergence for the blowflies reared in the standard, PNCLand GSPL media. For blowflies reared in GSP, duration of larval and adult stages was prolonged by about 48 hr and 5 days respectively, when compared with the flies reared from the other three media. The average length and width of each larval stage reared from the four media were not significantly different. Morphometrics of the adults showed that those reared from the GSPL and control media were longer, heavier, and laid significantly more eggs per female than adults reared from PNCL and GSP media. The GSPL medium was considered to be the most suitable alternative to MYA.

Oils from the seeds of neem, Azadirachta indica A. Juss and from a brown pepper, Piper guineense Schum and Thonn afforded protection to cowpea seeds from Callosobruchus maculatus infestation beyond 3 months. Insecticida! efficacy was higher with Piper seed oil (PSO). At 24 hr after surface treating cowpea seeds with 2 and 3 ml/kg of PSO, bruchid mortality reached 100 %, but with neem seed oil (NSO), mortality was 65–100% at 3–5 days. Oviposition in control averaged 60.75 eggs, 49.5 eggs in NSO and 15.5 with PSO. Reproductive efficiency (RE) of PSO-treated females was nil, and very low (1.7 to 2%) with neem oil, but high in control confirming adverse ovicidal effects of both oils. Piper oil prevented emergence of F1 bruchids and neem oil prolonged their mean development period over the control. Neem oil reduced seed damage by 94.67%. Because Piper seeds are a condiment in some Nigerian dishes, and are also used therapeutically in many traditional diseases, there may be no toxicity. However, yield of PSO is much less than that of neem from an equal weight of seeds extracted with organic solvents.

Various stages of Dermestes maculatus DeGeer were placed in specimen jars in contact with dried Tilapia fish treated separately with 0.25, 0.50, 1 and 2 g of neemseed powder per 25 g of fish. Neem powder significantly inhibited oviposition and killed the adults. Neem has no ovicidal action, but incubation period was prolonged. In treated fish, larvae did not develop beyond the second instar and 93 % of larvae died by day 30. Minimal frass was produced in treated fish. The aesthetic attractiveness of the fish was high.

The relationship between corpus allatum (CA) and prothoracic gland (PG) activities has been examined during postfeeding larval and prepupal stages of en-silkworm, Philosamia ricini (Dru.). Using the isolated larval abdomen technique, the critical period of ecdysone (MH) was determined. It was 114 hr immediately after the beginning of cocoon spinning at 20 ± 2°C. To study the CA activity a histometric method was used. CA volumes suddenly increased at the prepupal stage. From these data a clear positive correlation between CA and PG activities was recognized.

Brainless Ph. ricini pupae, a highly reliable bioassay organism for detecting prothoracicotropic (PTTH)-like effects, were produced. The debraination of Ph. ricini larvae after the critical period of PTTH, produced brainless pupae. This bioassay organism was used for studying the action of juvenile hormone (JH) and MH in the metamorphic endocrine centres during the absence of the brain.

Injection of 5 μg altozar (JHA) into debrained Ph. ricini larvae accelerated pupation (12.24 ± 0.36 instead of 16.51 ± 0.19 days). Moreover the produced brainless pupae moulted to second brainless pupae. The injection of 5 μg JHA into brainless pupae or isolated larval abdominae of Ph. ricini did not show any effects. Brainless Ph. ricini moths were obtained after injecting the brainless pupae with MH (10 μg-40 μg/p). The injection of high concentrations of MH (≥ 70 μg/p) into brainless pupae activated the CA and produced pupal-adult intermediates. The present data reveal that the PTTH at low concentrations, permits the action of a JHA in the PG. Also it shows that the MH at high levels activates the CA.

The striped mealybug, Ferrista virgata (Ckll.) has become a very serious pest of guava in India. Since the insecticides are ineffective, an attempt was made to suppress F. virgata with an introduced coccinellid, Cryptolaemus montrouzieri Mulsant C. montrouzieri and other local natural enemies especially Aenasius advena Comp. and Scymnus coccivora Ayyar effectively controlled F. virgata in guava orchards.

The development and pest status of Aspavia armigera on two cowpea varieties viz: Ife Brown and TVU1890 and alsoon two upland rice varieties viz: ITA 128 and ITA 257 were studied under ambient conditions in the laboratory and at the roof-top garden, Department of Agricultural Biology, University of Ibadan, Nigeria.

The oviposition periods on rice were 15.1 and 6.0 days respectively on ITA 257 and ITA 128; and on cowpea 10.6 and 8.5 days respectively on Ife Brown and TVU 1890. Fecundity was low. Mated females laid the highest number of eggs (24.6) on the cowpea Ife Brown and this was significantly higher than in the other cultivars. Mated and unmated males and females lived longer on Ife Brown and ITA 257 than on ITA 128 and TVU 1890.

The developmental period (nymph to adult), was shorter on ITA 257 (23.3 days) and Ife Brown (22.9 days) than on ITA 128 (23.3 days) and TVU 1890 (25.3 days). There were five nymphal instars and the mean growth ratio of head capsule measurements was 1.32.

Infestation at the level of two A. armigera per peduncle caused total seed losses in the two cowpea varieties whereas four and eight bugs per panicle caused 39.1 and 31.7 % grain yield losses in ITA 257 and ITA 128 rice varieties respectively.

The structural components and physical characteristics of sorghum kernels were studied as factors of resistance against Sitotroga cerealella (Oliv.) and Sitophilus oryzae (L.). Specifically, the effects of kernel glumes, weight, size and hardness on larval entry site, oviposition site, emergence site, progeny production, and kernel damage and weight loss, were investigated. The larvae of S. cerealella entered kernels primarily in the germ end and its periphery. Females of S. oryzae oviposited eggsmainly in the endosperm portion of kernels. Larval entry into kernels, and subsequent development of S. cerealella was enhanced in kernels that were enclosed by glumes. In addition, S. cerealella caused greater damage and weight loss in kernels with glumes. In contrast, kernels with glumes yielded less adult progeny of S. oryzae, and sustained less kernel damage and weight loss. The emergence holes of S. cerealella were located mainly in the crown end, whereas those of S. oryzae were mostly in the endosperm portion of kernels. The heavier and larger kernels produced heavier and larger adult progeny of both species of insect.

The developmental periods of the immature stages of Exochomus troberti Mulsant were studied in the laboratory at the prevailing temperature range of 26–30°C. That of the second instar larva was the shortest (2.1 days) followed by the third instar larva (3.1 days). The longest developmental period (approximately 5 days) was recorded for the egg, first- and fourth-instar larvae and pupa.

Oviposition commenced after 1 week of adult life and peaked in the 5th week with 37.2 female eggs/female. All ovipositing females survived the first 9 weeks of adult life when 82% of the total eggs were laid. By the 13th week, which was the effective end of reproduction (98 % fecundity) only 40% of the females had died.

Both capacity for increase (rc) and intrinsic rate of increase (rm) were calculated for E. troberti and found to be 0.092/day and 0.105/day, respectively.

Mean daily predation rates in non-choice experiments on the second instar nymphs of P. manihoti by the fourth, third and second instar larvae of E. troberti were 28.3, 15.6 and 8.0, respectively. On the third instar nymphs and fourth instar young adults of P. manihoti the mean daily predation rates by the fourth, third and second instar larvae of E. troberti Were 17.6, 8.3 and 4.5; and 4.0, 3.0 and 1.0, respectively.

The populations of E. troberti, other coccinellid predators and P. manihoti were monitored in two small local farms for three seasons. E. troberti was found to be the dominant coccinella predator in terms of numbers of individuals found in the field during the years of this experiment.

The cyclical population oscillations of P. manihoti were similar in all the experimental years but differed only in the amplitude of oscillations. Those of E. troberti and the other coccinellid predators were lower than those of P. manihoti.

There were significant variations in oxygen consumption and carbon dioxide evolution of Macrotermes carbonarius (Hagen) among the soldiers and workers over a 10-hr experimental period. This suggested that the insects exhibited rhythmic respiratory behaviour in spite of being separated from their nest system and in the stressful situation of confinement of a respiratory flask at 29°C. The correlation between body fresh weight (mg) and respiratory rate ml O2/mg fresh wt/hr was significant. A respiratory quotient of 1.0–1.1 suggested that glucose was the respiratory metabolic substrate utilized and that both aerobic and anaerobic processes could have been taking place. Most of the leaf litter imported into the mound was utilized by the fungus on the fungus comb for metabolism with the release of carbon dioxide, heat and water. The heat released was sufficient to maintain the brood chamber temperature at 29.1 ± 03°C despite fluctuations of the ambient temperature and the temperature of the surrounding soil.

Spraying of diflubenzuron at 100 g a.i./ha after spike emergence (10–15 cm from flag leaf) was more effective against early larval stages of millet spike worm, Heliocheilus (=Raghuva) albipunctella De Joannis, than spraying the crop at female flowering or at the milky grain stage.

The life cycles of two phycitid moths, Plodia interpunctella (Hubn.) and Ephestia cautella (Wik.) were studied under ambient laboratory conditions on groundnut, maize, sorghum, wheat and standard medium (maize/wheat/glycerol, 8:8:1, w/w). Egg hatchabilities were found to be 98.6 and 91.6% for P. interpunctella and E. cautella respectively. Five larval instars were recorded for each species based on head-capsule width measurements. The growth ratios of the larval head-capsule width ranged from 1.08–1.72 in P. interpunctella: and 1.33–1.57 in E. cautella. These ranges fall within the acceptable range in Dyar's rule. Mean fecundities ranged from 96.83 ± 0.31 on wheat to 190.87 ± 0.47 on standard medium for P. interpunctella; and 96.83 ± 0.31 on groundnut to 192 ± 1.33 on standard medium for E. cautella. Mean developmental periods of the two moths on the selected food media ranged from 25.65 days on standard medium to 46.11 days in broken wheat for P. interpunctella; and 26.95 days in broken sorghum to 40.14 days in ground maize for E. cautella.

Larvae of Maruca testulalis were found to be randomly dispersed on flowers of cowpea cultivar Vita 1. Three models based on Taylor's power law, Lloyd's mean crowding and the negative binomial were tested to find out the best fit for developing a sequential sampling plan for this pod borer. Taylor's power law model gave the best fit whilst the negative binomial gave the least. A sequential sampling plan and a table of optimum sample size for use in the field were therefore developed, based on the random distribution.

The susceptibility of head lice, Pediculus humanus capitis collected from children in Israel and that ofa laboratory colony of body lice, Pediculus humanus humanus to the insecticides malathion, deltamethrin, permethrin, fenitrothion and dieldrin has been evaluated using standard WHO papers. The LT50 and LT95 were established using different exposure times. Deltamethrin had the highest“knock-down”effect, followed by permethrinand malathion. All insecticidesexcept dieldrin gave higher mortality for body lice than for head lice. No differences in the susceptibility between adult and nymph lice could be observed.

Some aspects of the biology of Callosobruchus subinnotatus (Pic) were investigated at controlled conditions. Temperature and relative humidity were found to have effect on oviposition, development and longevity of adults. The best condition for oviposition was 30°C, 80% r.h. at which the mean number of eggs laid was 135.8 and the worst condition was 35°C, 50% r.h. at which 61.1 eggs were laid per female. Oviposition lasted very long at 25°C and was too short at 35°C. Relative humidity favoured oviposition at 30 and 35 but not at 25°C. The beetles were found to be positively phototactic as more eggs were laid at 12 hr light and 12 hr dark (105.1 eggs) and continuous light (98.6) than at continuous darkness (43.0).

Duration of development was shorter at 35°C than at other temperatures investigated. The shortest developmental period was at 35°C, 80 % r.h. (23.2 days) while longest was at 25°C, 50 % r.h. (42.6 days). While development was shorter at 35°C, more progenies were produced at 30°C and the rate of increase was better enhanced at 30°C. Adults were heavier when reared at lower temperatures and high humidities than at high temperatures and low humidities. Adults lived longer at lower temperatures and high humidities than at higher temperatures and lower humidities. The females were heavier and lived longer than the males.

Several experiments were conducted with Rhipicephalus sanguineus, Dermacentor variabilis and Amblyomma maculatum during which degrees of resistance by rabbits to infestation were quantified. Manifestations of resistance were measured through estimations of “Decreased Tick-Weight Index”, “Decreased Engorgement Period Index” and “Reject Index”. Degree of resistance was evaluated through estimation of Tick Resistance Index. The degree of resistance of rabbits to infestation with each of the three tick species was found to increase with the number of reinfestations. Fully engorged ticks induce the same degree of resistance as partially engorged ones. Nymphal ticks induced higher resistance than larvae, but the resistance conferred by both immature stages was lower than that conferred by adults; previous exposure of rabbits to adults enhanced the degree of resistance against subsequent nymphal or larval infestation. There was cross-resistance between A. maculatum, D. variabilis and R. sanguineus. Resistance induced in rabbits waned with time; rabbits became non-resistant to ticks 12 weeks after the last infestation. Resistance to tick infestation was transferred to rabbits through passive transference of serum from resistant animals. The importance of these observations to the epidemiology of field infestation of animals with ticks is discussed.

Laboratory studies were carried out to determine the effect of high larval densities of Plodia interpunctella (Hubner) on the development and survival of the moth in two food media. Mortality was found to be higher when reared on groundnuts than on artificial diet. Mortality was between 6.6 and 13.3% when larval densities were below five larvae on 3 g of both groundnuts and the artificial diet in 75 × 25 mm tubes. At higher larval densities (10 or more larvae on 3 g of medium) mortality ranged from 22.5 to 60% on the artificial diet, and on groundnuts it was between 30 and 65%. In both media, development period was prolonged and weights of moths at emergence was lower when larval densities were greater than 10 per tube.

When high densities were experienced between the first and the fourth instars individuals had protracted development, high mortality at larval stage and reduced weights of emerged adults and those subjected to high densities only at the final instars were less significantly affected. It seems that the fourth larval instar is the stage most sensitive to high densities.