At 25°C and 70% r.h. larvae of Spodoptera exempta develop faster and pass through five instars on star grass, Cynodon dactylon (L.); Pers. maize, Zea mais L.; and Kikuyu grass, Pennisetum clandestinum Chiov. whereas on guinea grass, Panicum maximum Jacq.; and Setaria plicatilis (Hochst.) Hack, the development is not only slower, but the larvae pass through six and seven instars, respectively. Samples of larvae reared on the former grass species suffer high mortality only at the first and the last instar stages so that the distribution of per cent mortality is U-shaped. On the latter host plants, the mortality during the first instar stage is equally high and continues through the subsequent instars with no obvious peak towards the end of the larval life. The samples on C. dactylon and Z. mais had much higher growth indices than those on P. maximum and S. plicatilis. C. dactylon is a preferred natural food plant of S. exempta in the field, and these investigations demonstrate its value and importance.

Journal citations in Bibliography of entomological research in Nigeria: 1900–1973 were subjected to Bradford analysis with the view of evaluating the completeness of the bibliography and determining the core journals and core authors. As to the completeness of the bibliography, it was inferred that the bibliography is 93% complete in terms of journals and 84% complete in terms of articles. On further testing the law for its applicability on author distribution, it was observed that the observed value for total number of authors was just a little above 50% of the actual figure. This may suggest that as in a similar study Bradford's law may not be as applicable to author distribution as it is for literature although the verbal formulation of the law has been found to be applicable to users distribution of periodical literature in a library. On the other hand, the investigation revealed that only three journals (i.e. 1.4% of the total number of 216 listed in the bibliography) form the core, while out of 650 authors, 21 constitute the core. The analysis also reveals an interesting phenomenon with the parameters (a measure of subject breadth being negative).

A comparison of the metabolic rates of different castes and instars was estimated by measuring the biological half-life of the radioisotope I131. The metabolism in the soldier caste was not only higher than alates and dealates, but also pre-soldiers. The rate of metabolism increased with an increase in the age of the nymphs. The termites which were provided with food had slow metabolism compared to those kept under starvation. The studies are helpful in understanding the phenomenon of ‘temporal polyethism’ among termites.

Both free and sessile haemocyte counts in Alphitobius piceus showed wide variations between 06.00 and 22.00 hr. Variations in the haemogram appeared to be related to sex related cycles of activity, presumably with special reference to feeding patterns. Males showed higher total haemocyte counts during the day in comparison to females. In both sexes, the percentage of prohaemocytes and spherule cells and only in males, plasmatocytes increased during the early hours of night. In females, the percentage of granular haemocytes decreased notably between 18.00 and 20.00 hr. Number of adipohaemocytes and oenocytoids did not vary significantly. Heat treatment caused release of sessile haemocytes into the circulation resulting in a notable increase in total haemocyte counts during the day. This increase was comparatively high in females in comparison with males. Altered photoperiod had little effect on these haemocyte variations. Blood volume was slightly higher in the night than in the day in both sexes. The variation of blood volume was insignificant under both heat treatment and altered photoperiod conditions.

The serpentine leaf-miner Liriomyza trifolii is a new proliferous and polyphagous agricultural pest in Mauritius, attacking crops, ornamentals and weeds. Urgent chemical control measures had to be developed in order to save total crop loss, in particular potato, tomato, haricot beans, crucifers and onions. This insect is resistant to most insecticides. In view of formulating an integrated management programme, this paper reports on some aspects of practical importance concerning the biology and ecology of the leaf-miner, the incidence of damage, and the possibility of its control by natural plant products such as extracts of neem (Azadirachta indica). Steam distillates of neem leaves seriously affect larvae and pupae upon treatment by contact at as low a dose as 0.3% of the extract. Field treatments of onion plantations with aqueous neem extracts (0.5%) gave good protection to the crop. The current control measures are briefly considered.

Seed yield loss was independent of the eggs laid on and damage to the buds, flowers and pods by the larvae of the borer, Adisura atkinsoni Moore at the 0.05% level. Loss in seed yield was dependent on seed damage. Seed damage, thus can be used to precisely locate a borer resistant Lablab niger cultivar, but in an already pre-selected germplasm.

This paper briefly discusses insect pest responses in mixed crop stands, their peculiarities and possible crop protection advantages. Results on the effects of a bean–oat diculture on the movements and feeding activity of the adult pea leaf weevil, Sitona lineatus L. are presented and discussed. Mixtures of these crops were found to significantly reduce the amount of notching of the bean leaflets by the weevil and weevil relative populations are compared to the sole bean crops, and to increase emigration from the more diverse plots.

Bruchidius atrolineatus appears at the end of the rainy season when pods of its host plant Vigna unguiculata begin to mature. The eggs are deposited along the ventral suture of pods in the vicinity of the seeds. When the eggs are not attacked by Trichogrammatidae their larvae penetrate the seeds and mortality is low during the post-embryonic development. Most of the adults emerging at pod maturity have functional reproductive organs. In that case the females laid on the same mature pods and larvae develop inside the seeds during the first part of the drying season characterised by high diurnal temperature and low relative humity. If the first emerged adults have functional reproductive organs, the following (60% of the population) are in reproductive diapause. Such diapausing insects have been found during the dry season in shelters near the cultivated fields of Vigna unguiculata. Induction or termination of this reproductive diapause are not yet studied. This diapause probably allows the maintenance of populations during the dry season in absence of host plant.

The relationship between seasonal numbers of outbreaks of African armyworm (Spodoptera exempta) in Kenya and Tanzania, and early season rainfall in source areas has been examined using records for 21 seasons. Significant inverse relationships were found between numbers of Kenya outbreaks and early season rains in the Kisumu area, and between numbers of Tanzania outbreaks and early season rains in the Morogoro and Mtwara areas. Total Kenya and Tanzania outbreak numbers were significantly inversely related to early season rainfall for 8 areas combined. These results suggest that early season rainfall totals, either from specific likely source areas or countrywide, could be used in January to give a seasonal forecast of likely numbers of armyworm outbreaks during the rest of the season. Seasons with more than average numbers of outbreaks often follow poor early season rains and visa versa. Further work is needed to establish biological causes of this apparent relationship.