About 20 species of borers are rice pests. Of these, five—yellow borer, striped borer, white borer, dark-headed borer, and pink borer—are of economic importance. Yellow borer and striped borer occur most widely in Asia and cause serious yield losses.

Varietal resistance to these two species has been investigated during the last 30 years. Field and greenhouse screening techniques have been developed and numerous germplasm entries have been evaluated for resistance. Several hundred varieties with low to moderate levels of resistance have been identified. Except for several wild species of Oryza, germplasm with a high level of resistance has not been found.

Information available to date indicates that the resistance is under polygenic control. Moderate levels of resistance from several donor parents have been incorporated into improved varieties. Some of these moderately resistant varieties, for example, IR20, IR36, IR50, Ratna and Chandina, are widely grown and play an important role in integrated pest management programs for stem-borer control. Efforts to develop cultivars with levels of resistance higher than presently grown varieties are under way using the diallel selective mating system and the male sterile facilitated recurrent selection schemes.

Field data of counts of eggs and larvae of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) in 12 uncultivated plants in Tolima, Colombia, were used to conduct analyses of variance of the relative importance of the 12 for the insect. Analyses were based on the number of eggs and larvae found per terminal and per 5 g of terminal material of each host.

Regardless of the analysis, more eggs and larvae of H. virescens were found on Desmodium tortuosum (Sw) DC (Papilionaceae) than on the other 11 hosts. In general, more eggs were found on pubescent plants, especially those with glandular trichomes.

A relatively high ratio of larvae:eggs for Ipomea triloba L. (Convolvulaceae) was interpreted to mean that larvae of H. virescens migrated to this plant from eggs laid on other hosts.

The removal rate of eggs from seven hosts due to unknown reasons was estimated to differ between the seven.

Seasonal incidence of the sorghum earhead bug, Calocoris angustatus Lethierry, was studied by sowing the crop once in 10 days, throughout the year during 1978 and 1979, as well as by sowing it at fortnightly intervals from early “kharif” to late “rabi” during 1979. The bug was found throughout the year except for a few weeks during March, April and May. The milky stage of the earhead was the most preferred stage compared to pre-flowering, a third flowering, flowering and ripening stages. The adults dominated during pre-flowering and a third flowering stages whereas nymphs dominated during milky and ripening stages. The computed seasonal indices were higher during August (230), September (222), October (224) and January (215) which coincided with blooming and milky stage of sorghum in general fields. Correlation studies between the bug population at the milky stage and maximum temperature indicated negative and significant (r = -0.2967) relationship, and positive and significant (r = +0.2727) relationship with relative humidity. Low incidence of bugs was observed on the crop sown during June.

Twelve cultivares were grown along with released high yielding hybrid CSH-1 (susceptible to stem-borer) to investigate their relative resistance to stem-borer at three locations. Results obtained have established that the 12 cultivars possess moderate levels of resistance to stem-borer. The damage suffered by them was significantly lower than CSH-1. Further, four cultivars viz. E601, E 602, E 603 and E 604 suffered less damage.

The stability of the resistance was worked out by following the model of Eberhart and Russell (1966) [Crop Sci. 6, 36–40]. The means of various cultivars were calculated and regression coefficients (bi) were tested against unity to locate most adaptable cultivar for borer damage. The cultivar × environment interactions for leaf injury and stem tunnelling (two parameters used for assessing stem-borer damage) were significant and in most of the cases were due to linear response of different cultivars. Cultivar E 601 proved to be most promising and stable for resistance to stem-borer.

The termite Macrotermes subhyalinus (Rambur) builds large earthen mounds of many different types, two of which are described in detail here. As far as is known at present, the two types occur in different areas. The main difference is in the ventilation system. In one, the Bissel type, there are many holes connected up inside the mound in such a way that external air is drawn through the passages and cools the interior of the mound. The other, the Marigat type, has only one large opening raised to a considerable height above the ground so that air is drawn out at the top, and drawn in from the surrounding soil through underground foraging passages.

Seven species of mosquitoes oviposited in open and bored bamboo traps at a site in Peradeniya, Sri Lanka, the most prevalent being Aedes albopictus, Aedes novalbopictus and Armigeres subalbatus. These three species preferred to lay in open than in bored traps. Aedes albopictus and Ar. subalbatus preferred to lay at ground level but Ae. novalbopictus showed no preference between ground level, 3.5 and 7.0 m height. A comparison of two collection series, one with traps in fixed positions and the other with traps interchanged randomly with respect to the positions, showed that individual trap attractiveness is a factor that can have a marked influence on the overall oviposition trends in Ae. albopictus and Ar. subalbatus.

A study of oviposition with respect to height above the water level showed that in Ae. albopictus and Ar. subalbatus, more than 75% of the eggs were laid within about 16 mm of the waterline. However, there was a markedly greater dispersion of eggs in Ae. albopictus, indicating more vertical movement during oviposition in this species than in Ar. subalbatus.

Full-grown pupae Agrotis ipsilon were irradiated with 5 or 10 krad and crossed with unirradiated female. The F1 progeny were more sterile than parents. Percentage of mated female of F1 was greatly reduced while the mating frequency was increased. Less inseminated females were among the F1, particularly when the female inherited the sterility. The mortality among larvae of the F1 was high and dose-dependent, and that among F2 larvae was even higher. The sex ratio of the F1 progeny was altered in favour of male, while that of the F2 was normal. 10 krad for P1 male was sufficient to inhibit hatching of the eggs produced by F1 adults.

The suitability of the East African goat and various types of hybrid goats to serve as hosts for tsetse was compared over an extended period. Although there was no significant difference between indigenous and hybrid goats when feeding up to 350 flies per host, about 94% more indigenous goats than hybrid goats became unsuitable as hosts and required a prolonged period of rest when the fly burden was increased to 450 flies per host. Of the hybrid types assessed, Toggenburg crosses were best suited as hosts even though they required more frequent rest periods than the other hybrid types.

A test with 100 nymphs of Hyalomma anatolicum anatolicum for evaluation of resistance of cattle to ticks was found to have a good potential for assessing the resistance status of cattle. Thus, 7% of nymphs engorged and moulted on a resistant host with average engorgement weight of 7.6 mg compared to 19 and 45% of engorged nymphs on two susceptible hosts with 15.8 and 13.6 mg average engorgement weights. Similarly, the number of detached fully engorged Rhipicephalus evertsi nymphs dropped from the resistant cows ranged between 14 and 57 compared with 118–124 from the two susceptible animals. The correlations between the three parameters; ranking cattle for resistance (natural tick burdens), the number of detached fully engorged R. evertsi nymphs, and the percentage survival of H. a. anatolicum nymphs after artificial infestation are discussed and found to be significant (r = +0.778; r = +0.886; r = +0.936). It is, therefore possible to assess the overall resistance status of hosts and cull the susceptible, if necessary.

The very tiny eggs of Daraba laisalis are often laid hidden between the body of egg fruits and its persistent sepals. After 4–5 days nearly all eggs hatch. The first instar caterpillar enters an egg fruit within 30 min of hatching, spends 8–15 days within it at a temperature of 24–32°C and r.h. 73–96%; it comes out a much bigger caterpillar to pupate in any convenient but hidden place near the egg fruit. The development of larva and pupa to adult and the morphology of the first and last instar larvae, the pupa and the adult are described. Behavioural peculiarities, longevity and predators of larvae are also mentioned.

Studies of the epidemiology of visceral leishmaniasis in the West Pokot focus have revealed that Sergentomyia bedfordi, S. antennatus and S. schwetzi are the most abundant sandfly species. The latter have been shown to feed mainly on lizards. Phlebotomus martini was encountered in termite hills in the ventilation shafts, and showed an even distribution among the termite hills throughout the district where kala-azar cases were detected. Investigations into the relationship between termite hills and the presence of kala-azar cases in various homes were carried out. All homes afflicted with kala-azar had a termite hill or hills within a 10-m radius. The period of time spent in own homestead by each kala-azar case was to establish if each kala-azar patient contracted the disease in the focus of investigation.

An analysis of the variation of fore-, mid- and hindgut contents in third- to sixth-instar nymphs of the African grasshopper, Zonocerus variegatus, freshly caught every hour in the field, and also left without food for 1, 6 and 12 hr, showed that gut motility and the movement of ingesta through the gut was maximal at 08.00–10.00, 13.00–14.00 and 16.00 hr. Movement of ingesta was very slow at night. A diurnal rhythm therefore governs gut emptying. Nymphs, confined in jars with leaf discs, fed from 07.00 to 19.00 hr over the temperature range 17–34°C. Most food was eaten after 13.00 hr when it is warmer. Field insects feed during the night as well. Midgut α- and β-glucosidase activity was detected at all times of testing (06.00, 12.00, 19.00 and 24.00 hr), but the levels of activity were lowest at 12.00 and 19.00 hr.

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.