Tomato plants in Nigeria were subjected to foliar sprays of Bacillus thuringiensis subsp. kurstaki (formulated as Dipel and Thuricide) and Baculovirus heliothis (Elcar), to which carbaryl, plus the adjuvants Tenac and Gustol were on occasion added, to test their effectiveness against Helicoverpa armigera (Hübner) and other lepidopterous larvae. H. armigera larvae were found susceptible to both pathogens. The 0·5 kg/ha and the 1·0 kg/ha applications of Bacillus thuringiensis gave good field control of the larvae, similar to that of carbaryl at 1·5 kg/ha. Bacillus and virus were compatible but not significantly more effective when combined than when applied separately. Combinations of bacillus and virus with carbaryl were also not significantly more effective than the pathogens applied separately. B. thuringiensis at 0·5 kg/ha applied with carbaryl at 0·5 kg/ha was as good as carbaryl at 1·5 kg/ha. Gustol and Tenac did not significantly increase the effectiveness of the pathogens.

The rate of oocyte development in Spodoptera exempta (Walker) was investigated in the laboratory and in the field in Kenya. Stages and rates of development were examined in relation to moth size and timing of mating and oviposition. The stage of oocyte development was established by measuring the widths of the second or third oocyte at the distal end of one ovariole. Data from moths of known age showed that oocytes were partially developed at eclosion and that a linear progression in development occurred up to 30 h after emergence, by which time the oocytes had reached approximately half their mature size. Oocyte development continued unbroken in some moths up to the time of oviposition on the second night after emergence, whilst the remainder arrested oocyte development for a varying number of days. Mating occurred after midnight, but only once the oocytes had reached a certain size, irrespective of whether development was continuous or arrested. In the latter case, this stage was reached immediately after development resumed. Oviposition usually occurred the night after mating, mainly around midnight and with a second peak towards dawn. The dawn peak derived from mature moths which mated and oviposited on the same night. It is suggested that moths arrest oocyte development to minimize wing loading during migration and that, since moths stay in arrested development for varying lengths of time (thought to be genetically regulated), dispersal is greatly enhanced.

The attack rate by the parasitoid Apanteles glomeratus (L.) on laboratory-reared larvae of Pieris rapae (L.) exposed for 3–4 day periods in a kale field in Massachusetts was greater when five larvae rather than two were placed on plants. The attack rate was greatest if host larvae were in the first instar when placed in the field, and little or no attack occurred when second- or third-instar larvae were exposed. The co-occurrence of unoccupied P. rapae larval feeding sites on plants where larvae were exposed reduced attack rates. Parasitism rates in trap-host larvae and in field-collected larvae (counting only cases in which the parasitoid was still in the egg stage) did not differ as estimators of recruitment to the population of parasitized hosts either in terms of total recruitment achieved per host generation or in the temporal pattern of the recruitment. In both simple and multiple linear regressions, the density of young P. rapae larvae (either parasitized or not) was the strongest correlate of parasitoid recruitment for the whole season, whereas average air temperature was the strongest correlate in the last month of observations (September).

Using several methods, claims that stem-borers, especially Scirpophaga incertulas (Walker), cause serious crop loss in deepwater rice were tested in Bangladesh. Insecticides were used to control different borer broods. Early season, pre-flood applications reduced infestation, but did not affect yield. One to three mid- to late-season applications of monocrotophos at 250 g a.i./ha significantly reduced infestation and/or whitehead numbers, with yield savings (7-10%) similar to those which earlier workers obtained by applying diazinon 20 times in a season. In each of six years, tiller populations peaked before flooding, then steadily declined until harvest, but stem-borer infestation varied, remaining low until late season in two of the years. In 1981, infestation lower than 24% pre-flood and 42% at harvest did not affect yield. In 1982, eighty-four correlation calculations showed no consistent significant effects of infestation (27-60%, C.V. 40%) on yield (25 000 stems were dissected). Anatomical studies of elongated stems revealed S. incertulas feeding neither causes significant structural damage nor seriously interrupts nutrient flow; also, the passage of a larva through a nodal septum is not detrimental. Irrespective of stem-borer attack, the submerged lower internodes commonly die, the fibrous remains anchor the upper stem, and nodal roots take over nutrient uptake. Studies of panicle-bearing stems (n = 838) showed that, even with 97% stem infestation, most yield loss results from infestation of the terminal internode and is manifested predominantly as whiteheads. In a specific study, 94% whiteheads (n = 205) were associated with terminal internode infestation, where larval feeding in the narrow stem had disrupted food conduction, so preventing grain-filling. The apparent tolerance of S. incertulas by deepwater rice varieties is consistent with their being a primitive group of cultivated rices.

A spray trial of a nuclear polyhedrosis virus (NPV) as an insecticide for Euproctis chrysorrhoea (L.) is described. The trial was carried out indoors in the spring on third-instar larvae emerging from overwintering nests onto small potted hawthorn trees (Crataegus sp.); the equipment used was the Turbair Fox Ultra Low Volume Sprayer. Dosages applied ranged from equivalents of 1 × 1011 to 1 × 1013 polyhedral inclusion bodies (PIB) per hectare. Infection was first detected in samples of live larvae after ten days and indicated rates of infection consistently lower than the final mortality attained. Larvae began to die of NPV infections 11 days after spraying, and mortality due to the virus ceased after ca 20 days; most larvae died in the fourth instar. Over the range of virus doses from 1 × 1011 to 5 ×10 12 PIB/ha mortality levels rose with dose, to a maximum of over 90%. Increasing the dosage to 1 × 1013 PIB/ha elicited no further increase in mortality. This preliminary trial suggests that the virus has considerable potential as a control agent, and field trials are, therefore, in progress.

In studies in Western Australia, temperatures in air and one- and two-litre pads of cattle dung set out weekly and ranging from one to 20 days old were measured hourly for 438 days over all seasons, producing 1437 day x dung-pad observations. Daily maximum temperatures (and hence thermal accumulation) in cattle dung pads could not be accurately predicted using meteorological data alone. An accurate predictor of daily maximum dung temperature, using multiple regression analysis, required measurement of the following factors: maximum air temperature, hours of sunshine, rainfall, a seasonal factor (the day number derived from a linear interpolation of day number from day 0 at the winter solstice to day 182 at the preceding and following summer solstices) and a dung-pad age-specific intercept term, giving an equation that explained a 91·4% of the variation in maximum dung temperature. Daily maximum temperature in two-litre dung pads was 0·6°C cooler than in one-litre pads. Daily minimum dung temperature equalled minimum air temperature, and daily minimum dung temperatures occurred at 05.00 h and maximum temperatures at 14.00 h for one-litre and 14.30 h for two-litre pads. Thus, thermal summation in a dung pad above any threshold temperature can be computed using a skewed sine curve fitted to daily minimum air temperature and the calculated maximum dung temperature.

Large colonies of holocyclic Rhopalosiphum padi (L.) were sampled in May-June in 1985 and 1986 from the principal host, Prunus padus, in various parts of Britain, mainly in the south-east. They were tested electrophoretically using nine enzymes representing 14 putative genetic loci. Only two loci (14%) were polymorphic (GOT, glutamate-oxaloacetate transaminase, and SORDH, sorbitol dehydrogenase), the remainder being monomorphic. Allele and genotype frequencies at each locus were generally similar both spatially and temporally, and genotype frequencies were close to Hardy-Weinberg expectations. The low level of genetic variability may reflect population bottlenecks which have purged most of the variation and which have been imposed by the distribution of P. padus, especially in the south of Britain where the tree is generally scarce. In addition, it is probable that adverse climatic conditions directly affect winter survival of anholocyclic populations of the aphid and thus also reduce variability. In the long term, such bottlenecks would tend to preclude the maintenance of effectively neutral enzyme variants that arise within populations. The similarity of allele and genotype frequencies may reflect the highly migratory behaviour of R. padi. Thus, in southern Britain, where P. padus is generally much rarer in comparison with the north of the country, R. padi inter-population gene flow is still sufficient to alleviate the influences of genetic drift and possible directional selection on the allelic variation that remains.

A dense layer of large insects in windborne, migratory flight was observed by radar in the Tilemsi Valley in Mali between about 23.00 and 02.00 h on 10–11 October 1978. The volume density, height of flight, area density, displacement speed and direction, orientation and migration rate were determined for the overflying insects. Light-trap catches and radar signatures provided strong evidence that the pest grasshopper Diabolocatantops axillaris (Thunberg) contributed to the overflying layer. Other species contributing probably included Oedaleus senegalensis (Krauss) and possibly Ochrilidia spp. For D. axillaris, the migration can be regarded as a search for overwintering sites by adults in reproductive diapause, and thus is an example of C. G. Johnson's Class III migration. Estimated trajectories placed the probable source areas of the overflying grasshoppers in the Gourma, about 150 km west-south-west of the radar site. Migration direction was approximately downwind, but the grasshoppers showed a degree of common orientation towards the east-south-east, which added a southwards component to their displacement. At 02.30 h on the same night, a very dense line-concentration associated with a wind-shift moved across the radar site, and insects still in flight probably became entrained in this wind convergence zone and added to the line-concentration. Other evidence of long-distance, windborne migration in D. axillaris was adduced from records of captures on ships at sea, mainly off the West African coast. The consequences of downwind displacement and concentration for grasshopper ecology and pest management are discussed. The migration behaviour of D. axillaris and other grasshopper species probably reduces migration losses by the efficient location of new habitats and forms an essential part of life-history strategies for survival in a sahelian environment.

Groups of gravid females of Lucilia cuprina (Wiedemann) in a 1-m3 cage flew upwind in response to sheep placed upwind of the cage. No downwind flight or other response was observed to sheep placed downwind of the fly cage. Flystruck sheep stimulated the greatest accumulation of flies on the upwind cage wall (46% of the caged flies), followed by sound wet sheep (29%) and sound dry sheep (19%). All sheep tested caused significantly more flies to accumulate on the upwind wall than did controls consisting of either no bait or a man placed upwind (14%). Struck sheep elicited significant upwind movement of flies at distances of up to 20 m; sound, dry sheep did so only up to 10 m. It was concluded that L. cuprina is able to orient from a distance in response to volatile sheep kairomones; kairomones from dry sheep are augmented by wetting or the presence of cutaneous myiasis, as indicated by an enhanced fly response. The experiments performed did not exclude a role for visual or thermal cues in blowfly orientation to sheep.

The attractiveness of cattle urine to Glossina morsitans morsitans Westwood and G. pallidipes Austen was shown to be entirely attributable to the phenolic components which it contains. Four of the eight naturally occurring phenol derivatives (3- and 4-methylphenol, 3-ethylphenol and 3-n-propylphenol) were electroantennographically active, induced upwind flight in wind-tunnel bioassays and increased trap catches in field tests in Zimbabwe. One of the minor components, 2-methoxyphenol, had little antennographic activity but induced upwind flight in the wind-tunnel and appeared to be repellent in field tests.

In Zimbabwe, catches of Glossina morsitans morsitans Westwood and G. pallidipes Austen in traps baited with acetone and 1-octen-3-ol were increased by the addition of the synthetic mixture of eight phenols found in cattle urine to a level equal to or greater than those with natural urine. The addition of natural urine to the synthetic mixture did not increase catches further, indicating that the phenols account for essentially all the attractiveness of cattle urine. 4-Methylphenol and 3-n-propylphenol were shown to be the naturally-occurring components essential for attractiveness, and 2-methoxyphenol was found to reduce attractiveness. 4-Methylphenol alone was slightly attractive to both species, but only for males, increasing catches by approximately 30%. Catches of both species were increased by approximately 50% by 3-n-propylphenol. The addition of 4-methylphenol increased catches of G. pallidipes by up to a further four times, but catches of G. m. morsitans were decreased. Of 14 other phenols tested, phenol, 3-methylphenol and 4-ethylphenol increased the attractiveness of 3-n-propylphenol to G. pallidipes without decreasing the attractiveness to G. m. morsitans; (E)- and (Z)-3-(1-propenyl)phenol, potential contaminants in 3-n- propylphenol, did not reduce the attractiveness of mixtures of 3-n-propylphenol and 4-methylphenol, and the E and, to a lesser extent, the Z isomer could substitute for 3-n-pro-pylphenol in these mixtures. Mixtures of phenols which increased the attractiveness of traps to tsetse showed similar effects with targets but at a slightly reduced level.

The landing preferences of fed males of Glossina morsitans morsitans Westwood and Stomoxys calcitrans (L.) were measured under constant conditions in a two-choice situation. Pairs of black-and-white landing targets were presented on the grey walls of an arena ca 60 cm in diameter. In a simple choice of blackness vs whiteness, G. m. morsitans showed a ninefold greater preference for black; S. calcitrans displayed no preference. G. m. morsitans landed twice as frequently on a 15×30-cm vertical black stripe as on a horizontal one, but S. calcitrans preferred the horizontal one. Comparisons between a vertical stripe (or a horizontal one) and similar stripes sloping at various angles indicated that at about 50° G. m. morsitans distinguished the sloping stripe from the vertical (or the horizontal), but did not well distinguish slopes closer to the vertical (or horizontal). Tests with multiple vertical stripe patterns indicated that G. m. morsitans did not significantly distinguish between a single 15-cm stripe and two- or three-striped targets of the same total black area, but landed significantly less frequently on targets of four or five stripes, implying an angular, behavioural visual ‘resolution' of roughly 17°; S. calcitrans responded similarly. Both species showed a marked preference for landing near the edge of the black on all targets, with G. m. morsitans strongly biassed to the black side of an interface.

Gyranusoidea tebygi sp. n., an encyrtid parasitoid of Rastrococcus on mango in India, is described and compared with related species. The parasitoid is to be introduced into West Africa in an attempt to control the mealybug, which is a serious pest of mango and citrus in some West African countries.

Chironomid midges have been known to include parthenogenetic species for over a century. One of these species, Paratanytarsus grimmii (Schneider), cited under several different names here shown to be junior synonyms, has attained some notoriety as a pest. Its occurrence as a supposedly paedogenetic (actually pharate adult parthenogenetic) inhabitant of water distribution systems is discussed and related to its more usual occurrence in a variety of small water bodies including aquaria. New synonymy is proposed and a lectotype designated.

A quantitative analysis of the foraging behaviour of Acromyrmex octospinosus (Reich) from three nests on 27 yam varieties of nine species was undertaken in Guadeloupe using a video-microcomputer device. In ants with no previous experience of the variety, foraging inhibition appeared only after at least a whole day of contact with resistant yam leaves. There was a negative correlation between leaf saponin content of the yam species and foraging intensity; however, the main yam sapogenin, the steroid diosgenin, had no effect on foraging behaviour, and tomatin, a steroid-alkaloidal saponin, induced only long-term deterioration of the fungus garden when incorporated in the nest. The saponins tested are thus not detected by the ants and are therefore unable to initiate the strong and rapid foraging inhibition observed with resistant yams.

Major potential sources of variation in the feeding of Nilaparvata lugens (Stål) which are not host-dependant are those related to time, i.e. the age of the insect, the length of time the insect is in association with the plant and the time of day. These parameters were investigated with a susceptible, a moderately resistant and a resistant rice variety using honeydew clocks for the collection of honeydew excretion data. It is concluded that there are non-circadian patterns of honeydew excretion which are related to the degree of resistance of the variety and that such feeding and excretion patterns can be used to characterize the relationship between insect populations and rice varieties.

Rhopalosiphum maidis (Fitch) collected on barley in the northern hemisphere usually has a ten-chromosome karyotype, whereas samples from maize, sorghum and Johnson grass (Sorghum halepense) from all parts of the world commonly have 2n = 8. Samples with other karyotypes (2n = 9, 2n = 11 and 2n = 8 heterozygous for an interchange between the X chromosomes) occur less frequently on these and other species of Gramineae. Multivariate morphometric analysis, principally by the method of canonical variates, indicated that the ten-chromosome form may be regarded as a single clone of R. maidis recognizable by its karyotype and host-plant relationships, although not completely separable by morphology alone from all other clones of this permanently parthenogenetic species complex.