The title of the paper in Volume 14, No. 3, page 389, by Pushpinder J. Rup and Parvinder K. Kalra should be Antennal Morphology in the Developing Polyphenics of Lipaphis erysimi (Kalt.) (Hemiptera: Aphididae)

Autoradiographic studies using 3H uridine in the salivary glands of three bugs, Lethocerus indicus, Laccotrephes rubra and Antilochus coqueberti show that the nuclei play an important role in contributing RNA. The labelled materials are seen to move into the lumen from the epithelia. RNA shows a tendency to accumulate in the lumen with ascending incubation periods. This behaviour in conjunction with its nucleolar genesis indicates its nature as rRNA. It is also believed that RNA might conjugate with some of the protein available in the lumen to produce RNP.

Studies were conducted in Niger in 1986 and 1987 on the population dynamics and parasitism of the millet stem borer, Coniesta (= Haimbachia) ignefusalis (Hampson) (Lepidoptera:Pyralidae), Sesamia calamistis Hampson, and the millet head caterpillar, Heliocheilus albipunctella de Joannis (Lepidoptera: Noctuidae). Planting dates were assessed for effects on population densities of C. ignefusalis and H. albipunctella. Population densities of C. ignefusalis were not reduced by adjusting millet planting dates, but were affected by millet growth stage. Platytelenomus sp. (Hymenoptera: Scelionidae) was the most common parasite of C. ignefusalis on millet. Parasitism of C. ignefusalis larvae and pupae was rare. Sesamia calamistis was a minor pest of millet in Niger, and was rarely parasitized. Population densities of H. albipunctella were reduced by delaying millet planting dates. Bracon hebetor (Hymenoptera: Braconidae) was the most common parasite of H. albipunctella.

Studies on cannibalism by Heliothis armigera (Hubn.) larvae on nuclear polyhedrosis virus (NPV)-infected larvae and feeding on virosed cadavers indicated that feeding was significantly higher on 4-day-old virosed cadavers followed by 1-day-old cadavers than on healthy or NPV-infected living larvae. The data revealed that cannibalism was significantly higher on NPV-infected (3 days post inoculation) larvae than either healthy larvae or those which had been just inoculated. However, the extent of feeding was higher on healthy larvae (cannibalistic feeding) than on cadavers. Significantly more number of larvae became infected by NPV when they fed on NPV-killed cadavers than on NPV-infected living larvae. Some of the larvae which had fed on either virosed cadavers or NPV-infected larvae survived. But, the disease was expressed in the pupal stage. Pupal mortality was significantly higher in larvae which fed on NPV-inoculated larvae (3 days post inoculation). The multiple choice test to find out the feeding preference of the larvae showed that the larvae had a greater preference to feed on virosed cadavers than either the healthy larvae or the host plant. The role of cannibalistic behaviour in the dissemination of the virus disease under field conditions is discussed.

A questionnaire survey was conducted to find out the information and knowledge of extension workers on thresholds of cotton bollworms, (Helicoverpa armigera and Diparopsis castanea). A sample of 30 extension officers was interviewed in Southern and Central provinces of Zambia. The results showed crucial deficiencies in extension worker's knowledge on thresholds of key pests and their implementation in cotton IPM. More than 60% extension officers were not aware of the basic information and knowledge such as thresholds of cotton bollworms, the recommended time to start scouting (weeks after germination of cotton) and the number of cotton plants to be examined for pest observance in each field. All extension officers indicated a desperate need for more field oriented practical training on thresholds. The recent increase in the incidence of aphids, Aphis gossypii as reported by 50% extension workers is obviously due to calendar sprays of synthetic pyrethroids and the lack of a suitable aphicide in current spray programme. Demonstrations on the practical aspects of thresholds deserve much more attention at college level and also during the in-service training. More co-operation in cotton IPM training for extension officers within Central and Southern Africa is suggested.

Heliothis armigera (Hubner) completed five generations in the laboratory, as well as in the field, in a year. The first generation was completed from the first week of December to the fourth week of February, the second generation from the second week of February to first week of April. The third generation from third week of August passing through the extreme summer, the fourth generation during monsoon period and the fifth last generation from the third week of September to the fourth week of November. The seasonal variation in generation time is largely due to extreme variations in ecological factors, temperature (10–45°C), photoperiod (10–14 hr), relative humidity (15–95%) and rainfall. These factors also affect the percentage of pupation, emergence and fecundity of the female moths. Males outnumbered the females in the first, second and fifth generation. The females lived longer than males in all generations.

Studies were conducted during the dry period February to May 1986 in River Shelliekha, Bahr El Arab fly belt, Sudan, to obtain baseline data on catch and age compositions, reproductive status and trypanosome infection rates of trapped and fly round samples of Glossina morsitans submorsitans. The objective was to assess the tsetse situation before the establishment of trypanosomiasis treatment stations at the northern limits of the fly belt. Trapped tsetse included significantly higher proportions of teneral and non-teneral females and a lower male:female ratio. Insemination rates were over 98% in both samples. In any one group, the frequency of pregnancy with egg predominated, followed by the second, first and lastly the third instar larva. There were significant differences between the two groups of females in the proportions of nullipars and pregnancy with any one of the larval instars. Abortion was the predominant reproductive abnormality and no relationship could be found between abortion rate and the sampling method, age or trypanosome infection rate of females. Age compositions were similar in the two samples, save for age categories 0 and 1 for females and two and four for males. Flies were infected with Trypanosoma vivax and T. congolense only, though T. brucei infections could also be diagnosed in livestock.

Life-fertility tables were described for Bracon hebetor Say (Hymenoptera: Braconidae) developing on the millet head caterpillar (MUC), Heliocheilus albipunclella de Joannis (Lepidoptera: Noctuidae). Mated B. hebetor females lived an average of 24.7 days, oviposited ca. 22 days, and produced 173.7 adult progeny with a 1:1 sex ratio. The estimated innate capacity of increase (ir) and net reproductive rate (R0) were 0.26 and 86.5, respectively. The mean generation time was 1 days.

Some aspects of flight behaviour in the triatomine bug Triatoma sordida were investigated. A strong link between flight initiation and nutritional status as expressed by weight: length ratio was shown. Flight activity was strongly nocturnal and unimodal, commencing with the onset of darkness. A capacity to lay eggs after flight initiation was noted.

Investigations were carried out to establish the phagostimulatory effects of cheaply available materials (bag sugar, sucrose, molasses) on Chilo partellus larvae. Sugar and analytical grade sucrose (1% w/v solutions) were the best phagostimulants tested. Molasses was the least effective but a 10% w/v solution induced a significant feeding response. These stimulants, in combination with a Bacillus thuringiensis treatment, were tested to determine their effects on increasing the efficacy of the pathogen against this pest species. Larval mortality levels were significantly higher in the presence of a feeding stimulant than when B. thuringiensis alone was administered; inclusion of such adjuvants in a B. thuringiensis preparation could significantly enhance the field efficacy of the pathogen against C. partellus.

The Senegalese grasshopper, Oedaleus senegalensis (Krauss, 1877) (Acrididae, Oedipodinae) survives the dry season under natural conditions as diapausing eggs. Females, reared under short photoperiod (10/24 hr), produced eggs which were mostly diapausing eggs, while those reared under long photoperiod (14/24 hr) laid essentially no diapausing ones (less than 3% of diapausing eggs). In addition, females submitted to a photoperiod of 10/24 hr, the percentage of diapausing eggs decreased with increasing female age.

Occurrence of mortality due to bacterial infection by a gram negative bacterium and the hymenopteran entomophagous parasite Apanteles glomeratus (L.) was observed in a natural population of Catopsilia crocale Cramer, a defoliator of the ornamental and medicinal plant Cassia alata. On regular field observation during the seasons 1980–1981 and 1981–1982, it was found that mortality due to these factors was mostly confined to the Final larval instar and the pupa of C. crocale. A direct correlation was obtained between population density of C. crocale and the number of larvae'pupae killed due to these factors. As the incidence of the hymenopteran parasite and bacteria fluctuate along with the C. crocale population, consideration of the foregoing factors as potential biological control agents for the pest population of C. crocale, is suggested.

The eggshells of Sergentomyia minuta, S. schwetzi and S. ingrami are studied by scanning (SEM) and transmission (TEM) electron microscopy. In all three species the surface sculpturing is characterized by a polygonal pattern due to intersecting ridges. Each ridge is formed by columns arranged in palisade and resting on a reticular basal layer. TEM shows that the columns represent the outer chorion and the basal layer the intermediated one. Under these layers an inner chorion and a vitelline envelope are present. The eggshell structures of the three species are compared with those of other Phlebotominae and their taxonomic value is discussed.

Studies were carried out to elucidate the parental (vertical) transmission of Nosema marucae Odindo and Jura, in infected females of Chilo partellus Swinhoe. Results indicated that only infected females of C. partellus could pass infection to the offspring. Infection also lowered both the total number of eggs laid per female and egg hatchability- Some adults which developed from the sublethally infected fifth instar larvae of C. partellus had deformed wings while some pharate adults failed to free themselves from the pupal cases. The significance of these deformities to the ecological survival of C. partellus is discussed.

The effect of mixed cropping cow pea with maize on general predators' abundance and their influence on population density of Megalurothrips sjostedti (Trybom) on cowpeas was investigated in the field and in exclusion cages. Populations of predatory ladybird beetles, Orius sp. and earwigs (Dermaptera) were not significantly influenced by mixed cropping. The density of spiders, however, was significantly higher in the cowpea sole crop than in the cowpea/maize mixture. The population density of M. sjostedti was significantly less in the cowpea/maize mixture than in cowpea sole crop, both inside cages, where predators were excluded, and outside. We concluded that this reduced population density was not the result of enhanced predators’ population in the mixture.

The growing recognition of problems associated with chemical pesticide use has led to increased attention on integrated pest management (IPM). This paper describes how Tunisian potato farmers have learned to manage an important field and postharvest insect pest, the potato tuber moth, Phthorimaea operculella (Zeller), and how interdisciplinary research on integrated pest management has contributed to this process. During the 1980s, new pest control technology and better farmer awareness led to changes in how farmers manage the potato tuber moth in their fields and stores. Farmers reduced insecticide treatments in potato fields and made more use of agronomic practices to avoid crop losses from the insect pest. New government regulations and agricultural extension efforts have caused farmers to discontinue use of environmentally harmful chemicals such as DDT. Research is continuing on biological insecticides that are not toxic to mammals and some farmer adoption of these products has occurred.

The distribution of 31 Glossina spp. and subspecies belonging to fusca, palpalis and morsitans groups is given for 38 African countries. The natural hosts of 17 tsetse species and subspecies from many areas within different regions of Africa are also given. These were collated from the results of both published and unpublished work, for the period 1953 to 1991 inclusive, comprising altogether 47, 697 bloodmeals. This review is aimed to provide current knowledge on the distribution as well as the natural hosts of tsetse.

Among the eight entomopathogenic fungi tested against the termite, Odontotermes obesus (Rambur), five fungal pathogens viz., Beauveria bassiana (Bals.) Yuil, Metarhizium anisopliae (Metsch.) Sorokin var. anisopliae, M. flavoviride Gams Rozsypal var. minus, Paecilomyces lilacinus (Thom) Samson and P. fumosoroseus (Wize) Brown & Smith, were pathogenic. Three other fungal pathogens viz. Verticillium lecanii Zimm, Paecilomyces farinosus (Holm, ex Gray) and Nomuraea rileyi (Farlow) were not pathogenic. B. bassiana was the most effective pathogen against termites, followed by M. anisopliae, M. flavoviride, P. lilacinus and P. fumosoroseus. Workers minor, of the three morphogenetic forms of O. obesus, were the most susceptible, followed by workers major and soldier caste. Bioassay on isolates of two most virulent termite pathogens, B. bassiana and M. anisopliae revealed that B. bassiana isolate Bapatla was the most effective fungal pathogen with the lowest LC50 (9.98 × 104 conidia/ml)

An additive effect was obtained after treatment of Spodoptera littoralis (Boisd.) larvae with a combination of Bacillus thuringiensis and nuclear polyhedrosis virus (NPVs). The NPVs was the more pathogenic followed by B. t., cytopathologically. Simultaneous application of B. t. and NPVs affected the midgut cells by causing a very specific appearance of cell hypertrophy with some deposits of B. t. crystals on the fourth day of infection as shown by scanning electron microscopy. Transmission electron microscopy showed that the vegetative cells and spores of B. t. entered the midgut epithelial cells followed by the virus. It is possible that the initial destruction caused by the B. t. toxin facilitated penetration and entry of the virus.

The occurrence of an orange body coloured mutant, governed by a single somatic recessive gene of the cotton stainer, Dysdercus koenigii is reported. Both the strains did not show any quantitative difference in growth, development and reproductive biology. Males of the orange mutant lacked any special preference for females of orange mutant. Inheritance of the orange mutant in mixed population showed its relative stability at about 21% from F2 to F8 generations. The utility of the orange mutant for studies on population genetics and dynamics of the cotton stainer is discussed.