The midge, Contarinia sorghicola Coquillett, is a major pest of grain sorghum in many areas of Asia, Africa, Australia, Europe and America. Literature documenting the status of research on the biology, behaviour, and field and cage screening techniques is reviewed. Numerous germplasm entries have been evaluated and many resistant sources are identified from various midge screening programmes. A high degree of resistance was found in nine working groups viz., Caudatum, Durra, Caudatum/Nigricans-Zerazera, Caudatum/Kafir (Hegari), Nigricans, Caffrorum-Darso, Durra-Nigricans, Durra-Nandyal and Caudatum-Bicolor. The identified resistant sources and the midge resistant varieties released from the breeding programmes are listed. Studies on the mechanisms of resistance showed predominance of antixenosis for oviposition over adult attraction and variable degrees of antibiosis. The morphological characters and biochemical factors associated with resistance have been explored. Short and compact glumes which remain closed during anthesis conferred resistance. The tannin content in the ripening sorghum grain is related to resistance against the larva. The inheritance of resistance showed quantitative nature. The open and closed glume character expression indicated its dominance and recessiveness, respectively. Short glume character can be used as an useful genetic marker. Pedigree and modified pedigree breeding systems were suggested to transfer high level of midge resistance into agronomically acceptable types for selection and hybridization.

The location of olfactory and gustatory sense organs in the larvae of the American bollworm, Heliothis armigera, have been studied using the scanning and transmission electron microscopy. The olfactory chemoreceptors of the larvae are located on the antennae, mostly on the top of the second antennal segment in the form of two trichoid sensilla, two basiconic sensilla, two styloconic sensilla, campaniform sensilla and a uniporous peg sensillum. The third antennal segment bears one basiconic sensillum and two styloconic sensilla. The gustatory sense organs are located on the mouthparts including the labrum, mandibles, hypopharynx, maxillary palps and labium. Trichoid sensilla have been located on the labrum. Epipharyngeal setae as well as long short spines are located in the epipharyngeal membrane. The basal segment of the maxillary palp bears three trichoid sensilla and one campaniform sensilla. The maxillary palp also bears four styloconic sensilla on the distal portion of the lateral protuberance and one styloconic sensillum at the apex of the medial protuberance. Close to the bases of the protuberances, there are three basiconic sensilla and one campaniform sensillum. The third apical segment of the maxillary palp carries three campaniform sensilla on its lateral side, while on its top, eight small basiconic sensilla are distributed.

Viruses have been identified in a large number of insect species and many have been shown to have a regulating effect on natural populations of insects. Increasing dissatisfaction with the use of chemical pesticides has resulted in a search for biological control agents such as viruses. A number of insect viruses, primarily the occluded viruses (baculoviruses and cytoplasmic polyhedrosis viruses) have been used effectively to control pest species of insects. This review describes the major groups of viruses which infect insects and the areas of research that are being pursued.

The conventional theology regarding the role of science in the social and economic development of the Third World is that its crucial function must be the transfer of technology from the science-based industrialized countries to the developing regions of the world. Indeed, ever since 1963, when the world took part in the “United Nations Conference for the Application of Science and Technology to Development” in Geneva, Switzerland, national planners in the Third World and economic planners attached to the donor community, have been consumed by the concept of transfer of technology as a short-cut to science-driven socio-economic development in the Third World. The 1979 United Nations Conference on Science and Technology for Development, on the same theme held in Vienna, Austria, reinforced this concept, and rather confirmed the policy of focussing human and financial resources on the technology facets of science rather than on the fundamental research aspects.

Dacus oleae (Gmelin) is a major pest of the olive tree Olea europea causing early fruit drop, ‘sting’ damage to table olives and substantial decreases in the quantity and quality of oil. This review describes the control strategies being developed and in current use—biological, trapping methods, sterile insect release, chemical insecticides, growth regulators and integrated control. Present problems and the implications of the controlling regimes on the disturbance of the agroecosystem are presented. Emphasis is given to newer methods which should be characterized by their specificity and effectivity.

Integrated pest management (IPM) is nowadays considered the most appropriate approach to pest control. The introduction of IPM in developing countries is however not easy. Experience shows that it is a long-term process. Some experience of IPM programmes are briefly discussed (cotton in Latin America; rice in South East Asia and basic food crops in the Sahel). The attention of tropical entomology should not be focused on IPM only, but also be directed at problems not directly related to IPM. These include the need for better pesticide management, the avoidance of further spread of pests to previously infested area and the control of grasshopper outbreaks in Africa.

The recently developed “International Code of Conduct on the Distribution and Use of Pesticides” which was unanimously adopted by FAO Member Countries in 1985, can be an important instrument for better pesticide management. To make this code work is a challenge. The control of introduced pests absorbs resources which otherwise could have been used for the control of indigenous pests. Therefore quarantine measures should be strengthened to prevent such spread. Strengthening of Plant Protection Services represents another challenge as these services play a key role in pest control in general and also in implementing IPM. Training in biological control has to be strengthened with emphasis on practical methods which effectively lead to better field pest control. Biological control units have to be set up in countries where they do not exist. There is no fixed level of IPM which should be reached. IPM strategies should fit local conditions and be promoted in conjunction with improved agricultural practices. Priorities for intervention have to be set when developing IPM programmes.

Floral characteristics related to pollination were studied in four species of Theobroma and one species of Herrania (Sterculiaceae) in Costa Rica. Anthesis was complete in T. cacao, T. simiarum, T. speciosum, and T. mammosum at 0615 hr following an extended period of floral development throughout the night. Flowers of both T. cacao and Herrania cuatrecusana were fully open by dawn and pollen sacs dehisced throughout the morning hours. Stigma and style receptivity, assessed by hydrogen peroxide tests, were high throughout the morning and early afternoon in T. cacao. Bagged flowers resulted in no fruit-set. When petal ligules were experimentally removed there was no change in rates of flower abortion or total numbers of aborted flowers, tentatively suggesting that these structures play little or no role in attracting pollinators. Both Theobroma and Herrania flowers possess ultraviolet light reflectance'absorbance patterns which may play a role in pollinator attraction. Uptake of neutral red stain in T. cacao and T. simiarum showed scattered glandular activity on petals and sepals, perhaps indicating location of nectaries or other secretory organs. Conspicuous glandular trichomes on the ovary, on the lower third of the style, and in a conspicuous “basal ring” between petals and sepals (most pronounced and colorful in species other than T. cacao) may be sources of both floral attractant and reward.

Differences in floral biology among Theobroma and Herrania species suggest divergence in pollination strategies. The data presented are discussed in terms of plant-pollinator specializations in the New World tropics.

Glossina pallidipes was recorded from two widely separated areas in southern Sudan, far from any previously known localities: west of Torit, Eastern Equatoria Province and around Yambio, Western Equatoria Province. These records are discussed in relation to the local habitat and associated tsetse species; and it is suggested that G. pallidipes may be becoming more common and widespread in the region.

A preliminary taxonomic review of cassava green spider mites, Mononychellus spp., from their South American topotype and from several African countries indicates that the dorsal central body setae is not a reliable and stable diagnostic character as it was found to widely vary. The taxonomie implication of this is discussed.

The tropics abound with insect diversity; yet we hardly know about a tenth of them. Destruction of natural habitats due to deforestation, monoculture and urbanization results in their extermination or change of habits, often with devastating results. If the insects are to be properly managed for the benefit of mankind, an inventory of them should be taken before they are destroyed and their habits and habitats studied. A team of well trained taxonomists is required. Taxonomie centres are to be developed where taxonomists can be trained and insect collections can be housed and studied. Taxonomie manpower and resources should be developed in various countries of the tropics so that the rich and abundant insect diversity is studied and finally utilized for the benefit of mankind.

Investigations on storage insects infesting stored groundnuts was carried out in farms, markets, stores and out-door storage sites in order to find out the source of infestation. Farm samples were found to be free from infestation. Freshly harvested groundnuts that were just stacked into pyramids were also free from infestation. However, groundnuts stacked into pyramids at central storage areas of Kano and Gusau were highly infested following a year of storage. Groundnuts from stores and markets were moderately infested. The most abundant and widely distributed insect pests were Tribolium castaneum (Herbst) and Oryzaephilus mercator (Fauvel). Ephestia cautella (Wlk.) constituted less than 1% of insect pests found on the groundnuts, but Plodia interpunctella (Herbst) was absent in out-door pyramid storage.

Groundnuts kept in in-door storage had high moisture content, while nuts from farm and open air pyramid storage had low moisture content. Lipid, peroxide and free fatty acid (F.F.A) values from groundnuts were directly related to the levels of infestation.

Three populations of C. mbila originating from the rain forest (Ibadan), southern part of sudan savanna (Kadawa, Kano) and the Jos Plateau, and C. triangula population from Ibadan (Moor Plantation) were compared in relation to their ability to acquire and transmit maize streak virus (MSV). Acquisition and transmission efficiency increased with time of access feeding. Joint regression analysis showed that the populations did not differ significantly from each other in transmission efficiency of the virus. Nymphs and adults of some populations acquired MSV in 30 sec and adults transmitted the virus during the 2-hr inoculation access. Efficiency of virus transmission generally increased with acquisition or inoculation time.

The minimum latent period of maize streak virus in the various Cicadulina populations was 14–18 hr and the medium latent period (LP 50) was 16–20hr. Some individuals in all populations retain the virus throughout their lives.

Since the various Cicadulina populations were largely similar in their ability to acquire and transmit the virus into healthy maize, other factors which might be implicated in the epidemiology of maize streak disease are discussed.

The study showed three generations of the olive fruit fly from June to November 1984. Eggs were first detected in the Shami variety in early June. There were three peaks of eggs found in almost all varieties in late June, late August and late October. Highest number of larvae was found in Santa in July, and Ascolano and Kheli in August. There were no significant differences in the number of larvae per 100 infested fruits between all varieties during the first generation except Nabali. Pupae inside the fruits first appeared in Shami in July. The number of pupae inside the fruits was high in all varieties in August. Holes made by larvae falling to the soil for pupation were recorded in early August in all varieties, except Nabali where they appeared in late August and early September. During the second generation the highest number of larvae was found in Ascolano, Santa and Rase'e varieties. The recorded parasites were Opius concolor, Eupolmus urozonus, Tetrastichus sp., Trichostereresis glabra, and Lasioglassum sp. The most abundant parasites were O. concolor and Tetrastichus sp.

Motile zoospores, the only infective stage of Pythium species, attached, encysted and infected 100% second instar larvae of Aedes aegypti, Aedes africanus, Aedes simpsoni, and Anopheles gambiae. Motile zoospores variably attached and infected Culex spp. and Eretmopodites but did not attack field collected Toxorhynchites sp. We observed mycelial development within the exposed larvae after exposure indicating that mortality was due to the fungus. The fungus infected 75 ± 10% (SD) second instar larvae of Aedes aegypti, under aseptically reared conditions. It infected 65 ± 12.8% (SD) second instar larvae of Culex quinquefasciatus in aseptic conditions in the laboratory. All field collected larvae were heavily infested with vorticella but after treatment with 5% sodium hypochlorite, control mortalities ranged from 0 to 8.6% (mean = 4.3%).

The fungus was most infective between 20–27.5°C; at 30°C many zoospores were attached to the cuticle but did not infect. Mortality rates were as low as 51.5% at 30°C, with no infection at all at 35°C. pH range from 6–8 was optimum for infection, but pH above 8 inhibited infection. Infection level of 100% was obtained in aseptically reared larvae at higher densities of 1600 larvae of second instar larvae of Aedes aegypti and 97% infection for 1600 second instar larvae of C. quinquefasciatus when exposed to fungal infection. Phosphate, borate and acetate buffers inhibited zoospore production.

Seasonal occurrence of the beetle, Dirphya nigricornis Olivier, was monitored in the field for 3 years. Two coffee varieties, French mission and SL34 with capped and uncapped canopies respectively, were used to estimate the egg niches in two coffee estates at Ruiru, Kenya. The total egg niches in the short and long rainy seasons represented low infestation (1.56–8.21%), which was nearly stable throughout the study period, 1982–1984. In some cases, however, seasonal significant (P = 0.05) variety-to-variety differences existed between egg niches at each studied site. The distribution of the egg niches of D. nigricornis occurred on branches between the 1st and 21st internodes of primary and tertiary shoots of either variety. Egg niches were negatively correlated (r = −0.44 to r = −0.99, 19d.f.) to internode position in all five categories of the shoots examined. The beetle therefore concentrates infestation and does not place its progeny randomly on coffee shoots.

Floral fragrance oils related to pollination were studied in three species of Theobroma and one Herrania species (Sterculiaceae) in Costa Rica. This study was prompted by field observations that floral odours and floral visitors are markedly different between Theobroma and Herrania, as well as between species of Theobroma.

Floral fragrance in cultivated T. cacao consisted of 78 components, primarily saturated and unsaturated hydrocarbons, with 1-pentadecene the major constituent followed by n−pentadecane. The distribution of 1-pentadecene was similar at 0900 hr (43.6%), 1130 hr (52.5%) and 2000 hr (51.1%) sampling times but only 1.2% at 1600 hr. The ratio of 1-pentadecene to n−pentadecane in the 1600 hr sample, approximately 1:6, contrasted with a 3:1 ratio at 0900 and 1130 and a 6:1 ratio at 2000 hr. The greatest concentration of volatiles was found in the 1130 hr sample, with 0900 and 2000 hr concentrations being essentially equal and intermediate between the high (1130 hr) and the low (1600 hr).

Of the 58 compounds detected in T. mammosum steam distillate at 0815 hr, an array of linalool oxides accounted for 12.5% of the oil followed by isoeugenol (8.9%). Saturated hydrocarbons were also present but, unlike T. cacao, n-tricosane was the major hydrocarbon (12.2%). The major constituents of T. mammosum oil clearly distinguish this species from T. cacao.

A markedly different profile of major floral volatiles was found in T. simiarum: major constituents included the monoterpenoids citral, geraniol, nerol, and citronellol. Unlike the oily, hydrocarbon fragrance of T. cacao and T. mammosum, T. simiarum floral fragrance is citrus-like both in the field and laboratory. Our fragrance studies suggest considerable evolutionary divergence within Theobroma.

The floral fragrance of H. cuatrecasana contained volatiles characteristic of dipteran-pollinated plant species. Unusual volatiles found in Herrania fragrance included iridomyrmecin, guaiol, and other azulenic derivatives. No such monoterpenoids and bicyclic sesquiterpenoids (with the exception of longifolene, 0.1%, in T. simiarum) were found in Theobroma. The profiles of floral fragrance chemotaxonomically support the exclusion of Herrania spp. from the genus Theobroma.

This Symposium was held on 1 September 1986 to assess available resources and current requirements for biosystematic research, identification and other services in support of entomological work in the tropics, especially in Africa, India and S.E. Asia. Particular attention was given to biosystematic services for agriculture and to the need for long-term financial support to maintain and develop reference collections; to train and employ taxonomists; to provide identification services and to undertake biosystematic research at local, national, regional and international levels.