Cotesia flavipes Cameron, a gregarious larval endoparasitoid native to the Indo-Australian region, was imported from Pakistan and released in Kenya in 1993 for management of the exotic stemborer, Chilo partellus (Swinhoe). Recent reports confirmed the successful establishment of the parasitoid in three locations in Kenya and in northern Tanzania. Functional response studies on this parasitoid and an indigenous congener, Cotesia sesamiae (Cameron), indicated that C. flavipes had a higher searching ability and attacked more larvae when Chilo partellus was the host. When a native stemborer, Sesamia calamistis Hampson, was the host, there was no significant difference between numbers attacked by both parasitoids. Numerical response studies showed that Cotesia flavipes produced more total progeny and female progeny per female parasitoid on Chilo partellus than did Cotesia sesamiae. No significant difference in progeny production was detected between the two parasitoids on S. calamistis. Functional and numerical responses tested in the laboratory gave the same ranking of the two parasitoids on the two hosts as in the field. This study suggests that Cotesia flavipes is a more efficient parasitoid and it is anticipated that it will contribute to the control of both exotic and native stemborers in Kenya.

Male Glossina morsitans morsitans Westwood and Glossina pallidipes Austen caught in artificial refuges in Zimbabwe had ca. six times as much haematin and up to 32% more fat than flies from odour-baited traps, but haematin-specific fat levels did not differ significantly between methods. G. pallidipes estimated to have fed < 9 h prior to sampling contained ca. 3.3 mg fat - only 10% less than peak levels. A differential equation model for blood-meal metabolism was developed which described well the changes in fat levels of laboratory G. m. morsitans and the relationship between fat and log haematin in field data. The model predicts a mean feeding interval (T) of 54 – 65 h and mean fat levels of ca. 2.8 mg for G. pallidipes at feeding. When haematin frequency data were analysed as suggested in the literature, estimates of feeding rates and intervals, and of the non-feeding phase, varied with sampling method. Published estimates of activity levels related to feeding suggest a model where feeding rates increase approximately linearly during the trophic cycle. For T = 58 h the model gives good predictions of mean fat levels and variances in both species, with starvation rates < 1% / day. Models with long non-feeding phases predict fat levels up to 40% lower than observed and with smaller variances. For constant feeding rates, fat levels were well predicted for T = 54 h, but predicted death rates (> 5% / day due to starvation alone) were impossibly high. It is suggested that a proportion of tsetse flies with high fat levels feed on mobile hosts early in the trophic cycle and that this effect is more marked for G. m. morsitans than for G. pallidipes. Over-estimates of T result from the failure to consider these tsetse flies and not to errors in the assumed time scale, nor failure to catch high-fat tsetse flies which visit stationary traps.

The reproductive condition and mating status of female Helicoverpa armigera (Hübner), H. punctigera (Wallengren) and the mating status of the armywormMythimna convecta (Walker), trapped in tower-mounted light traps were studied over a four and a half year period, from November 1985 to December 1989. The traps were mounted on towers (40 and 50 m high) in two geographically distinct sites, one located at Point Lookout and the other at Mt Dowe both in north-eastern New South Wales, Australia. At the Point Lookout site, 132 females of H. armigera and 366 of H. punctigera were examined and of those, 88.7% and 89.9% were unmated and immature, respectively. Most of the remaining females of both species were mature and mated. Of the matedH. armigerafemales, 78.6% carried only a single spermatophore, the remainder having either two or three spermatophores. Most of the matedH. punctigerafemales (97.1%) carried only a single spermatophore and the remainder had no more than two. Females ofM. convectawere predominantly (97.1%) unmated. At the Mt Dowe siteH. punctigeraadults were predominant and all 44 females of this species examined were unmated and non-gravid. Pre-reproductive flight byHelicoverpaspp. andM. convectais considered as an important component of the life-history strategies of these insects. Flexibility in the timing and spacing of reproductive effort is seen as enabling colonization of heterogeneous environments.

The duration of flight by Nilaparvata lugens (Stål) of tropical origin from field and laboratory populations was studied. Field insects (from the third generation on rice) flew longer and more readily than laboratorybred insects. The longest recorded flight, of 10·75 h, was by a female from the field. Laboratory-reared insects performed poorly even after only one generation in the laboratory. Flights that were started in the morning lasted longer than those started in the afternoon. Lift production varied between individuals and during a continuous flight. Individuals flying for over 150 min tended to produce more lift for a longer proportion of the flight than those flying for less than 10 min. The pattern of lift production appeared to be similar in successive flights, except in those following very long flights when the insect appeared to be exhausted. There was no tendency for the first flight to be the longest. Up to 28% loss of body weight was recorded (in a flight lasting 512 min) during flight. The results indicate that individuals from tropical field populations of N. lugens have the capacity for long range migration.

The course of embryonic development of S. gregaria under controlled conditions of temperature and humidity is described, with special attention to the water requirements of the developing egg. The development of the egg is interrupted if contact water is lacking and is resumed when the egg is moistened. This occurs at the stage of late anatrepsis, which is the stage at which the embryo of some other locusts and grasshoppers undergoes diapause.

The current global increase in prevalence of vector borne diseases, as well as an expansion of tropical infections to more temperate zones, justifies further studies on vector populations. Urban areas may favour viral transmission to humans through close contacts between the vectors and the vertebrate hosts, and also affecting mosquito populations by offering larval habitat, refuges and adequate microclimates to survive the winter. This work analyses the spatial distribution of potential vector mosquitoes in relation to landscape characteristics in an urban environment in a temperate climate region. Mosquitoes were trapped monthly from October 2005 to March 2006 in 25 sites within Córdoba city and suburbs with miniature light traps+CO2. Nine species were collected, and the most abundant were Culex quinquefasciatus (37.1%), C. apicinus (26.6%) and Aedes aegypti (13.9%). Species that may be involved in SLEv transmission were recorded throughout the sampling. C. quinquefasciatus was detected in 92% of the sites; however, only two sites showed consistently larger collections. The site of highest C. quinquefasciatus abundance was located within an area of high Saint Louis Encefalitis virus prevalence and risk of infection, further supporting this species involvement as a vector. Significant correlations were detected between land cover characteristics and abundance of C. apicinus, C. interfor and C. maxi that were consistent with previous knowledge about their larval habitat and domestic preferences, which may be useful for targeting vector control operations.

The accumulation and transmission of tomato spotted wilt virus (TSWV) was examined in second instar larvae and adults of two thrips genera, Frankliniella and Thrips. The species tested were F. occidentalis (Pergande), F. intonsa (Trybom), T. tabaciLindeman, T. setosus Moulton, T. palmi Karny and T. hawaiiensis (Morgan). In a standard petunia leaf disc assay, the efficiencies of TSWV transmission by two species of Frankliniella were higher than those of any Thrips species in the adult stage. A triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) showed that large amounts of the TSWV-nucleocapsid (N) protein were present in the ELISA-positive larvae of each species, with the exception of T. palmi. The ELISA titre of and the proportion of virus-infected individuals of the two Frankliniella species increased or did not significantly change from the larval to the adult stages, whereas those of the four Thrips species decreased significantly. These results show that the specificity of virus transmission by adult thrips is probably affected by the amount of viral N protein accumulation in the adults and that the accumulation pattern from the larval to the adult stages is in between the two genera tested in the present study.

Laboratory colonies of Monomorium pharaonis (L.) were given access only to food containing the juvenile hormone analogue isopropyl-11-methoxy-3, 7, 11-trimethyl-dodeca-2, 4-dienoate (Altosid). In contrast to control colonies all the brood died in 4–8 weeks and queens ceased to lay eggs at about this time. Comparison of ovaries dissected from treated and untreated queens showed the former to be atrophied and without developing oocytes. In treated colonies the worker caste became extinct between 9 and 20 weeks after treatment commenced but queens remained alive for more than 20 weeks. Treatments were lethal with exposure periods of one week only. Juvenile hormone analogues show real potential for the control of M. pharaonis.

A laboratory study of aspects of parasitoid host acceptance, suitability and physiological regulation in natural and novel host species was carried out to investigate the degree of variability encountered with different hosts and to determine the value of such observations in host range determination. The parasitoid Microctonus aethiopoides Loan was exposed to a natural host, Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) and three novel hosts, the New Zealand native Nicaeana cervinaBroun, the introduced weed biological control agent Rhinocyllus conicus (Froehlich), and a congeneric pest species, Sitona lepidus Gyllenhal (all Coleoptera: Curculionidae). Per cent parasitism of these species was 54%, 43%, 39% and 0%, respectively. The results indicated that for both S. discoideus and R. conicus more males than females were parasitized (69% cf. 45%, and 49% cf. 32% respectively) but host size was not a significant factor. Overall, superparasitism was recorded in about 29% of parasitized weevils and there was evidence that host discrimination to avoid superparasitism occurred in the natural host. Conversely, superparasitism occurred more frequently than would be expected in N. cervina (42%) coupled with higher survival of larvae in superparasitized hosts in this species. The frequency distribution of attack of R. conicus by M. aethiopoides was not different from random. Parasitoid development was more rapid in the natural host, S. discoideus, and parasitoid size was positively correlated with host size. There was a strong positive relationship between parasitoid larval survival and the presence of teratocytes in all hosts. Host fecundity and fertility were reduced by parasitism for most species, and in some cases, by exposure to parasitoids in the absence of detectable parasitism. It was concluded that laboratory observations can provide useful information on the compatibility between host and parasitoid which can complement traditional host range tests to predict field host range.

Two experiments were conducted at Galana Ranch, Kenya, which examined, under natural conditions, the relationships between the number of tsetse flies (Glossina pallidipes Austen) attracted to cattle, the rate at which the cattle made defensive movements, and the feeding success of the tsetse. The most frequent defensive movements were skin ripples and tail swishes, while leg kicks were of intermediate frequency, and head and ear movements were infrequent. In one experiment, the rate of skin ripples, but no other type of defensive movement, was significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was significantly (P < 0.004) correlated with the rate of leg kicks, more weakly with the rate of head movements (P < 0.07), and uncorrelated with the rates of other types of defensive movement. In the second experiment, the rates of skin ripples, tail swishes and leg kicks were significantly correlated with the number of tsetse attracted to the cattle. The proportion of tsetse that engorged was again significantly correlated to the rate of leg kicks (P < 0.03), more weakly to the rate of head movements (P < 0.04), and unrelated to the rates of other types of defensive movement. In neither experiment was there a significant relationship between the number of tsetse attracted to the cattle and the proportion that engorged, suggesting that any density-dependent feeding success was too weak to be detected. In experiment 1, the relative fat content of the male G. pallidipes that fed decreased as the rate of leg kicks increased, suggesting that when hosts are more active the sub-sample of tsetse that feed, out of those that approach, is both smaller and hungrier. There was no detectable effect of host defensive behaviour on the bloodmeal size of male G. pallidipes.

Schistocerca piceifrons (Wlk.) is the swarming locust of tropical America. It has until recently been confused with closely related species and has usually been misidentified as S. paranensis (Burm.). The biological information that can definitely be attributed to this species is reviewed and is supplemented with some original observations. The invasion area of the locust includes Mexico, Central America, Colombia, Venezuela, Guyana, Ecuador and Peru. Permanent populations are known from the Yuc´tan Peninsula, northern Honduras, the Pacific coast of Central America and the highlands of Peru. There are two subspecies, S. piceifrons piceifrons, known from Mexico and Central America, and S. piceifrons peruviana Lynch Arrib., from Peru. S. piceifrons exhibits phase polymorphism in nymphal colouration and adult morphometrics. The femur length/maximum head width (F/C) ratio is most effective in separating the phases. There are two generations a year. Immature adults of the second generation survive the dry season. Its habitat is subclimax mosaic communities in areas where the natural vegetation is dry tropical woodland. Plagues are believed to have originated when swarms formed in the permanent breeding areas. Records of susceptible crops and natural enemies are given, and the behaviour of hopper bands is described.

Females of Anopheles minimus Theobald at a site in northern Thailand that were caught on man or domestic bovids and were released showed a significant tendency to return to the type of host upon which they were first caught (P = 0·03). From a total of 3526 individuals marked and released, 51 were recaptured. A simple explanation is that the taxon is in fact a mixture of two or more morphologically cryptic species, a suggestion already indicated by previous studies.

The economic importance of Capnodis in Palestine is discussed; the various species and their hosts are enumerated.

The egg is described and its shell chemically analysed. It was found that potassium, calcium and magnesium are present as cations and chloride and carbonate as anions.

The effects of relative humidity upon the egg are discussed. It is pointed out that the egg is resistant to a low percentage, but succumbs to a high percentage of relative humidity. The rôle of the egg shell in this matter is important.

The effects of the temperature upon the eggs are discussed. Their development at various temperatures is calculated, and the Blunck formula applied. The mortality of the egg at high and low temperatures is shown in tables.

Pygostolus falcatus (Nees), an endoparasitic Braconid of the subfamily Blacinae, was reared from Sitona lineatus (L.), S. hispidulus (F.) and S. humeralis Steph. of Swedish origin. The life-history and immature stages of P. falcatus were studied in the laboratory at 74°F. and in field cages preparatory to its liberation in Canada as a control agent of the sweetclover weevil, S. cylindricollis Fhs.

The immature stages develop in the haemocoele of the weevil. After deposition, the egg increases in volume to a maximum of 335 times. At eclosion, the cells of the trophamnion dissociate and increase in volume in relation to the growth of the larva. Supernumerary larvae are eliminated soon after eclosion, and one larva only develops in a host weevil. At 74°F., the final-instar larva emerges from the host weevil 15–16 days after deposition of the egg. Development of many first-instar larvae in a wide range of Sitona species was arrested by diapause. Five larval instars are described and illustrated. Oviposition is prevented in weevils in the summer of their development and eliminated in overwintered weevils by the parasite egg and first-instar larva. The weevil dies within hours of emergence of the parasite larva.

Reproduction is parthenogenetic and thely tokous. The maximum number of eggs laid by a female was 46; the number of eggs laid per day per female varied from 0 to 11. Oviposition takes place both in light and in complete darkness and a preference among species of Sitona was not evident. The maximum number of weevils parasitised by a female in a field cage was 39; the number parasitised per day varied from 0 to 8.

The species overwinters as a first-instar larva in weevils which became adult in the previous summer. There were two discrete parasite generations in 1958 in Swedish weevils, both of which developed in early and mid-summer within overwintered weevils. The maximum rate of parasitism of S. lineatus by larvae of the mid-summer parasite generation in 1958 was 73·3 per cent.

The value of P. falcatus as a control agent of Sitona populations is limited by low parasitism of the new weevil generation of the current year and diapause of the first-instar larva.

Living specimens of Megarhinus brevipalpis were transported from southern Natal to Johannesburg to establish an insectary-bred colony. The natural habitat of these predatory mosquitos consisted of small isolated patches of sub-tropical forest, in which the rainfall is 40–50 ins. (102–127 cm.) with a mean winter temperature of 64°F. (17·7°C.) and an annual range of 27°–33°F. (15°–18°C). The breeding places were leaf axils of Strelitzia nicolai (a plant resembling a wild banana), small rot holes in trees and larger ones in Strelitzia stumps. The larvae were collected from leaf axils with an apparatus consisting of a rubber bulb to which were attached lengths of glass and rubber tubing.

The insectary was a room 9 ft.×8 ft. 6 ins. and 9 ft. high which was kept at tropical heat and humidity. Mating of the adults was observed, copulation being effected while at rest or in flight. Oviposition was usually accomplished in flight but also while at rest on the surface of the water. In the summer time two females, which were tested, laid about 85 eggs each during the month following emergence from the pupa, six or seven days elapsing after emergence before the first oviposition. In the middle of the winter, oviposition (with later generations) became very irregular in spite of the temperature and humidity remaining constant. The adults, which were comparable to those of the natural habitat, were fed on sugar solution, honey and fruit juice. One bred out as a gynandromorph.

When given an abundant supply of larvae of laboratory bred Aëdes aegypti, the life-cycle of M. brevipalpis was normally : egg (incubation), less than two days ; larva, 11–20 days (average 14·5 days) ; pupa, five days. This does not include a small number of exceptional cases in which the life as a fully grown larva was abnormally prolonged (in one case nearly four months) for reasons which are not absolutely clear. The larvae killed from 100 to 200 or more Aëdes larvae during the normal larval life, but many of these were not eaten when the brevipalpis were in the late fourth instar. By a special technique they were also induced to eat dead tissues including minced pork brawn, minced maggots and minced flies. Except for the latter these were not satisfactory foods although there was slow development.

Fourth-instar larvae were kept out of water for three to four weeks (without food), in a damp atmosphere, and afterwards when fed most of them developed normally, but pupation was sometimes suspended for a considerable time. They have been sent by post (out of water) in tubes with damp cotton wool and filter paper.

The egg differed from that of other Megarhinus species in having a crown of projections at one end with a cup-like structure in the centre. The exochorion had roughly hexagonal cells but without numerous tubercles as in other species.

First-instar larvae remained in the egg-shell after hatching when the eggs-were out of water but on a damp surface and in a saturated atmosphere. They survived like this for up to six days or about the same time as the larvae survived in tap water if there was no food. When liberated in water the head of the first-instar larva was comparatively small with the mouth parts folded in. Within two hours of liberation in water the head enlarged considerably and the mouth parts came into position ; the larva was then ready to catch its Culicine prey. When in water containing dead leaves, these larvae survived from a few days to over four weeks and some grew to the third instar without any Culicine food.

Cannibalism was investigated. Fourth-instar larvae did not attack each other readily ; they devoured smaller larvae of their own species and small to medium size larvae resorted to cannibalism, particularly in the absence of Culicine prey. There was evidence that fourth-instar Aëdes aegypti occasionally ate first-instar Megarhinus.

The discussion traces attempts which have been made in certain Pacific islands, notably Hawaii and Fiji, to use Megarhines for biological control of disease-carrying mosquitos. M. brevipalpis has a shorter life-cycle than the species introduced into these islands and the conclusion reached is that laboratory breeding, to enable large numbers to be released in certain areas, would be a suitable adjunct to a programme of general control, in this part of the world. Airmail consignments of larvae are being sent to Hawaii with the object of starting a laboratory colony there.

Culex quinquefasciatus Say from Peliyagoda, Sri Lanka, has elevated esterases A2 and B2. In vitro insecticide metabolism studies on the temephos-selected Sri Lankan Cutex quinquefasciatus strain, Pel RR, showed that fenitrothion was hydrolysed more rapidly than malathion. A significantly larger amount of fenitrothion was metabolized in Pel RR compared to the insecticide susceptible Pel SS strain, but the amount of malathion metabolized in the two strains was not significantly different. There was more esterase hydrolysis of fenitrothion than oxidase or glutathione S-transferase metabolism in Pel RR, which suggests that the elevated esterases in this strain have both metabolic and sequestering functions and that the relative importance of the two roles depends on the insecticide used. Genetic crosses of the temephos resistant and susceptible strains, showed that both resistance and elevated esterase activity were inherited as semi-dominant multi-genic characters. Hydrolysis of 2-naphthyl acetate was highest in the Pel RR strain, lowest in the Pel SS and intermediate in the F1 cross of the two strains. A minor maternal effect on resistance occurred with backcrosses involving resistant (F1) females, which gave consistently and significantly lower mortalities than those involving resistant (F1) males.

The development, survival, and reproduction of the black citrus aphid Toxoptera aurantii (Boyer de Fonscolombe) were evaluated at ten constant temperatures (4, 7, 10, 15, 20, 25, 28, 30, 32 and 35°C). Development was limited at 4 and 35°C. Between 7 and 32°C, developmental periods of immature stages varied from 44.2 days at 7°C to 5.3 days at 28°C. Overall immature development required 129.9 degree-days above 3.8°C. The upper temperature thresholds of 32.3, 28.6, 29.3, 27.2, and 28.6°C were determined from a non-linear biophysical model for the development of instars 1–4 and overall immature stages, respectively. Immature survivorship varied from 82.1 to 97.7% within the temperature range of 10–30°C. However, immature survivorship was reduced to 26.3%at 7°C and 33.1% at 32°C. Mean adult longevity was the longest (44.2 days) at 15°C and the shortest (6.2 days) at 32°C. The predicted upper temperature limit for adult survivorship was at 32.3°C. Total nymph production increased from 16.3 nymphs per female at 10°C to 58.7 nymphs per female at 20°C, declining to 6.1 nymphs per female at 32°C. The estimation of lower and upper temperature limits for reproduction was at 8.2 and 32.5°C, respectively. The population reared at 28°C had the highest intrinsic rate of increase (0.394), the shortest population doubling time (1.8 days), and shortest mean generation time (9.5 days) compared with the populations reared at six other temperatures. The population reared at 20°C had the highest net reproductive rate (54.6). The theoretical lower and upper temperature limits for population development, survival and reproduction were estimated at 9.4 and 30.4°C, respectively. The biology of T. aurantiiwas also compared with three other citrus aphid species.

Cytotaxonomic analysis of the polytene chromosomes from larvae of the Simulium damnosum Theobald complex from the island of Bioko in Equatorial Guinea is reported, and a new endemic cytoform is described. Chromosomally this cytoform is close to both S. squamosum (Enderlein) and S. yahense Vajime & Dunbar, but is not identical to either. However, it is morphologically and enzymatically identical to S. yahense. The Bioko form was also found to differ from other cytoforms of the S. damnosum complex in West Africa in the copy number or RFLP pattern of several different repetitive DNA sequences. It is clear that the Bioko form is genetically distinct from other populations of the S. damnosum complex, and whilst it is closest to S. yahense, it shows features that suggest a high degree of geographical and genetic isolation. Such isolation is an important consideration in the assessment of the potential for onchocerciasis vector eradication on Bioko.

Histological examination of the eyes of Glossina morsitans Westw. and G. austeni Newst. showed that visual acuity, as calculated from ommatidial size and interommatidial angle, varies in different zones and planes of the eye, being greatest in the forward-facing region. A study of optomotor responses to revolving black-and-white striped patterns indicated that the eyes could perceive both rapid and very slight movement: responses showed a unimodal distribution with frequency of ommatidial stimulation ranging from one flash/25 s to around 80 flashes/s, with an optimum response at 5 flashes/s. Movement perception was also enhanced by summation of ommatidia simultaneously stimulated, provided the stimulated ommatidia were not contiguous. Strong optomotor response was shown to the movement of black stripes so narrow as to cause merely a 7% reduction in the amount of light entering an ommatidium: from this it was inferred that the eye's contrast sensitivity is well developed. Visual acuity determinations from optomotor responses showed no species or sex differences, and the values corresponded closely with those obtained from anatomical measurements. Of the properties of selected figures examined for attractiveness to orienting flies, linearity of form and brightness contrast with background illumination were deduced to be the most important aspects.

Sitophilus oryzae (L.) is a pest of stored cereals and, because most populations are unable to survive on yellow split-pea and other legumes, admixture of legume with cereal has been suggested as a control method. However, some geographical strains have been found able to feed and breed on yellow split-pea. The ability is heritable and known to be controlled in one strain by a single recessive, autosomal gene. The inheritance pattern of the ability was investigated in three different geographical strains, two of which could feed and breed on yellow split-pea and one which could not. The genetic mechanism controlling the character in these strains was not a simple recessive allele, but differed between the two pea-breeding strains and was co-dominant with the inability to feed on yellow split-pea inthe non-pea-breeding strain. The results indicate there is considerable between-strain genetic variability for the character, which may render cereal-legume mixture of little value as a control method against S. oryzae.