The vertical and horizontal distribution of Tribolium castaneum (Herbst) in a rice warehouse was studied using flight traps hung around selected stacks of bagged rice. Traps hung at 4 m or higher from the floor caught more T. castaneum than other insect species in the warehouse. At 6 m height, the traps caught mainly this species and were easy to maintain. The horizontal distribution pattern of T. castaneum sampled at 6 m was not homogeneous. The factors influencing distribution are discussed.

Sperm-transfer in Culicoides melleus (Coq.) is achieved by means of an intermediary spermatophore. The form of the spermatophore, only the second to be observed in a species of Culicoides, is described and illustrated. Though generally similar to others reported in Diptera, the spermatophore of C. melleus is distinguished by the presence of a long neck attached to the main capsule. Formation of the spermatophore occurs after sexual union has been achieved, and throughout mating the capsule remains held in the male apparatus. The distinguishing functional feature is that the entire length of the neck lies within the common duct of the spermathecae. The presence of an appendage of the spermatophore inside the spermathecal duct is a hitherto unknown phenomenon in Nematocera.

Over a period of six years, the presence or absence of 23 species of arboreal insects (13 Homoptera, 1 Heteroptera, 9 ants (Hymenoptera: Formicidae)) was recorded on each of 866 young Amazon and Amazon hybrid cocoa trees at the Cocoa Research Institute, Tafo, Ghana. The general form of the time-series, derived from the proportion of trees occupied by each species, is described. Analysis of 18 of these series, taken either singly or jointly, was carried out using analysis of variance and principal components analysis and the degree of spatial association between 16 of the species was also investigated. For the latter, the number of joint occurrences of pairs of species was compared with the expected number by means of a chi squared test. An index of association was derived from the proportion of occasions on which the difference was significant. For all but four species, there were highly significant differences between annual means in the analysis of variance and, in many, the overall annual trend was downward with time. For those species where significant differences were not shown between years, trends were often apparent on individual plots but were negated because of inconsistencies between plots in the direction of the trend. In the joint analysis of all 18 species by principal components, the first component accounted for approximately 33% of the total variance and could be identified as representing to a large extent the long-term upward or downward trends shown up by the analysis of variance. The second principal component, accounting for a further 13% of total variance, was interpreted as being a further manifestation of the long-term trend, representing a tendency for deviation from the trend line shown up by the first component to become less with time and to approach the trend line in a damped oscillation. This is thought to be partly caused by a drought at the start of the experiment which affected certain species adversely. The third principal component accounted for 11% of total variance and the scores followed an irregular annual cycle which was related to relative humidity. The scores on this axis were high during dry periods of the year and low during wet periods. In the analysis of variance it was found that 13 species showed significant differences in spatial distribution between seasons and, for most, there was evidence for an annual cycle. There was also some evidence of correlation between the seasonal cycles of some insects with seasonal rainfall level or morning or afternoon relative humidity. These same species are important in contributing to the third principal component scores. Spatial association analysis showed eight species to be strongly associated. These fell into three groups with positive associations between members of the same group and negative association between members of other groups. Each group featured an ant-homopteran association, Crematogaster spp. with Planococcoides njalensis (Laing) in group 1, Oecophylla longinoda (Latreille) with Stictococcus spp. in group 2, and Camponotus spp. and Polyrhachis laboriosa F. Smith with Planococcus citri (Risso) and Toxoptera aurantii Boyer de Fonscolombe in group 3. Three other coccids were loosely linked to these groups through particular members, Waxiella sp. nr zonatus (Newstead) to group 1 through Planococcoides njalensis and to group 2 through Camponotus spp. and Phenacoccus hargreavesi (Laing) and Steatococcus spp. to group 2 through Planococcus citri. Changes taking place with time in the relative abundance of members of these groups could be discerned in the trajectories of the first two principal components. The spatial re-arrangements taking place with time of the territories of the major ant species are followed in some detail, and the effect of these changes on Homoptera is discussed.

In a survey of adult ticks infesting livestock in Ethiopia, 33 species and subspecies were identified. The distribution and abundance of each are discussed in relation to ecology (altitude, climate and vegetation). Amblyomma variegatum (F.) is the most widespread and abundant tick parasitising cattle. A. cohaerens Dön. is common on cattle in wetter western habitats but is replaced by A. gemma Dön. in drier eastern areas. A. lepidum Dön. occupies intermediate habitats. The distribution of Boophilus decoloratus (Koch) is similar to that of A. variegatum. Hyalomma truncatum Koch and H. marginatum rufipes Koch are both common except in extremely arid and humid zones. H. anatolicum anatolicum Koch, H. anatolicum excavatum Koch, H. dromedarii Koch, H. erythraeum Tonelli-Rondelli, and H. impeltatum Schulze & Schlottke are usually associated with camels in semi-arid areas of eastern Ethiopia. Rhipicephalus evertsi evertsi Neum., R. sanguineus (Latr.) group and R. simus Koch do not display marked ecological preferences. East of the Rift Valley in semi-arid areas below 2000 m, R. pulchellus (Gerst.) is abundant on cattle and camels. R. longicoxatus Neum. and R. pravus Dön. inhabit drier localities, but R. lunulatus Neum. occurs only in wetter western areas. Species taken infrequently were A. nuttalli Dön., A. sparsum Neum., B. annulatus (Say), Haemaphysalis aciculifer Warb., H. leachii (Aud.), H. parmata Neum., H. spinulosa Neum., Hyalomma marginatum marginatum Koch, H. marginatum turanicum Pom., H. punt Hoogst., Kaiser & Pedersen, Ornithodoros savignyi (Aud.), R. longus Neum., R. muhsamae Morel & Vassiliades, and R. senegalensis Koch. The seasonal dynamics of the common species and observations on their relationships to tick-borne diseases of man and domestic animals are discussed.

The predatory mirid Macrolophus praeclarus is widely distributed throughout the Americas, and is reported to prey upon several horticultural pest species. However, little is known about its biology, thermal requirements, crop odour preferences, phytophagy, and capability to induce defensive responses in plants. When five temperatures studied (20, 25, 30, 33 and 35°C) were tested and Ephestia kuehniella was used as prey, the developmental time from egg to adult on tomato, was longest at 20°C (56.3 d) and shortest at 33°C (22.7 d). The ability of nymphs to develop to adults decreased as the temperature increased, with the highest number of nymphs reaching the adult stage at 20°C (78.0%) and lowest at 35°C (0%). The lower and upper developmental thresholds were estimated at 11.2° and 35.3°C, respectively. The maximum developmental rate occurred at 31.7°C and the thermal constant was 454.0 ± 8.1 degree days. The highest predation rate of E. kuehniella eggs was obtained at 30°C. In Y-tube olfactory choice tests, M. praeclarus selected tomato, sweet pepper and eggplant odours more frequently than no plant control treatment. Macrolophus praeclarus feeding did not damage tomato plants compared to another zoophytophagous mirid, Nesidiocoris tenuis, which caused necrotic rings. The phytophagy of M. praeclarus induced defensive responses in tomato plants through the upregulation of the jasmonic acid metabolic pathway. The implications of the findings for using M. praeclarus in tomato biological control programmes in the Americas are discussed.

Understanding the biological parameters of some triatomine subspecies of Meccus phyllosomus (Burmeister) is a crucial first step in estimating the epidemiological importance of this group. Biological parameters related to egg eclosion, egg-to-adult development time, number of blood meals to moult, percentage of females at the end of the cycle, number of laid eggs, and the accumulative mortality for each instar of three M. phyllosomus subspecies [Meccus phyllosomus pallidipennis (Stål), Meccus phyllosomus longipennis (Usinger), and Meccus phyllosomus picturatus (Usinger)] as well as their laboratory hybrids were evaluated and compared. No significant differences (P > 0.05) were recorded among the experimental hybrids (M. p. longipennis × M. p. pallidipennis, M. p. longipennis × M. p. picturatus, M. p. pallidipennis × M. p. picturatus) and reciprocal cohorts. In five of the six studied parameters (egg eclosion, egg-to-adult development time, number of blood meals to moult, number of laid eggs and accumulative mortality), with the exception of the non-significant percentage of females obtained among all the studied cohorts, at least one of the parental cohorts in each set of crosses exhibited better fitness results than by those of their hybrid descendants. The lack of hybrid fitness in our study indicates the maintenance of reproductive isolation of parental genotypes. Moreover, the results lead us to propose that an incipient speciation process by distance is currently developing among the three studied subspecies, increasing the differences between them that modify the transmission efficiency of Trypanosoma cruzi to human beings in Mexico.

The curculionid Cyrtobagous salviniae Calder & Sands and the pyralid Samea multiplicalis Guenée were released in north-eastern Australia for the biological control of the floating fern Salvinia molesta. C. salviniae destroyed large areas of weed and was successful at coastal and elevated sites. At equilibrium, there was less than 1 adult/20 plants and only a few, very small plants at each site. The rate at which the weed was controlled varied with mat density. The moth did not reduce plant growth permanently at any site and did not interfere with the performance of the weevil.

The Mormon cricket (MC), Anabrus simplex Haldeman, 1852 (Orthoptera: Tettigoniidae), has a long and negative history with agriculture in Utah and other western states of the USA. Most A. simplex populations migrate in large groups, and their feeding can cause significant damage to forage plants and cultivated crops. Chemical pesticides are often applied, but some settings (e.g. habitats of threatened and endangered species) call for non-chemical control measures. Studies in Africa, South America, and Australia have assessed certain isolates of Metarhizium acridum as very promising pathogens for Orthoptera: Acrididae (locust) biocontrol. In the current study, two isolates of Metarhizium robertsii, one isolate of Metarhizium brunneum, one isolate of Metarhizium guizhouense, and three isolates of M. acridum were tested for infectivity to MC nymphs and adults of either sex. Based on the speed of mortality, M. robertsii (ARSEF 23 and ARSEF 2575) and M. brunneum (ARSEF 7711) were the most virulent to instars 2 to 5 MC nymphs. M. guizhouense (ARSEF 7847) from Arizona was intermediate and the M. acridum isolates (ARSEF 324, 3341, and 3609) were the slowest killers. ARSEF 2575 was also the most virulent to instar 6 and 7 nymphs and adults of MC. All of the isolates at the conidial concentration of 1 × 107 conidia ml−1 induced approximately 100% mortality by 6 days post application of fungal conidia. In conclusion, isolates ARSEF 23, ARSEF 2575, and ARSEF 7711 acted most rapidly to kill MC under laboratory conditions. The M. acridum isolates, however, have much higher tolerance to heat and UV-B radiation, which may be critical to their successful use in field application.

The cigarette beetle Lasioderma serricorne through transportation affects the infestation of stored tobacco. Using amplified fragment length polymorphism (AFLP), DNA polymorphisms were assessed in 16 populations of L. serricorne collected from 15 countries. The dendrograms constructed from profile distance matrices revealed well-supported colony clusters. There was no clear clustering as a function of the geographic origin of the samples. The results suggest extensive insect dispersal among geographical regions due to movement of infested commodities worldwide. This first AFLP population study of a stored-product insect demonstrates the potential of AFLP for distinguishing L. serricorne populations.

In order to see if aeration causes grain beetles to become peripherally distributed in bulks of grain, the positions of adults were recorded 7–10 days after they had been placed in the middle of vertical columns of wheat 1200 mm long and 80 mm in diameter. The columns were held at 10 or 25°C, and a downward current of air was passed through half of them. At 10°C, there were more adults of Oryzaephilus surinamensis (L.) at the ends and fewer at the centre of aerated than unaerated tubes when a high airflow was used, and at 25°C, a similar difference occurred when aeration caused cooling, dampening or drying of the grain. Dampening at 10°C and drying at 25°C caused there to be fewer adults of Sitophilus granarius (L.) at the ends and more at the centre of aerated than unaerated tubes. However, vibration at 10°C encouraged the dispersion of weevils. Rhyzopertha dominica (F.) scarcely moved at 10 or 25°C under either aerated or unaerated conditions.

All the species described in this paper were obtained at Peradeniya, Ceylon, by Mr. A. Rutherford, the Government Entomologist, and were forwarded by him to the Imperial Bureau of Entomology for identification. In every case the types are deposited in the British Museum.

Mealybug populations (Pseudococcus njalensis Laing) originally present in piles of slash infected with the virus of swollen shoot of cacao are usually small. It is suggested that many of the insects leave the trees at an early stage in the development of infection.

Slash piles offer conditions which induce mealybugs to remain within them. The piling of infected slash retards the rate of wilting of the cut wood and consequently retards the rate of migration of the mealybug population. The construction of piles protects the mealybugs from direct insolation and rainfall and leads to the persistence of the population on the cut wood. The colonies which survive the longest are those in the lower part of the heaps where death and desiccation of the material is most delayed.

Mealybugs continue to live and to reproduce within heaps of slash for as long as nine weeks or more. Reproduction of the mealybugs is stimulated as the tissues of the felled trees become wilted and the resulting first-instar nymphs contribute numerous participants to such migration as does occur. There is evidence from laboratory experiments that these insects are not potential vectors.

The concentrating of mealybugs in slash piles produces no increase in the population of Coccinellid or Cecidomyiid larvae within the piles.

Mealybugs are capable of walking quite rapidly for long distances over smooth surfaces. They become incapable of movement when starved for a few days and the majority die within a week. A soil surface seriously impedes the progress of mealybugs which leave the slash heaps and this effect is more marked with the nymphal stages. Even on clean-weeded soil the rate of travel is slow and few. if any, insects can travel over appreciable distances in the period during which the virus may persist within them. Results of preliminary experiments were confirmed by the use of insects labelled with radioactive phosphorus.

Some of the ants, which become associated with slash piles and which remain in attendance of the residual mealybug population, carry mealybugs, but the number of insects transported in this way is of little practical significance.

The establishment of migrating mealybugs on seedlings and mature cacao is poor even in the presence of their attendant ants.

All these factors make the possibility of infecting healthy trees from infected slash extremely remote. There is accordingly no reason to believe that the efficiency of “ cutting out ” is seriously reduced by the movement of vectors from the infected trees which are cut out.

Without the co-operation of farmers in supporting the removal of contact trees no further recommendations can be advanced to improve the present method of control of swollen shoot.

Microbracon kirkpatricki, sp. n.

♂♀. Pale reddish testaceous with the 1st and 2nd tergites often almost stramineous ; antennae of a darker red ; extreme apex of tarsi black ; ovipositor sheaths dark brown to black ; the male often with the 2nd–5th tergites discally brownish ; ocelli black, the ocellar area sometimes darkened ; legs, particularly the hind legs, often stramineous or nearly so ; stigma and wing veins pale reddish, except that in the forewing the 1st abscissa of the anal vein and the basal half of the 1st abscissa of the medial vein are virtually colourless, and that the costal vein is brownish, and that the stigma in the males is brownish.

♀. Integument noticeably coriaceous throughout, except the appendages. Head broadly rounded behind, 1·75 times as broad as long ; ocelli on a more or less distinct tubercle, not close together, the posterior ones only somewhat nearer to one another than to the eye ; flagellum with 25–29 joints, the majority of specimens with 27–29 joints ; apical joint of antennae wth a short apical style ; head impunctate and narrowly coriaceous. Thorax impunctate, with mesonotum, scutellum, and propodeon, more broadly coriaceous than the head ; mesopleurae more broadly coriaceous again ; the lines of the notauli only faintly indicated, but noticeable, chiefly on account of the enclosed median area which is raised somewhat and which, tapering to a point, reaches almost to the scutellar depression ; scutellar depression apparently sometimes weakly crenulate and sometimes plain ; propodeon completely plain except for a median, very weak, longitudinal excavation extending about half the length of the propodeon, when it becomes a fairly well marked longitudinal carina which extends to apex, where it joins the transverse apical ridge.

Tinea pellionella (L.), commonly known as the Case-bearing Clothes Moth or Fur Moth, is of world-wide distribution and is of considerable economic importance. It has been recorded on a variety of substances, particularly those of a keratinous nature. In India, it has been found as an important pest of woollen textiles. Its life-history and habits have been systematically investigated at different levels of temperature and humidity.

The incubation period is 4 to 5, 5, 6 to 7 and 6 to 7 days at 21·5, 25, 30 and 32·5°C., respectively. Temperatures higher than 32·5°C. have been found lethal to eggs. Humidity has no effect on the incubation period. Percentage viability of eggs is greater at lower than at higher temperatures.

Both temperature and humidity have been found to influence the larval development and the number of larval instars. Irrespective of temperature, higher humidities favour shorter larval development and the shortest larval period is at 25°C. and 90 per cent. R.H.

Woollen materials impregnated with yeast are more suited for the larval development than those not so treated. Larvae do not exhibit colour preference. Woollen fabrics dyed with Cloth fast orange G 4 per cent, manufactured by “ Ciba ”, however, inhibit the growth of freshly hatched larvae.

The behaviour of the larvae to direct sunlight has been studied. The rôle of (a) diffused light alternated with darkness, (b) darkness, (c) temperature and (d) humidity on the extent of damage caused by the larvae has been investigated. Under the conditions of the experiments, the amount of damage in continuous darkness was significantly greater than in alternating light and darkness, and that at 90 per cent. R.H. significantly greater than at 30 per cent., but there was no significant difference in the amount of damage at 27·5° and 32·5°C., respectively, and 90 per cent. R.H.

The mode of pupation has been described. The pupal period has been studied and found.to occupy 18 ± 0·4, 10·3 ± 0·16 and 10·3 ± 0·33 days at 21·5, 25 and 30°C. and 90 per cent. R.H., respectively. Humidity has no effect on this period.

The effect of temperature and humidity on (a) the preoviposition, oviposition and postoviposition periods and (b) number of eggs laid by a female has been studied. The life-span of the male and female, the relationship between the weight of the female at emergence and fecundity (which was highly significant) on the one hand and length of life (which was not significant) on the other has also been investigated. Sex ratio between females and males has been found to be 2·6:1. Three to four generations in a year have been recorded at 26 ± 8·0°C. and 82 ± 10 per cent. R.H. when the larvae are fed on woollen fabrics impregnated with yeast.

Investigations have been made on the influence of environmental conditions on the contact toxicity to adult mosquitos (Anopheles stephensi List.) of two kinds of insecticidal deposits of importance in sprayed houses, superficial deposits from wettable powders and insecticides sorbed on dried soils.

Increasing the relative humidity from 43 to 80 per cent, during the contact period had no effect on the toxicity of wettable-powder deposits on plywood of dieldrin, Sevin and O-methyl O-(2,4,5-trichlorophenyl) ethylphosphoramidothioate. On the other hand, the availability of DDT, dieldrin and 3-isopropylphenyl N-methylearbamate sorbed on dried soils increased considerably as atmospheric humidity increased. The logarithm of the median lethal exposure time was linearly related to atmospheric humidity, and decreased by a factor of 2·8, 2·2 and 2·1 for the carbamate, dieldrin and DDT, respectively, for each 10 per cent, increase in relative humidity. There was also a linear relationship between the logarithm of the water uptake of a given soil and humidity.

Temperature affected the action of insecticides during both the contact period and the post-treatment period. Median lethal doses of dieldrin, Sevin and the phosphoramidothioate decreased, and that of DDT increased, as the post-treatment temperature increased from 20 to 30°C. These effects of the post-treatment temperature were also found when treatment was by exposure to residues. When these effects were eliminated it was found that the contact toxicity of superficial deposits on plywood and of insecticides sorbed on dried soils increased as the temperature during the exposure period increased. A simple relationship between median lethal time and exposure temperature was indicated.

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short-cut turfgrass in Eastern North America. Wide spread insecticide resistance warrants the development of alternative management strategies for this pest. ABW damage typically occurs in areas with a high percentage of annual bluegrass, Poa annua L., the preferred ABW host. Damage to bentgrasses, Agrostis spp., is much rarer and usually less severe. To aid the implementation of host plant resistance as an alternative ABW management strategy we investigated the tolerance of three bentgrass species to ABW feeding. Responses of P. annua, creeping bentgrass, Agrostis stolonifera L., colonial bentgrass, Agrostis capillaris L., and velvet bentgrass, Agrostis canina L., to adult and larval feeding were compared in greenhouse experiments. Grass responses were measured as visual damage, dry weight of the grass stems and leaves, color, density and overall grass quality. To determine possible mechanisms of grass tolerance constitutive fiber and silicon content were also determined. The three bentgrass species tolerated 2–3 times higher numbers of ABW adults and larvae than P. annua before displaying any significant quality decrease. Creeping bentgrass had the lowest damage ratings. ABW infestation caused higher plant yield reduction in P. annua (up to 42%) than in bentgrasses. Observed differences among the grass species in fiber and silicon content in the plant tissue are unlikely to play a role in the resistance of bentgrasses to ABW. Our findings clearly show that A. stolonifera is the best grass species for the implementation of host plant resistance in ABW management.

The ambrosia-beetles of Ceylon comprise a number of genera of Scolytidae and Platypodidae. It is proposed only to deal with beetles belonging to the former family which are included in the subfamily Cryphalinae, adding a few notes on the Platypodids.

Cross-mating occurred under laboratory conditions between Diparopsis castanea Hmps. and D. watersi (Roths.), although this subsequently resulted in only a slight egg hatch. Assays involving the use of virgin female traps demonstrated cross-attractancy between the two species. Since abdominal tip extracts of D. watersi females after gas chromatography produced the same pattern of electroantennogram responses as D. castanea female tip extract, it is probable that the sex pheromones of the two species are identical.

A total of 2609 blood-fed females of 23 species of Aedes and Culex was collected, mainly from outdoor resting sites or in unbaited suction traps, at two localities in The Gambia. The host-feeding patterns of the mosquitoes indicated by the results of precipitin tests on the blood-meals were of thiee types: those in which large mammals were the predominant hosts, those where mammals, birds and reptiles were represented and those in which avian feeds predominated. C. tritaeniorhynchus Giles had fed predominantly on cattle, and small numbers of nine species of Aedes had fed on large mammals. C. thalassius Theo. was non-specific in its feeding habits, with feeds from a wide range of mammals and birds and a few reptiles. No evidence was found for a change in the feeding habits of C. thalassius with increasing age. C. poicilipes (Theo.) also fed on mammals and birds. Birds were the primary hosts of C. tigripes Grp. Charm., C. nebulosus Theo./ C. cinereus Theo., C. decens Theo., C. invidiosus Theo. and C. neavei Theo., although the feeds of C. decens included a large proportion on bats.

Topical doses of triflumuron in acetone as low as 0.05 μg per fly induced a significant reduction in the production of viable offspring by adult Glossina morsitans morsitans Westwood, the effect being greatest in the two reproductive cycles following treatment. A dose of 0.5 μg terminated successful reproduction for the life of the fly. A single dose was as effective as the same dose split into five separate treatments. Exposure of females by tarsal contact during passage through a cotton cloth cone treated with 3% suspension concentrate of triflumuron was sufficient to terminate successful reproduction for at least four reproductive cycles following treatment. Males exposed to treated surfaces for 5 minutes could transfer effective amounts of triflumuron to females during mating for at least 2 days after treatment. Target materials, treated with 1% triflumuron in acetone and exposed to field conditions in Zimbabwe for 6 months (April to September), retained their ability to induce a peak abortion rate of 60–70% (40–45% overall) among females exposed by brief tarsal contact in the laboratory.