In Java, Brontispa longissima (Gestro) (Col., Hispidae) is represented by chr. var. javana Weise and in South Sulawesi (South Celebes) by chr. var. selebensis Gestro. The endoparasite Tetrastichus brontispae (Ferriére) (Hym., Eulophidae) attacks both chr. var. javana and selebensis. However, in Java, there are two distinct strains of chr. var. javana. In one strain (A-strain) the parasite completes its development normally but in the other (B-strain) the parasites usually die in the larval stage. The areas where each strain occurs have been demarcated.

In laboratory studies at Bogor during 1958 it was established that the lifecycles of the A- and B-strains were similar. T. brontispae completed its development from egg to adult in 15 to 21 days (16 on average) in A-hosts but died in the larval stage in B-hosts within three to four days. In a few instances parasites in B-hosts were able to complete their development, but generally the host died a few days after the death of the parasites.

In the laboratory, adult parasites attacked B-hosts as readily as A-hosts, although the former were not suitable for parasite development. Phagocytosis by encapsulation or melanisation was occasionally encountered but was not the usual cause of the death of the parasites.

A method is described for continuous rearing of Distantiella theobroma (Dist.) in the laboratory at approximately 75°F. and 65 per cent, relative humidity. Adults were caged on young cocoa twigs, and the mated females transferred to cocoa seedlings for egg-laying; 24 hours after hatching, the nymphs were transferred to unripe cocoa pods. The egg and nymphal stages lasted about 14–16 and 23 days, respectively.

The effectiveness of ten acaricides against Boophilus microplus (Can.) on cattle in southern Queensland, Australia, was investigated in 1960–63. Of infested cattle dipped in or sprayed with each acaricide, some were kept in stalls so that observations on ticks that survived treatment could be made, and others were grazed in tick-infested pastures in order to find the period of protection against reinvasion by larvae. Untreated cattle were also kept in the stalls to indicate the numbers of ticks occurring in the absence of treatment. The reproductive capacity, in terms of eggs and larvae produced, of ticks surviving treatment was compared with that of untreated ticks, and, for aldrin, dieldrin and the last four compounds mentioned below, the protective period in the field was compared with deposits of acaricide on the hair of the cattle as indicated by chemical and biological tests. For the last four acaricides, the effect on toxicity of artificially fouling the dip fluid was investigated, and also the relative toxicity of clean and artificially fouled fluids to ticks dipped in them under laboratory conditions.

The acaricides tested, and (in brackets) the concentrations used, were aldrin (0·05 & 0·1%), dieldrin (0·1%), carbaryl (0·2%), Boots' ED 12308 (0·2%), ethion (0·1%), Ciodrin (0·1%), coumaphos (0·02%), diazinon (0·05%), carbophenothion (0·086%) and dioxathion (0·075%). All were emulsion formulations except carbaryl and diazinon, which were used in wettable-powder form.

Daily collections of engorged adult ticks that fell from the stalled cattle provided clear-cut, though not quantitative, assessments of the effects of the acaricides. All the compounds tested gave a very high level of control, the only exception being the lower concentration of aldrin, and the reproductive capacity of ticks that survived treatment was negligible. With some of the acaricides, large numbers of surviving ticks fell in the first day or two after treatment, and some laid eggs; but the viability of the latter was invariably low. These observations emphasise the need to consider the reproductive capacity as well as the direct kill of parasitic ticks when assessing the value of acaricides. At the concentrations tested, nearly all the compounds allowed a few ticks to survive that were in the engorged-nymph stage at the time of treatment; these dropped off the cattle from the tenth day onwards and laid viable eggs.

The mean protective periods of the chlorinated hydrocarbons and organophosphorus compounds ranged from three to six days, but on individual animals periods from three to eight days were recorded. Amongst the carbamates, a mean protective period of seven days was recorded for carbaryl in summer, whereas the mean protective period of RD12308 in winter, when such periods are longer, was 12 days. In come cases, protection appeared to continue when deposits of the original acaricide could no longer be detected on hair samples, and reasons for this are discussed.

The influence of various factors, other than concentration, on the effectiveness of acaricidal fluids and on the results of tests was examined. Chemical and biological tests of hair samples showed that the acaricides persisted longer on stalled than on pastured cattle. Formulations affected the amount of toxicant deposited on the hair, and there was an indication that fouling of the dip fluid with soil and dung may, under certain circumstances, increase the amount of toxicant deposited.

Precipitin tests were performed on 238 blood-smears made from Culicine mosquitos collected from natural resting places at three sites, in the area surrounding a village, in uninhabited forest, and at an uninhabited rock outcrop in savannah vegetation in Northern Nigeria. In calculating the percentages of blood-meals that were positive for the various animals, the following criteria were applied: all negative results were subtracted from the totals tested; in calculating mammalian, but not avian or reptilian, percentages, all records that referred to “mammal, weak smear” were subtracted; “unidentified mammal” was included in the calculations. Results showed that Culex pipiens fatigans Wied. (taken only in the area surrounding the village) had fed mainly on man (45%) and birds (36%), and while Aedes vittatus (Big.) (taken only at the rock outcrop) fed to some extent on both man (14%) and birds (18%), the majority of blood-meals (54%) had been obtained from the porcupine (Histrix cristata). It is thought that these feeds on man from individuals of Ae. vittatus taken at an uninhabited site may have been obtained from villagers using a road about 150 yd. from the outcrop. Ae. luteocephalus (Newst.) (the majority of which were taken in forest) also fed to some extent on porcupine (11%) and birds (16%), but the principal host appeared to be Bovids (74%). It was established for the first time that Uranotaenia mashonaensis Theo. (the majority of which were taken in forest) bites man (29%); mammals other than man and birds accounted for 29 and 24 per cent., respectively. Half of the blood-smear samples obtained from females of this species did not react to any antisera, and were classified as negative.

The larva of Hylemya arambourgi Séguy is an important pest of barley in Kenya; it attacks the shoots, causing death of the central leaf. Three to four shoots are destroyed by each larva, and an early, heavy infestation, under conditions of drought, may cause complete loss of the crop. Where a crop is obtained, the effect of an infestation on yield is difficult to assess, because climatic factors play a major part in determining ultimate figures.

The life-cycle is briefly described.

Trials with various methods of chemical control showed that only seed treatments were consistently effective. Other forms of pre-sowing treatment were ineffective at economic rates of application, while a spray applied after an attack had developed was of little value. Sprays applied prior to the development of an attack gave variable results but were usually ineffective.

The most satisfactory chemicals used as seed treatments were dieldrin and heptachlor. Aldrin and endrin were sometimes effective, while γ BHC, carbaryl, dimethoate and thiometon were ineffective. A formulation of chlordane was also ineffective, but this failure may have been due to poor dispersion on the seed. It is probable that the insecticide acted mainly as a systemic poison, since larvae rarely enter the soil before the time of pupation.

Both dieldrin and heptachlor were initially used at rates of 4·6–5·0 oz. of active ingredient per 100 lb. seed, but usually gave as good results at rates of 3·5 and 3·2 oz., respectively. Dieldrin gave a measure of control at even lower rates.

The prospects for cultural methods of control appeared slight. No evidence of varietal resistance was obtained, while the possibility of control by restrictions on the sowing season is ruled out by the lack of evidence of diapause and the probability that Pennisetum clandestinum and other Gramineae, such as Chloris gayanaand Setariasp., serve as alternative hosts. For the same reasons, it is considered unlikely that any change in the position of barley in the seven-year rotation would have any effect on the level of infestation.

Crops of cowpea (Vigna unguiculata) in Northern Nigeria are normally subject to such heavy attack by insects that the potential yields are seldom realised. The most important pests are Maruca testulalis (Geyer), which damages flowers and pods, Piezotrachelus varium (Wagn.), which attacks seeds, and the Coreids Acanthomia brevirostris Stål, A. horrida (Germ.), Anoplocnemis curvipes (F.) and Mirperus jaculus (Thnb.), all of which destroy pods. Pests that attack the pre-flowering stages of the cowpea are economically less important. Field surveys showed that, in 1961, Maruca testulalis, P. varium and Coreids together destroyed 62, 92 and 19 per cent, of the potential crop of seed from sowings in June, July and August, respectively. The corresponding percentages for 1962 were 55, 75 and 29, respectively.

The effectiveness of insecticides in the control of the pests that attack after flowering has commenced was investigated in field trials at Samaru, Northern Nigeria, in 1961–63. The results showed that large increases in yield could be obtained by spray treatments starting at the first appearance of the flowers. The best of these, consisting of 1 lb. DDT with 0·1 lb. BHC per acre applied six times at weekly intervals, gave an average yield over the five trials of 1,623 lb. dry seed per acre, which is a substantial increase over the estimated national average of 158 lb. per acre. Three applications of DDT/BHC, and six or three applications of Sevin at 1 lb. per acre, gave poorer results on the whole. Insecticidal treatment reduced the incidence of all pests and led to a corresponding reduction in flower losses. It also compressed the flowering period, induced earlier flowering and pod production, and caused the bulk of the crop to mature at one time. Haulm production was also reduced, and crops grown for haulms rather than for seed should therefore not be treated with insecticides.

The effects of pockets of damp wheat upon the spatial structure (dispersion) of experimental populations of adults of Cryptolestes ferrugineus (Steph.) were investigated in the laboratory. Isolated pockets of non-mouldy wheat of 18 per cent, moisture content (85 per cent. R.H.) and of equally moist wheat supporting a mould flora (mainly Aspergillus candidus) were placed in a larger bulk of wheat of 14 per cent, moisture content (70 per cent. R.H.) at 25°C. One hundred beetles were released at the centre of the top surface of the bulk, and their dispersion within it was observed one week later. The method used allowed the entire bulk (25 kg.) to be quickly broken down so that the relative numbers of individuals in each of the 64 cubes of which it was composed could be recorded. Using other apparatus, the responses of single, isolated individuals to these physical conditions were analysed.

Insects reared at 25°C. and 70 per cent. R.H. accumulated to an equal extent in the pockets of damp wheat irrespective of whether it was mouldy or not. Insects in a preferendum arena went to the drier side, i.e., to 70 per cent, as opposed to 85 per cent. R.H., and the underlying mechanism was found to be a klinokinetic response to humidity. Maintaining insects at 40 or 85 per cent. R.H. for 14 days before testing did not alter their dispersion behaviour in bulks of grain; maintenance at 40 per cent. R.H. did not alter their response to humidity in a preferendum arena, but at 80 per cent. R.H. it was abolished.

A study of oviposition behaviour showed that when there was a choice between wheat of 18 and 14 per cent, moisture content, nearly all the eggs were laid in the damper grain, both when it was mouldy and when it was not. It is considered that oviposition requirements, and to some extent trophic behaviour patterns, over-ride the hygrokinetic response when wheat is damp or damaged, but that under field conditions, where the presence of dust and broken grain throughout the bulk provide conditions suited for oviposition and feeding, accumulations due solely to hygrokinesis may occur in the drier parts of a bulk.

The results are discussed in relation to the ecology of the species in grain and to its detection and control; and evidence from this and other studies is discussed in relation to the dynamic nature of spatial organisation of insect populations in grain.

The extent of the dependence of the foreign grain beetle, Ahasverus advena (Waltl), upon moulds in its diet was investigated.

Using a simple technique, the insect was cultured axenically at controlled temperature and relative humidity on an autoclaved mixture of rolled oats, wheatfeed and dried yeast. After the mixture was sterilised by exposure to propylene oxide vapour, virtually no larvae completed development on it in the absence of living micro-organisms, and this effect was unchanged by the addition of a mixture of B-vitamins followed by autoclaving. However, when fungi were grown on the food previously sterilised with propylene oxide, it again permitted the complete development of the insect.

Autoelaved wheat germ was not a suitable diet for A. advena unless a small proportion of dried yeast was added before autoclaving. It is concluded that living fungi are not essential in the diet of the insect, but that they may supplement an otherwise inadequate diet.

The minimum development time from egg to adult on a complete food at 80 per cent. E.H. and 30°C. varied from 18 to 25 days.

Detailed studies are described, and illustrated by photomicrographs, of the method by which the newly emerged pupae of Mansonia annulifera (Theo.) and M. uniformis (Theo.), which are important vectors of filariasis in Kerala State, India, attach themselves to the aquatic plant Pistia stratiotes. After emergence of the cephalothorax through the ruptured larval skin, the latter continues to support the pupal abdomen while this doubles over so that the respiratory trumpets of the cephalothorax are directed towards and eventually reach the point of insertion of the larval siphon into the Pistia root. The trumpets are then plunged into the hole occupied by the larval siphon, which is almost simultaneously yanked out of it by the straightening of the pupal abdomen, leaving the pupa attached by its trumpets. The pupa casts off the larval skin posteriorly and then curls round to assume the usual comma shape. The entire process occupies under one minute in M. annulifera and 3–6 minutes in M. uniformis.

Oviposition and the length of adult life in the Bruchid beetle Caryedon gonagra (F.), an important pest of unshelled groundnuts (Arachis) in West Africa, were studied in continuous darkness in incubators at 30 and 40°C. at relative humidities of 50, 70 and 90 per cent., and at 45°C. and 70 per cent., and also under conditions of diurnal alternation of periods of light and darkness in a constant-temperature room at about 27·5°C. and 75 per cent. R.H. Newly emerged beetles were placed, singly (unmated or after a single mating) or in pairs, in tubes with 1–5 unshelled groundnuts. In addition, the influence of the absence of groundnuts was investigated.

Length of life of the adults increased with decreasing temperature, increasing relative humidity, the absence of nuts (for females only) and the absence of mating (for females, and, in absence of nuts, for males). Adults survived for 3–4 days at 45°C. and 70 per cent. R.H. Optimum conditions are probably about 27·5—30°C. and 70—90 per cent. R.H., under which the adult length of life was about 21 days.

The adults were sexually mature on emergence from the cocoons, and mating took place within 24 hours of emergence. Under the conditions of the experiments, the preoviposition period was between 24 and 48 hours. At 27·5 and 30°C., the mean length of the oviposition period (9—13 days) was only slightly influenced by relative humidity, being slightly shorter at the lowest R.H. (50%); an increase in temperature from 30 to 40°C. caused a marked reduction in the period.

About 80 per cent, of the eggs were laid in crevices in the shell of the nut, where they are difficult to find. In the absence of nuts, the females laid readily between the cork and the glass and at the bottom of the tube.

At 40°C., oviposition was inhibited at 50 and 70 per cent. R.H., but at 90 per cent. R.H. many eggs (but significantly fewer than at lower temperatures) were laid; the largest mean numbers (106–115) were laid at 27·5–30°C. and 70–90 per cent. R.H.; absence of nuts did not influence the numbers of eggs laid, but caused some irregularity in the oviposition pattern. More than one copulation appeared to be necessary for the female to lay a full complement of eggs.

Under conditions of alternating periods of light and darkness, there was a daily rhythm of oviposition, with a strong correlation between numbers of eggs laid and the periods of darkness.

The results are compared with those recorded in the literature.

The inheritance of white eye in Lucilia cuprina (Wied.) was investigated by means of a series of back-crosses repeated through ten generations. Since an approximate 1:1 ratio of white-eyed: red-eyed flies was observed throughout, it is concluded that white eye is due to a single recessive gene (w). Earlier work establishing that w is on an autosome is discussed.

A test for the existence of a linkage group containing genes for white eye and dieldrin-susceptibility was then made. The exposure of back-cross progeny to discriminating levels of insecticide, and the pattern of mortality observed with scalar concentrations of dieldrin, indicated that genes for white eye (w) and dieldrin-susceptibility (rdi) are on different chromosomes.

In both a susceptible and a diazinon-resistant strain of house-flies (Musca domestica L.), adults of both sexes were most susceptible to diazinon immediately after they had emerged from the pupae. Their resistance increased for two days after emergence and remained steady for the next three days, and the increase was proportionately larger in the resistant strain. Taking flies 2 ± 2 hr. old as a basis, the increases in resistance by the third day were 1−2½ and 3½−6½ times for susceptible and resistant males, respectively, and 2−5½ and 9−18½ for susceptible and resistant females. In both strains, the two sexes were equally susceptible to diazinon during the first day, but later the females were more resistant than the males. The resistance factor (ratio of LD50's of resistant and susceptible strains) was least immediately after emergence and increased with age; it was 15–30 in flies 2 ± 2 hr. old and 50–90 three days later. There was no direct relation between changes in resistance and changes in the weight of the flies on aging. The resistance factor to diazinon should be measured not earlier than three days after emergence to obtain reproducible values. Removal of the ovaries in flies less than one day old did not affect the increase in resistance with age.

Allatectomy of newly emerged house-flies (Musca domestica L.) prevents maturation of the ovaries, and experiments were done to find whether this affected the sensitivity of the flies to insecticides.

The apparatus and operational procedure for removing the complex comprising the corpus allatum and corpora cardiaca are described.

Females of a diazinon-resistant strain (SKA) were allatectomised less than 12 hr. after emergence, and when three days old their sensitivity to diazinon, dieldrin and pyrethrum extract was tested by topical application. Approximately equal numbers of intact females were tested simultaneously, and untreated controls of both kinds of flies were included in every test. The failure of the ovaries to mature in allatectomised flies was confirmed by examination of a majority of the operated flies that lived for four days, and normal development of the ovaries of intact flies was similarly confirmed.

The results showed that there was no difference in sensitivity between allatectomised and normal flies. It is concluded that allatectomy does not affect susceptibility to the insecticides used. Since earlier work had shown that a 9- to 18-fold increase in resistance to diazinon takes place during the period from emergence to the third day afterwards, it is further concluded that this increase is unaffected by allatectomy and the failure of the ovaries to mature.

Gravid females of the red locust, Nomadacris septemlasciata (Serv.), were initially influenced by the microclimate in the selection of oviposition sites, and a laboratory investigation showed that females preferred to lay in well-illuminated areas with a soil temperature between 43 and 37°C., and avoided areas of very high surface humidity. Final acceptance of the soil took place only after the locust had probed with its ovipositor, and experiments demonstrated that particle size, compaction, moisture content and chemical composition of the soil all influenced the choice of oviposition site, while pH did not.

Experimental evidence is given to show that only two larval instars occur during the development of Meligethes aeneus (F.) (Coleoptera, Nitidulidae) under laboratory conditions in Scotland, based on the facts that there is only one moult and only one increase in head-capsule width. The egg, first- and second-instar larvae, prepupa and pupa of M. aeneus are described and compared with the corresponding stages of M. viridescens (F.). The larvae of the two species are differentiated for the first time by the arrangement of dorsal cuticular tubercles, the size and form of the urogomphi and the width of the head capsules.

One of the principal pests of cowpea (Vigna unguiculata) in southern Nigeria is Laspeyresia ptychora Meyr., the larvae of which attack the seeds within mature pods and cause considerable loss of yield. It has not so far been recorded from northern Nigeria. Details of the life-history of this Eucosmid are described from laboratory and field observations made in Nigeria in 1962–63. Eggs are laid on mature pods, which the larvae enter very soon after hatching, feeding on the seeds within. Pupation normally takes place in a cocoon in the soil, but pupal development can be completed in the absence of soil and of a cocoon. Four generations normally occur on the two crops of cowpea that can be grown each year in southern Nigeria, a complete first and a partial or complete second generation on each; but five generations may sometimes occur. The pest survives through the dry season and between the two crops in the rainy season by means of generations that develop on stand-over and volunteer cowpea, on leguminous plants grown in market gardens, and possibly on some yet undiscovered wild plant. No diapause in any stage was observed.

Annual fluctuations in larval populations and levels of infestation are described in relation to the cowpea crops and to the damage caused. In a field trial in 1963, 35 per cent, (by weight) of seed from the early crop and 20 per cent, of that from the late crop was damaged. These figures take no account of seed that was completely destroyed, so that the true losses are greater than they indicate. Damaged seed is usually unmarketable as a result of contamination with frass and webbing.

Investigations showed that, although larvae may be carried into stores when the crop is harvested, L. ptychora cannot become a pest of stored cowpea seeds because it is unable to develop on dried seeds.

The possibilities of chemical, cultural and biological control are discussed, the latter not at present being promising. Field trials with γ BHC, dieldrin, carbaryl, isobenzan and phosphamidon were carried out; only the last-named, which is a systemic insecticide, showed promise of affording satisfactory control. The difficulties of successfully attacking L. ptychora with insecticides are discussed, and it is concluded that chemical measures will need the support of modified cultural practices, particularly those directed towards destruction of stand-over and volunteer cowpea plants, if a satisfactory level of control is to be achieved.

The life-cycle of five stocks of Cadra cautella (Wlk.) (Phycitidae) and the duration of the various developmental stages were studied at temperatures from 15 to 37·5°C. and relative humidities between 0 and 100 per cent, on a mixture of wheatfeed, wheat germ and yeast. At 70 per cent. R.H., the limiting temperatures for the completion of the life-cycle were about 15°C. and about 36°C. At 30°C., the limiting humidities were about 20 and above 90 per cent. R.H. Development was quickest at 30–32°C. and 70–80 per cent. R.H., taking 29–30 days from the laying of the egg to the formation of the adult moth. This period increased with lower temperature and humidity, reaching 145·0 days at 15·5°C. (70 per cent. R.H.) and 51 days at 20 per cent. R.H. (30°C.).

Near the optimal conditions for rapid development, the egg occupied about 10 per cent, of the developmental cycle, the larva about 70 per cent, and the pupa 20.

Temperature influenced the duration of all developmental stages, but humidity had a marked effect only on the larva. The pupation of some mature larvae was delayed: whether or not this delay is a diapause is discussed. Virgin adults lived 4·8 days at 35°C. to 18·9 days at 17·5°C. (70 per cent. R.H.). At 30°C., low humidity halved the length of adult life.

The mortality, even in favourable conditions, was often rather high, principally among eggs and young larvae.

There was poor survival of small numbers of larvae kept on maize and on cocoa beans, but survival on wheat was similar to that on the usual food mixture. The developmental period on wheatfeed alone was shortened by the addition of honey or glycerine or a combination of wheat germ and yeast.

The incidence of disease is discussed.