Anthrenus flavipes Lec. (vorax Waterh.), commonly known as the Furniture Carpet Beetle, is a widely occurring species of wool-destroying insect in India. It feeds on woollen materials, feathers, bristles, furs, horse-hair, horny substances and other materials of a keratinous nature. The adult beetles feed on pollen and nectar of flowers in nature and are harmless; and it is the larva which destroys the above materials. The life-history of the pest has been studied at several controlled levels of temperature and humidity, and also in a room where the humidity was controlled at 70–75 per cent. R.H. and the temperature fluctuated between 25 and 31°C. over the year. The results are compared with those of earlier authors. The sex-differentiating characters have also been investigated in the pupa and adult.

Temperature influences the duration of the egg stage and the viability of eggs. The incubation period of eggs at 25, 30, 25 to 31, 35 and 37·5°C. is about 13, 8, 7, 6 and 4 days, respectively. The viability of eggs is greater at 25 to 31, 35 and 37·5°C. than at 25 and 30°C. The fluctuating temperature (25 to 31°C.) has a more favourable effect on the incubation period and viability of eggs than the constant temperatures of 25 and 30°C. Humidity, however, has no effect on either the duration of the egg stage or the viability of eggs.

Temperature has a marked effect on the total larval period and to a lesser extent on the number of larval instars. The larval period is appreciably less at 25 to 31°C. and 35°C. than at 30°C. The number of larval instars is greater at 30 and 35°C. than at 25 to 31°C. though the duration of each instar is less at 35°C. than at 25 to 31 and 30°C. The fluctuating temperature (25 to 31°C.) is more favourable to rapid larval development than the constant temperature of 30°C. and also reduces the number of instars. Humidity has no effect on the number of larval instars and the total larval period.

Larvae thrive most satisfactorily on woollen fabric treated with 10 to 20 per cent, commercial yeast.

The duration of the pupal period and the number of adults emerging are dependent on temperature. The pupal period is about 14, 12, 9 and 7 days at 25, 25 to 31, 30 and 35°C. and is nearly the same for the male and the female. Humidity has no effect on the pupal period. These results are discussed in relation to those of earlier workers.

The pre-emergence (quiescent) period extends over 7 to 9, 7 to 8, 6 to 8 and 5 to 6 days at 25, 25 to 31, 30 and 35°C., respectively, irrespective of sex. Humidity has no appreciable effect on this period. These results are at variance with those reported by earlier workers.

The length of life of the adults is dependent on temperature but humidity has no appreciable effect on this period. The nature of food influences the length of life of the adults. A female starts laying eggs 4 to 10 days after emergence, depending upon temperature and humidity, and lays 12 to 41 eggs. The sex ratio between male and female was found to be 0·8:1.

The entire life-cycle is shortest at 35°C. Under conditions similar to those of the experiments described, there are one to one-and-a-half generations of the insect in a year depending upon the temperature conditions.

Results are given of laboratory trials of insecticides, carried out in Kenya, against two pests of agricultural crops in East Africa. Against Epilachna hirta (Thnb.) (Col., COCCINELLIDAE), the adults and larvae of which feed on the foliage of wheat and other crops, dusts containing 0·5 or 2 per cent, parathion, applied at rates to give 0·74 to 2·97 mg. active ingredient per sq. ft., were the most rapidly effective against the adults. A 5 per cent. DDT dust, at rates giving 0·36 to 5·82 mg. technical DDT per sq. ft., was less rapid in action but produced very good results by the end of three days. A proprietary BHC dust, used at rates giving deposits of from 0·23 to 1·04 mg. γ isomer per sq. ft., was less effective and, at the highest rate used, only reached 100 per cent, mortality after eight days.

Several insecticides were tested in emulsified solutions against Cylas puncticollis Boh. (Col., CURCULIONIDAE), one of the important sweet-potato weevils of East Africa. All the insecticides were applied at concentrations of 0·02, 0·1 and 0·5 per cent, active ingredient, and at a deposit rate of 0·813 mg. of spray per sq. cm. DDT was the most effective after 18 hours, but γ BHC was only slightly inferior.

An apparatus for exposing insects to known concentrations of vapours from odorous liquids is described; it was used in a laboratory in England to test adult tsetse flies, Glossina palpalis (R.-D.) and G. morsitans Westw., obtained from Africa as pupae, and the blowfly, Phormia terraenovae R.-D. There is a definite pattern of behaviour of the flies in olfactory stimulants, in the final phase of which they are excited to fly. The number of seconds for which a fly is in flight gives a measure of its activation by the vapour. The method gives results comparable with those obtained with a standard choice-chamber technique and has considerable practical advantages for work with tsetse flies. The effects of concentrations of vapour, period of exposure, condition of the flies and external conditions on the response of tsetse flies to vapours were studied.

The response of G. morsitans and P. terraenovae to a selection of aliphatic acids, alcohols, esters and amines was determined, using a standardised procedure. There is a marked similarity between the two species in the concentrations of vapours required to activate them. The standard molar concentration, defined as the concentration of vapour required to raise the activity of the flies to a standard level of ten times that in pure air, was calculated for each compound tested from the regression of activity on concentration. Threshold concentrations (the highest concentrations that failed to raise fly-activity) were also calculated from the regression equations.

The laboratory rearing of all stages in the life-history of the Wheat Bulb Fly, Leptohylemyia coarctata, (Fall.), is described. The object of this work was to provide suitable material, in particular eggs and larvae, for insecticide experiments. Details of a container suitable for ovipositing adults are given. Several diets for the adults were compared and it was found that the greatest number of eggs was produced when the flies were fed on beef blood and a mixture of sweetened condensed milk and honey. Females were found to lay up to 244 eggs each; egg-laying commences 9–15 days after emergence and continues almost as long as the females live, but reaches a peak 3–5 weeks after emergence. Some females survived from late June until early November. In a small laboratory population, the average number of eggs laid by each female was 29·9 and mean length of life was 26·3 days for males and 41·6 days for females.

The eggs have a long obligatory diapause period. They have no effective water-proofing mechanism, but can recover from considerable temporary desiccation. A method of storage during diapause is described. The eggs normally hatch in late January or early February, but hatching can be delayed until much later in the year by storage below 0°C.

The effects of temperature on larval and pupal development are described. Larvae will grow at 20°C., but pupating larvae or young pupae are rendered sterile unless kept at temperatures of 15°C. or below. It is shown how a combination of delayed hatching and rapid larval and pupal development can produce fertile flies at unusual times of the year in the laboratory. It is suggested that this may make it possible to produce young larvae in the autumn for insecticide experiments.

In conclusion, some parasites and predators encountered in the field and the laboratory are mentioned.

The effects of exhaust gases and distillates of sump oil from old motor cars on the activity of Glossina palpalis (R.-D.) were briefly investigated, using a method described in the preceding paper. The exhaust gases had no effect on the tsetse flies and the threshold and standard concentrations of vapour of distillates from sump oil required to stimulate the tsetse flies decreased as the boiling point of the fractions increased. This result is consistent with the results of experiments by previous workers using series of homologous pure compounds, and suggests that any very stimulating compound could only be present in very small quantities in sump oil.

The loss of crop following insect attack on cotton was studied in 1950–54 at the Cotton Research Station, Namulonge, which is situated in the elephant-grass zone of Uganda, in which the principal pest of cotton was originally considered to be Lygus vosseleri Popp. In 1953, the main invasion of cotton by Lygus occurred during September and October, originating from cultivated crops of black gram (Phaseolus mungo) and sorghum and from the wild perennial legume, Pseudarthria sp., which earlier workers had considered important. Trials in this zone have demonstrated, over a number of years, that early June is the optimum date for sowing cotton, although such sowings receive the heaviest attack by L. vosseleri. Experiments to determine the maximum loss of yield due to Lygus should therefore be made with cotton sown at this time. Bollworms are also important pests, notably Heliothis armigera (Hb.) and Earias spp., their attacks following those of Lygus and being heaviest in October–November.

A detailed account of the biology and development of an important parasite of cockroaches, the Evaniid, Evania appendigaster (L.), is given. Adult and immature stages of the parasite were obtained and studied from collections of oöthecae of Periplaneta americana (L.) made in Saudi Arabia, some 25–29 per cent, of which were parasitised. There are at least three or four generations a year, a rate of multiplication which gives the parasite a very decided advantage over its much slower-breeding host (P. americana takes at least a year or more to pass through one generation).

The Evaniids are a neglected group of parasitic Hymenoptera and so far very little has been published about them.

Adult parasites emerged from the material collected in Saudi Arabia in or about February, May and October. Oviposition in this species is carried out in a rather peculiar manner. The female lies on her side and, with legs braced against the oötheca, penetrates the tough integument of the egg-capsule after about half-an-hour's hard labour. Only one egg (hymenopteriform type) is laid in an oötheca, and the larva which develops from it is solitary in habit, and completely devours all the eggs in the egg-capsule of its host. The number of larval instars was determined by an examination of the cast skins in the residual material of parasitised oöthecae, a task rendered easier by the very distinctive mandibles of the various stages. Altogether there are five separate larval instars, the first easily identified by the serried arrangement of small denticles on the mandibles. The mandibles of the next two stages are tridentate and shaped like a gauntlet glove, while those of the last two instars are sub-triangular and bidentate. The mature larva is described in detail, and recognition characters for eggs, larval instars and adults are provided.

An appraisement of the value of the two important parasites, Tetrastichus hagenowii (Ratz.) and E. appendigaster, in the biological control of cockroaches is made. It is pointed out that T. hagenowii in certain areas destroys from 15–57 per cent, of the eggs of its host and E. appendigaster 25–29 per cent. Both the former, with up to six generations a year, and the latter, with three or more, multiply much more rapidly than their host. Between them the two parasites appear to be capable of destroying up to 50 per cent, of the cockroach population.

The host records and general distribution of five species of Evania, one each of the related genera Prosevania, Zeuxevania and Brachygaster, and two of Hyptia, all of which parasitise the oöthecae of cockroaches, are fully documented. E. appendigaster itself has been recorded from the main species of cockroach, P. americana, P. australasiae (F.), Blatta orientalis L., Cutilia soror (Brunner) and Neostylopyga rhombifolia (Stoll), and its distribution ranges from Europe (Hungary) and the Middle East (Palestine) to the Pacific (Hawaii and Fiji), America (Gulf and Atlantic States), and the West Indies (Jamaica).

Experiments with second-, third- and fourth-instar larvae of Aëdes aegypti (L.), as well as pupae, were carried out to determine their behaviour in temperature and light gradients in an experimental trough.

When second-instar larvae are subjected to a temperature gradient from 42°C. at one end of the trough to 8°C. at the other, the majority of larvae aggregate over the range of temperature 23–32°C. Third- and fourth-instar larvae and pupae, however, show a marked preference for the range of temperature between 28–32°C.

When subjected to a light gradient from 1·08 log foot-lamberts to log foot-lamberts, second- and third-instar larvae show no marked preference for any one light intensity. The majority of fourth-instar larvae, however, aggregate in the darkest region of the trough, and this negative phototactic reaction is very pronounced in the pupae. This behaviour is probably correlated with the development of sense organs as the larvae grow. In the case of light gradients, it is likely that the increasing negative phototactic reaction is due to the increasing sensitivity of the imaginal compound eye which starts developing in the early larval instars and reaches an advanced stage in the pupa.

The study of crop loss following insect attack on cotton in Uganda, described in Part I of this work, was continued for two further seasons (1954–56), using the same experimental procedure, except that half the DDT in the spray formulation was replaced by toxaphene, only three periods of protective treatment were used for each date of sowing, and the late-season ones were continued until boll-opening was complete, so as to give maximum control of boll worm.

Methods are described of estimating an index of leaf damage caused by Lygus spp., based on comparisons with standard grades. At Serere (Eastern Province), the index of leaf damage was closely related to Lygus populations in the crop, and at Namulonge (Buganda) it was markedly reduced on plots protected from Lygus attack, but in the 1954–56 experiments no relationship could be found between the mean seasonal index and the loss of fruiting bodies attributable to Lygus attack, or the final yield.

Analysis of the cause and incidence of shedding of developing fruit bodies (flower buds or young bolls, the latter predominating among those recovered) showed that the total amount of shedding was roughly the same whatever the treatment, that due to insect damage tending to be balanced by that due to other causes, which were probably physiological in nature. There was thus some over-riding factor, other than pest attack, that governed the crop finally held by the plant.

Damage caused by insects to older bolls, which do not shed, constitutes a real loss that is reflected in the final harvest. The proportion of clean seed cotton was higher in the treated plots, particularly in the early-sown cotton, in which analysis of the harvested locules showed that the damage was predominantly due to bollworm, but there were no significant differences in yield between the various treatments in either date of sowing or in either season.

It is concluded that under such conditions as those experienced at the Research Station in the three seasons of the experiments, insect damage to cotton is small in relation to other environmental factors governing crop production.

Four different methods of marking insects are described in detail. Although they have been applied by the present authors only to the British Calliphorinae, they should be of value in ecological studies of mobile arthropods in general. These methods are: individual marking with paints, mass powdering with dyes, radioactive labelling with 32P, and a combination of the last two. A fifth method, in which the emerging fly labels itself with fluorescent dust, is briefly described. The circumstances affecting the choice of method are outlined.

A new method of extracting free-living arthropods and molluscs from rough, matted grassland has been developed which gives extraction rates that are usually above 95 per cent. Its advantages over other known methods, especially sweeping, are that it is less liable to personal error, collects from otherwise inaccessible places in the habitat, permits selection of places within the habitat (e.g., tops and bases of grass) and does not depend on removal of parts of the habitat.

The apparatus consists of a light, portable but powerful electric suction pump of standard pattern, with a special compartment, containing a small collecting bag, fitted between the fan intake and the flexible hose that carries a nozzle 1 in. in diameter, which is inserted into the grass. It can be operated on several hundred yards of cable.

The sample obtained comprises a mass of plant matter and detritus from which the animals are easily sorted by hand in the laboratory.

The method is unsuitable for subterranean arthropods or for insects living inside or otherwise firmly attached to plants. But it should be possible to use it for a variety of habitats other than grassland.

Three aerial applications of the n-butyl ester of 2,4,5-trichlorophenoxyacetic m acid (2,4,5-T) in diesel oil were made at intervals of six weeks to an isolated woodland community on a peninsula in Lake Victoria, Kenya. The woodland contained two species of tsetse fly, Glossina pallidipes Aust. and G. palpalis (R.-D.) (subsp. fuscipes Newst.). The object of the treatment was to defoliate the woodland in order to ascertain whether the reduction in shade would control the tsetse fly. It was also desired to obtain further information on the effect of the spray applications on the woody plant species.

The first application, at an estimated actual dosage of 2·2 lb. 2,4,5·T per acre, resulted in a rapid defoliation of 13 out of the 15 observed leafy species, eight of, which subsequently died during the following nine months. Two succulent species of Euphorbia also died during this period. Of the remaining two species, one was fully defoliated only after the third application but recovered slowly, while the other, Lecaniodiscus vaughaniae, was but slightly affected at any time.

No significant reduction in the numbers of tsetse fly was observed during the nine-month period following the first spraying. The following factors probably account for this lack of effect: the varying rate of defoliation of the different plant species, the resistance to the spray of one locally abundant species, the persistent shade cast by the stems of the thick vegetation after defoliation and the relatively humid climate during the period of maximum defoliation. These factors allowed an environment favourable for the tsetse fly to exist in one part or another of the peninsula in spite of the severe effects on the vegetation.

Nine months after the first spraying, between a third and a half of the vegetation was destroyed during the dry season by an accidental fire. The effect on G. pallidipes was almost immediate, and two months later the population had been reduced to a fairly low level, which was maintained for the last 16 months of the experiment. The fire hardly affected the environment of G. palpalis and the main effect of defoliation was to cause this species to concentrate near the shady lake shore, where the dominant tree was Lecaniodiscus vaughaniae.

There is little doubt that the destruction of the vegetation by fire was made possible by the effects of the spray applications, as the hitherto evergreen thicket would normally have been unburnable. While this suggests a possible new technique for bush clearance, further trials have indicated several factors which may make difficult a satisfactory burn following defoliation.

Details are given of the assessment of the spray droplet performance both in calibration trials and during the applications to the peninsula.

Earlier investigations of the effects of extreme temperatures on different stages of Aëdes aegypti (L.) were supplemented by studies of eggs, larvae and pupae in water, and of eggs and adult females in air at various relative humidities.

Larvae of the same stage, young pupae (defined as those less than half-an-hour old) and old pupae (at least 36 hours old), in groups of 100, 25 and 25, respectively, were kept for various periods at low temperatures in incubators, or, at high temperatures in glass cylinders closed at their lower ends by cloth filters and inserted into water baths, and then transferred to water at 28°C. and the mortality determined from the numbers surviving 24 hr. later (in the case of larvae) or becoming adult (in the case of pupae). Eggs in batches of 1,000 were similarly treated, except that periods of 24 hr. in water at 28°C. with yeast as food added were alternated with 24-hr. periods of drying, and mortality determined on the number that hatched and survived to the third or fourth stage. Adult females (four days old) were exposed in groups of 50 for various periods in jars over appropriate solutions giving a complete range of relative humidities and kept at low, medium and high temperatures. Eggs in batches of 1,000 were subjected to the same treatments. The adults were kept at 28°C. and 60 per cent. R.H. before treatment and for 24 hr. afterwards and mortality then determined. Mortality of eggs was determined after alternate 24-hr. periods of wetting and drying at 28°C., as in the case of eggs treated in water. The results of all the experiments were expressed as the exposure-times required to give 50 per cent. mortality (T50), calculated from the observed data.

The Carnation Fly, Hylemyia brunnescens (Zett.), which attacks cultivated species of Dianthus, has been studied in detail because the account given by Bruneteau (1930) was incomplete and that given by Séguy (1932) of two flies (H. brunnescens and H. cardui (Mg.)) on carnations was also incomplete and the identities of the stages studied were not fully established. For the first time, the development of H. brunnescens from egg to adult has been completed under observation and bred adults have been maintained in captivity until eggs were laid. The eggs, larvae and adults are described.

Eggs were laid in autumn. Oviposition began in the field on 7th September 1954 and on 12th September 1955 and eggs were present until early November. The behaviour of flies in captivity confirmed that eggs were laid only in autumn.

The larvae mined in the leaves and shoots. Early larvae finished feeding in November and entered the soil. Late larvae remained on the plants and fed intermittently through January and February, whenever the temperature was suitable. Mature and immature larvae on the plants survived exposure to severe frosts. Hibernation took place in the larval stage in the soil or in the feeding sites. Pupation occurred from mid-March to mid-April and the pupal stage lasted about eight weeks.

The emergence period for 122 flies was 4th–20th June 1955 with a peak period from 6th–12th June; other observed emergence periods were 30th May–4th June (1950), 2nd–9th June (1953) and 16th–26th May (1954). Captive flies lived from two to four months. They were active during the summer but they did not reach sexual maturity and begin to lay eggs until late August. There is thus only one generation a year and the slow development to sexual maturity ensures that the larval period occurs in autumn when the foliage of the host-plants is freshest and most abundant.

A comparison is made of the populations of mealybugs, ants, predators and parasites on cacao growing in dense secondary bush and under well-cultivated conditions in Ghana, West Africa. The percentage of cacao trees infested (termed the infestation rate), the number of colonies and the populations of the vectors were similar under the two cultural conditions. Populations of ants of the genus Crematogaster and of COCCINELLIDAE were higher in bush areas than in cultivated ones. Populations of ants of the genus Pheidole, though smaller than those of Crematogaster, were greater in areas of well-maintained cacao.

Correlations of infestation rates and populations were compared under the two cultural conditions for mealybugs, ants, predators and parasites. The field data showed an exponential relationship between these factors, which was rendered linear by suitable transformations. The correlation of mealybug populations with infestation rate and with populations of parasites and predators was equally high in both habitats. The correlation of mealybug populations with those of Crematogaster was closer in the bush than in well-maintained cacao, but the implications of this are not fully understood.

There was a higher infestation rate of cacao during the first three months of the year. In contrast with previous work, the present survey has demonstrated significant changes in the vector population during the year, of a five- or six-fold order. These seasonal changes are based on mean mealybug populations per infested tree, and were largely the result of changes in the numbers of colonies; populations showed a decline during the first six months of the year and then rose to a maximum during October–November. The data suggest that these trends may be brought about largely by changes in the abundance of predators and parasites.

Trials were carried out, at two places in Tanganyika, on the underground storage in sealed pits of maize of high moisture content. The average moisture content of the maize when placed in the two pits was 16·9 and 14·8 per cent., whilst the general level of insect infestation was very light and fairly light, respectively. The predominant species was Calandra oryzae (L.); Oryzaephilus surinamensis (L.) and Tribolium castaneum (Hbst.) were also present.

The maize was kept in the sealed pits for 144 and 374 days, respectively. Samples taken at intervals showed that the insect infestation died out early, and there was no increase in insect damage. Other changes, unconnected with insect infestation, took place, and conditioning and admixture of a more palatable maize was necessary before grain from the pits could be offered to the public.

It is concluded that long-term underground storage of maize of high moisture content is not a practical proposition under tropical conditions owing to the deterioration that occurs in the grain.

The biased nature of the catches of Glossina swynnertoni Aust. made on fly-rounds at Shinyanga, Tanganyika Territory, which show an unduly low proportion of females, nearly all of which are hungry, and lack of knowledge of the fly's habits when inactive, has led to a search for resting flies.

Previous recorded observations on resting tsetse flies are briefly reviewed. These show that the resting sites chosen differ according to species and even within a species. Differences of the second kind probably reflect seasonal changes.

When larvae of Pieris brassicae (L.) were fed on leaves of plants showing symptoms of deficiency of nitrogen, phosphorus, potassium or iron, some or all of the following effects were recorded in each experiment: —

Reduction of larval weight (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).

Reduction of relative growth rate (deficiency of (1) N throughout larval life, (2) Fe from time of hatching, from sixth day and for last two larval instars).

Increased larval mortality (deficiency of N, Fe from time of hatching).

Delayed pupation (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).

The more detailed experiments with iron-deficient diet showed that similar effects were produced at whatever stage of larval development it was first supplied.

Larvae fed on iron-deficient leaves from the time of hatching appeared to have received a severe initial check to growth, but this was followed by some degree of recovery so that they showed a higher relative growth rate, a few days later, than larvae given the same diet six days after hatching.

Preliminary trials were made on the effects of the addition to diets of iron-deficient leaves of various nutrient substances sprayed on to them. No markedly beneficial results were noted.