Among a number of insects sent in for identification by Dr. J. J. H. Szent-Ivany, of the Department of Agriculture, New Guinea, were several species of weevils that are reported as causing serious injury to cacao and coffee plants. Four of these are described below, and the types have been deposited in the British Museum (Natural History).

The paper includes a review of the published literature on the biology of the Cigarette Beetle, Lasioderma serricorne (F.). A list is given of foods on which this species has been found breeding. Information on the duration of the various developmental stages is tabulated and the data on oviposition are summarised. Observations are collected together on the rate of increase of the species in warehouses, on the number of generations per year, on sex ratio, on the use of traps to catch adults and on the spread of the pest and the damage that it causes. The lengths of exposure to various high and low temperatures that are required to give a complete kill of the species are tabulated, and the known natural enemies are listed.

Original work includes a morphological comparison of L. serricorne and the closely related common storage species Stegobium paniceum (L.). The experimental work consists of a study of the life-cycle of L. serricorne on wheatfeed over a wide range of combinations of constant temperature and humidity. Development was possible from just under 20°C. to 37·5°C. at favourable humidities. Larvae died at 90 per cent. R.H. at 37·5°C. The lower humidity level for development was under 25 per cent. R.H. at 30°C. but change of temperature, both up and down, raised the lower humidity limit so that, at 20°C. and 37·5°C., all larvae died at 40 per cent. R.H. When fed on foodstuffs such as groundnuts, which contain less water than wheatfeed at all humidities, the effects of low humidity are more rigorous. The effect of a number of foodstuffs on the length of the developmental cycle was investigated. The duration of larval instars on wheatfeed at 30°C. and 70 per cent. R.H. was found. The adults obtained in the experiments were weighed. The heaviest insects were obtained at 25°C. and 100 per cent. R.H. Higher temperatures and low humidities reduced weight. Females were heavier than males. The sex ratio was unity.

The oviposition rate was investigated at 70 per cent. R.H. over a wide temperature range. Under all conditions the eggs were laid quickly. At this relative humidity, no fertile eggs were laid at 37·5°C. and few pairs laid at 20°C. The total number of eggs laid per female at 20°C. was low, otherwise temperature had little effect on the number of eggs laid, but the rate of oviposition was increased by high temperature. The theoretical rate of increase at 70 per cent. R.H. was calculated for several temperatures and shown to increase with temperature up to 35°C.

The conclusions on the distribution and multiplication of the species which can be drawn from the laboratory results are discussed.

The genus Pseudodoniella was proposed by China & Carvalho (1951) for the species pacifica from Keravat, New Britain. Recently two more species have come to hand, from Lae, New Guinea and Popondetta, Papua. They are new and are described and figured here. It has been found that in the genus Parabryocoropsis China & Carvalho (1951), two of the species then described, cheesmanae from Kokoda, Papua and duni from Keravat, New Britain, were incorrectly placed and should have been assigned to Pseudodoniella.

Fourteen species of SIMULIIDAE (of which one occurs in two forms) are recorded from Northern Nigeria. Localities for each species are given on distribution maps. Most of the species are of fairly general occurrence in the Ethiopian Region, although Simulium kenyae De Meillon is recorded for the first time from West Africa. No new species was found in an extensive survey of about 200,000 square miles.

Some notes are included on the breeding habits of the species, particularly the type of breeding site preferred, the altitudes at which breeding occurs, and the months in which immature stages have been found.

Some discussion is given of the distribution of SIMULIIDAE in Northern Nigeria and the factors which appear to influence it, partly illustrated by maps. The most important factor is thought to be the geology of the country, which determines the areas of rivers suitable for breeding. Other factors such as climate, altitude, or vegetation zones, seem to play little part, except in the far north.

Two tons of cocoa, in 32 bags, stacked in a typical cocoa store in Ibadan, Nigeria, were sampled from December 1953 to the end of April 1954. The weekly catches on “ até “ strands hung round the stack suggested that Ephestia cautella (Wlk.) was the most numerous insect on cocoa, but spear samples of the beans, taken from the sacks every two weeks, showed that the actual population of this species in the beans was small throughout the season, with no sign of build-up. Lasioderma serricorne (F.), on the other hand, was shown to be the most serious pest, the population in the beans increasing steadily from an extremely low level. It is estimated that on the average it is not safe to store initially good cocoa for more than 25 weeks in the main crop season.

Two of the species in Callosobruchus, C. maculatus (F.) and C. analis (F.), are compared and redescribed, together with a description of the male and female genitalia of both species. The species Bruchus vicinus Gylh., B. ornatus Boh., B. ambiguus Gylh., B. sinuatus Fhs. and B. quadrimaculatus F. are shown to be synonymous with C. maculatus (F.). Bruchus jekeli Allib. and B. glaber Allib. are almost certainly synonyms of C. analis (F.), but this could not be verified as no type specimens are available.

The two isomers demeton-O and demeton-S which occur as a mixture called demeton in the commercial insecticide Systox act on Aphis fabae Scop. as contact and systemic insecticides and as fumigants.

When applied as a contact insecticide or systemically via the roots from solution or from soil, demeton-S was about ten times as toxic to Aphis fabae on broad beans as demeton-O. Using demeton-S containing 32P it was shown that, when applied to the roots, radioactive material passed to all parts of the plants and that the concentration in the aerial parts was higher than in the roots. Leaf samples were more active than stem samples. By radioassay and by the cut tap-root technique it appeared that the lethal dose of demeton-S was equivalent to about 1·0 mg./kg. of fresh plant tissue. The lethal dose of demeton-O by the cut tap-root technique was 3·0 mg./kg. From solutions, the plants first absorbed demeton-S preferentially, then water preferentially. Demeton-S was more rapidly absorbed from sand than from soil.

Both isomers were translocated from older to younger leaves of broad beans usually in sufficient quantities to kill Aphids but the results were more consistent with demeton-S. The quantity translocated downwards was small. A low light intensity before and after treatment reduced the quantity of demeton-S translocated. There was also a reduction in the quantity translocated when the plants were only shaded before treatment. One day of shading was sufficient to cause the maximum reduction.

Solutions of the two isomers gave off toxic vapours and plants treated via the roots gave off toxic vapours from the foliage.

The structure of the shell of eggs of Pieris brassicae (L.), together with changes in it and associated membranes during embryonic development, have been investigated in relation to the penetration and toxicity of simple chemicals. The rigid outer shell consists of two proteinaceous layers, covered externally by a relatively hydrofuge cement, by which the egg is attached to the leaf surface. The egg has respiratory pores over its surface, and a single apical micropyle penetrating these layers. The inside of the rigid shell is lined with a layer of unsaturated oil—an unusual feature for an insect egg. When the egg is first laid, the vitelline membrane is directly applied to the inner surface of the solid shell over the region immediately around the micropyle, but within four hours this contact is broken, and the oil layer flows into this region also, and becomes complete. As development proceeds, the vitelline layer is replaced by membranes of embryonic origin, but before eclosion both these epembryonic layers, and also the oil, are resorbed.

The egg is remarkably resistant to water-soluble poisons which have no oil-solubility, except during the first four hours of development. This resistance is attributed almost entirely to the oil layer, and the early susceptibility to its absence over the micropylar region. These changes are not reflected in the effect of oil-soluble poisons or fumigants. The solid portions of the shell do not seem to be of great importance in restricting the entry of liquid poisons, even though the cement is comparatively hydrofuge; from experiments with wetting agents and with eggs immersed in poisons under vacuum, it does not appear that the respiratory air spaces in the shell are preferential channels of access; rather, the poisons penetrate through the solid portions of the shell. This penetration, even of oil-soluble materials, is slow, for they can be effectively washed out of the shell again, some considerable time after dipping. On the other hand, non-volatile oily materials can interfere with the respiration of the egg by blocking the air spaces in the shell.

The secretion of epembryonic layers does not appear to change the resistance of the egg to water-soluble materials; this is to be expected, for they do not contain lipoid. On the other hand they do add appreciably to the resistance to oil-soluble materials. There is no evidence that poisons are accumulated in these epembryonic membranes, and released during the pre-eclosion period. Experiments with covalent compounds, such as mercuric chloride, suggest that their oil-solubility accounts for their toxicity, whereas electrovalent compounds containing similar heavy metals are only effective while the direct micropylar path of entry is available to them.

Previous work has shown that, under natural conditions in the Lake District, larvae of Phyllopertha horticola (L.) hatch in early July and feed actively on the roots of pasture plants during the next 3½–4 months, undergoing two moults. They then empty the gut and enter hibernation, pupating the following spring. Stores of organic material in grass roots are at their highest level during this autumn feeding period. It has also been shown that the egg production depends almost entirely on the weight of the hibernating larva or of the pupa, which thus plays an important part in determining the reproductive rate of the population, and studies were accordingly made on larval growth and certain factors affecting it.

Newly hatched larvae were cultured at 15°C. in moistened plaster-of-paris containers filled with a mixture of soil and germinating grass seeds. They moulted at about 20 and 45 days after hatching, and stopped feeding and entered hibernation at about 100 days. When the seeds were scattered on the soil surface, larval growth was slower. The mean larval weight, plotted against age, gave a sigmoid curve; in the. first instar and most of the second, the rate of increase in weight was proportional to the weight, but thereafter, up to the time of hibernation, it was more or less constant. The rate of growth of the individual larva was irregular, being slower at the moults and variable even in the middle of the instar.

Larvae cultured under semi-natural conditions in pots of growing grass in the open moulted about 3–4 and 7–9 weeks after hatching and entered hibernation at 100–120 days. Growth is possible on a wide variety of food plants, larvae cultured on 13 species of pasture plants grown in pure stands surviving to the hibernation stage on all but two of them.

During hibernation, the larva loses 20–25 per cent, of its weight, mostly in the first few weeks. The pupal weight is almost constant and does not appear to be affected by the temperature treatment of the hibernating larva. It is thus a useful index of effective larval growth.

The mean and (in brackets) range of the weights of all pupae collected in two fields in the Lake District between 1950 and 1953 were 139·3 mg. (65–242) for males and 171·3 mg. (72–310) for females. Field samples of hibernating larvae and of pupae show considerable variation in weight from place to place, from year to year and within apparently homogeneous areas.

Variation in the time at which larval growth takes place is a major cause of variation in pupal weight. The growth period of larvae in a field at Buttermere was three weeks earlier in 1952 than in 1950, though of the same duration, and the resulting pupae in 1953 were heavier than those in 1951. Two lots of larvae of similar parentage, grown in adjacent plots of grass out of doors, one of which both hatched and entered hibernation three weeks before the other, likewise showed a difference in weight at hibernation, the earlier lot being the heavier. A series of weighed samples of larvae taken from part of a field at Ambleside in 1953 at weekly intervals during the period when they were entering hibernation showed that heavier individuals did so before lighter ones, and males before females. Factors inducing mortality during this period thus operate selectively against females, because these are exposed to them for longer.

Field-collected larvae fed in the third instar on roots of lettuce produced pupae the following spring that were significantly heavier than those from larvae fed on roots of either ryegrass or clover.

There is no evidence to show that population density affects the weight of the hibernating larva or the pupa. On the other hand, larvae from soil from which the damaged turf had been stripped by birds were significantly lighter than those from the surrounding undisturbed sward.

When moving through the soil, larvae may meet and fatally injure each other by an undirected “ snapping ” reaction. This mechanism may limit population density. In an experiment in which larvae were reared in loose soil on grass roots, the mortality rate was seen to increase with the size and activity of the larvae, and also with the larval density.

This paper deals mainly with species of Tanytarsus (CHIRONOMIDAE) at Khartoum, particularly the very common T. lewisi Freeman. These midges are a serious pest there, usually between November and April, causing great annoyance by swarming in vast numbers around lights during the first few hours after sunset and thus interfering with work and pleasure in the riverain area. They are probably responsible for a considerable amount of asthma and other conditions due to allergy. Little information is available about the biology of CHIEONOMIDAE in Africa, so reference is made to the Palaearctic T. mancus Walker, to which T. lewisi is closely related. Studies of Chironomids from the health point of view elsewhere have little relation to the Khartoum problem, but work on Chaoborus (CULICIDAE) is of interest.

The conditions under which these midges occur at Khartoum and the methods of study are described.

At least 26 species of CHIRONOMIDAE, including four of Tanytarsus, occur at Khartoum. The respiratory organs of some pupae are figured, and a key, based on the characters of these organs, is given for some of the species.

Observations on the biology of all stages are recorded, particularly on the vertical movements and drifting of larvae and pupae and the time of emergence. Many larvae and pupae drift downstream at night, and T. lewisi emerges mainly in the early morning.

Some exploratory field trials of larvicides were carried out. The results were inconclusive, and the difficulty of assessing them is pointed out. Thorough control by anti-larval measures would be extremely difficult owing to the large size of the river and the drift of pupae from upstream. It is believed that it might be possible but prohibitively expensive, and would have to be repeated annually, perhaps throughout the midge season. Various protective measures are discussed. It is considered that riverside dwellers who can do so should move inland, and that a barrier of trees parallel to the river would protect houses away from the river front. People who must be near the river in the evening can achieve considerable protection by clearing some vegetation, fogging with insecticide, or using air-cleaning or air-conditioning equipment.

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.

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).

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.

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.

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.