Cacoecia histrionana Froel. a European relative of the North American spruce budworm, Choristoneura fumiferana Clem., was found in several localities on the north-eastern frontier of Bavaria in 1949, but was not abundant anywhere.

Details are given of its biology based upon observations made during large-scale collecting in the summer of 1949, which yielded approximately 2,100 larvae of C. histrionana.

An important characteristic of the species is the great variation in the stages of larval development present at any given time, which is apparently caused chiefly by the absence of diapause as a synchronising factor.

Approximately 4°C. was found to be the lower temperature limit for movement and feeding of larvae ready for overwintering.

Three samples of larvae taken in favourable localities showed that 0-15 to 0-70 larvae were present per metre length of spruce forest edge from ground level to a height of 2 metres. An estimate of the minimum population is made for a limited and well searched area.

From 1803 C. histrionana larvae collected in the field, 15 species of primary parasites and four of hyperparasites were bred. Combining the result of three samples taken at different times the minimum reduction of the population after hibernation is calculated to be 66-8 per cent., the parasitism of pupae at least 13-5 per cent. Egg parasitism occurred.

Nine of the 20 parasites, known hitherto from C. histrionana, have been bred from other hosts of the same animal community.

The most important larval parasite was Meteorus ruficeps Nees which completes 2-3 generations in one generation of C. histrionana. A proportion of the population also overwinters in other Microlepidoptera, concentrating on C. histrionana in summer. Details of its life-history are given.

Occasionally some larvae were found that had probably died from disease but disease, as a mortality factor, was of little consequence in the observation area in 1949.

Mortality caused by parasites proved to be very important in affecting changes in the population density. This result does not agree with Eidmann's theory that the scarcity of C. histrionana is due to climatic control.

The effect of piperonyl butoxide (PB) on the toxicities of allethrin, DDT, and BHC in a heavy oil base to Tribolium castaneum beetles has been tested. PB synergised allethrin and BHC both in films and direct sprays. It antagonized DDT in films, but left the toxicity of DDT unchanged in direct sprays.

The effect of PB on the joint toxicity of BHC and pyrethrins to T. castaneum was also investigated, applying the materials as direct sprays. The data were not so conclusive as had been hoped, but they indicated strongly that in a mixture containing all three materials the PB synergised each insecticide as though the other were absent, i. e., it synergised both simultaneously.

The experimental findings of the present paper are examined in conjunction with the findings of Hewlett and Plackett (1950). It is shown that there is an underlying similarity between the film and direct spray results for the joint toxicities to T. castaneum of pyrethrins, DDT, BHC, and PB, taken in pairs.

Further studies were made of G. medicorum and G. fusca using the resting-haunt technique.

During 5½ collecting days, 200 G. medicorum and G. fusca were taken by the resting-haunt technique ; over this period, only one fly was taken by the normal, human bait technique.

Out of 119 G. medicorum 45 per cent, were females, and out of 73 G. fusca, 44 per cent, were females ; the resting-haunt technique yields a good cross-section of the tsetse population.

Out of 15 recently gorged G. medicorum and eight G. fusca examined, all contained mammalian blood. Gorged flies were very numerous, so that it should be possible to ascertain the wild hosts by the precipitin test.

From the evidence available, it is believed that at the end of the rains both G. medicorum and G. fusca feed only during the twilight hours, or when the forest is fully illuminated by the moon.

Collections of Cactophagus spinolae (Gylh.) were made in Mexico in 1946, 1947, and 1948 to supplement the biological control of prickly pear (Opuntia spp.) in South Africa. During these three years, 862, 1,396, and 15,584 adults, respectively, were dispatched to South Africa. The weevils were sent by air express in specially designed containers, and arrived in excellent condition.

This paper includes information on the distribution, life history and food preferences of C. spinolae. The need is stressed for anticipating the effects of transit conditions upon living insect material transported by aircraft.

An arsenic-resistant tick was first noticed in the East London district of South Africa in 1938–39. It was a strain of the one host blue tick, B. decoloratus. BHC was very toxic to the tick, as 50 p.p.m. of the gamma isomer killed adult females in in vitro experiments. Field results in 1946–47 were equally convincing. Weekly dippings in BHC washes containing 50 p.p.m. gamma isomer brought the arsenicresistant tick under control.

In March 1948, BHC was found to be ineffective against blue ticks at “Burnside”, “Mistley” and “Gulu”, farms in the East London district. Later, ticks at “Tharfield” and “Elmhirst” in the Bathurst area survived regular weekly dippings in BHC preparations. In vitro experiments showed that adult female blue ticks taken from these localities could withstand high concentrations of gamma BHC, while females of the same species from other areas were readily killed. Not even 1,000 p.p.m. would give 100 per cent. control of ticks from resistant areas, and different sources of gamma BHC were equally ineffective. Laboratory experiments further indicated that the ticks were still arsenic-resistant. Indeed arsenic resistance appears to be associated with BHC resistance, as no BHC-resistant tick has been found that is not arsenic-resistant. The chlorinated cyclic hydrocarbons toxaphene and chlordane were ineffective against BHC-resistant ticks, but controlled BHC-sensitive ticks in the laboratory. DDT gave moderate in vitro results against both resistant and sensitive ticks.

Laboratory and field experiments were carried out to study the toxicity of 3:5 dinitro-ortho-cresol and its sodium salt to the honey bee.

The acid DNOC was shown to be a rapidly acting poison under a wide variety of conditions and its toxicity was not greatly affected by differences in temperature or humidity during or after treatment.

Although both the acid and salt were equally toxic as stomach poisons, considerable differences were observed between the two substances as aqueous sprays and dry films. The toxicity of the sodium salt as an aqueous spray was considerably influenced by the humidity of the environment after spraying; the higher the humidity the greater the kill.

The sodium salt was apparently non-toxic as a dry film and increasing the humidity of the environment had no effect until the saturation point was reached and the salt went into solution. At this point the salt was almost as rapid in action as the acid. The type of surface on which the film was deposited was also shown to affect the toxicity.

Experiments were carried out on the penetration of the two substances through beeswax and these confirmed that whilst the acid could penetrate the beeswax in all forms tested the salt would only penetrate in aqueous solution.

A development of grasshoppers to minor plague proportions over a limited area of the Rift Valley near Lake Elmenteita occurred in 1950. The two chief species concerned were Gastrimargus brevipes Sj. and Caloptenopsis glaucopsis meruensis Sj. but many other genera and species were present and are listed. The distribution of rain with appreciable falls followed several times by dry spells may have been a factor contributing to the increase. An unusual increase of the Coccinellid, Epilachna hirta (Thnb.) also occurred in the area a month or two before.

A study of the immature stages of the Anthomyiid flies, Delia cilicrura, D. trichodactyla, Erioischia brassicae, E. floralis and Pegohylemyia fugax, associated with injury to cruciferous crops, has shown that the several species can be distinguished. The egg stage can be identified by the sculpturing of the chorion, except in the case of the closely related species E. brassicae and E. floralis where the sculpturing is similar but there is a considerable difference in size.

The larvae can be distinguished by differences in the shape and character of the head and in its relation to the prothorax, and in the form of the mouth-parts in the three instars. The number of finger-like processes of the anterior spiracles and the number and arrangement of the tubercles of the eighth abdominal segment also contribute to the identification of the larvae.

The physical state of deposits from various formulations of insecticides applied to different materials is considered in relation to the availability of the insecticide to insects making contact with the surface of the treated material.

Applications of oil solutions of insecticides to absorptive material result in absorption of the solution, and the insecticide is thereby rendered ineffective. On a nonabsorptive surface, oil solutions are the most efficient formulations, but only so long as the deposit remains wholly or partly liquid; if evaporation of the solvent gives a dry crystalline residue, this is much less efficient than the original solution.

On some fibrous absorptive surfaces, a solution of DDT in oil remains in a supersaturated condition in and around the fibres. If crystallisation is stimulated by mechanical means, the resulting crystals project from the treated surface and it is suggested that, in these circumstances, crystals are more readily available to insects than the oil solution from which they were derived.

DDT on compressed wall board shows the induced crystallisation to a greater degree than other insecticides. It is concluded, therefore, that wall board and similar surfaces should not be used in comparing the potencies of chlorinatedhydrocarbon insecticides applied as oil solutions, as DDT would be more available than others. Some factors that affect the degree of induced crystallisation are mentioned.

The process of build-up of reserve substances in Locusta migratoria migratorioides (R. & F.) is very closely correlated with the feeding activity of the insect. Locusts attain their maximum body weight in the initial period before maturation. In the females there is one minor build-up period after each laying.

As measured by the weight of faeces produced, the gregaria female consumes more food than the solitaria during development. It also has a lower rate of increase in body weight, maturation and oviposition.

Locusts start to build up fat soon after the final ecdysis. The fat content reaches its maximum in the early part of adult life, and then begins to decline in both sexes of both phases.

By far the greater part of the fat reserve thus built up in the gregaria female is used up before oviposition, and only a small amount goes to the making of the first egg-pod. The fat of the subsequent egg-pods (of both phases) is derived from the fat built up each time after a new egg-pod is laid.

The solitaria females may mature their eggs at various stages in the development of the fat body. Those which have a longer pre-maturation period have a higher fat content.

In Nigeria, shelled groundnuts are stored in sacks in covered warehouses and as pyramids in the open air. At the beginning of storage the nuts comprise approximately equal quantities of whole, split and broken nuts of a moisture content of 3·4 per cent. The sacks are exposed to direct hot sun whilst stacking.

The mean monthly maximum shade temperature in Kano ranges from 101°F. in April to 85°F. in January and August and the mean monthly minimum from 75°F. in May to 56°F. in January. Monthly maximum relative humidities range from 100 per cent, in August and September to 45 per cent, in February, and the monthly minimum from 71 per cent, in August to 12 per cent, in February. The range of mean relative humidity is 81 per cent, in August and 18 per cent, in February. Rains fall between April and September, 70 per cent, falling in July and August. Heavy falls are recorded on about 25 days.

Inside warehouses, the maximum monthly temperatures are 102°F. in May and 79°F. in January and February, and minimum temperatures are 81°F. in June, and 58°F. in February. In August the mean relative humidity range is 93 per cent, to 70 per cent. In December it is 34 per cent. to 20 per cent.

Just under the roof of a warehouse and on the surface of pyramids the diurnal range is very large.

The problem of insect infestation of stored export food commodities in southern Nigeria is discussed, and a list of insects is given. At the ports there is considerable cross-infestation between commodities produced in northern and southern Nigeria awaiting shipment.

Old sacks used for the storage and transit of groundnuts are responsible for the spread of insects to palm kernel and cocoa marketing centres in the south. After bulk shipments of a portion of the groundnut crop, sacks are repaired and distributed for the shipment of palm kernels and some of them may be used by fanners and brokers as service bags for the marketing of cocoa and local food commodities. The importance of disinfestation before distribution is realised, and a small fumigation plant is in operation at port.

Ephestia cautella and Lasioderma serricorne are the major pests of stored cocoa beans. Both originate in farmers' and brokers' stores which are rarely cleaned, and in which small parcels of low-grade beans may be retained for mixing with a following crop to conform with an exportable grade. Ephestia cautella also infests palm kernels, and the early abundance of adult moths in cocoa stores up country during the marketing season is considered to be largely due to the storage of palm kernels in the vicinity. The development of Ephestia larvae can be completed on the outside of cocoa beans, only germinated or damaged beans being penetrated.

The biology of N. hololeucus, T. globulus, G. psylloides, S. squamosum and E. hilleri has been studied to estimate their potentialities as pests of stored products.

They are widely distributed and feed on a very wide range of foodstuffs of both plant and animal origin.

Adult life is usually longer than the development period. Oviposition extends over most of the adult life. In warehouses all stages of development are present together.

At 70 per cent. R.H. the developmental period (egg laid to emergence of adult from its cocoon) comprises: 12 to 21 per cent. as the egg stage, 52 to 70 per cent. as larva, 12 to 16 per cent. as pupa and 6 to 19 per centg. as adult in cocoon.

The mean lengths of the various developmental stages, including the larval instars, have been found under several sets of physical conditions.

The properties of two DDT suspensions of a new type, “Supona”-D and “Supona”-DB are described. These suspensions contain about 50 per cent. DDT or 39 per cent. DDT+ 13 per cent. technical BHC respectively in their concentrated forms, the active material being suspended in a complex colloidal oil-water system.

Experiments were carried out with “Supona”-D and a DDT emulsion containing about 30 per cent. DDT dissolved in a mineral oil phase for the control of Glossina palpalis. Both products were applied in dilutions containing 5 per cent. DDT.

Laboratory experiments with leaves of Camellia thea and Begonia sp. showed that the initial toxicity and stability in tropical sunlight of residues of “Supona”-D were somewhat less than those of the DDT emulsion. The resistance to rain, however, was better with residues of “Supona”-D.

A method is described for the extraction of arthropods from soil.

Eleven soil samples from pastures in the neighbourhood of Moshi, Tanganyika, and at Kawanda, Uganda, yielded collections representing a population of 54,565 arthropods per sq. metre in the top 6 ins. of soil or, if three samples are adjusted in conformity with biological indications, of 38,417 per sq. metre.

Nine soil samples from coffee and cassava plantations and from fallow ground gave collections representing a population of 24,423 arthropods per sq. metre in the top 12 ins. (in some cases 8 ins.) of soil.

Twenty-five soil samples from a pasture near Cambridge, examined in a strictly comparable manner, gave collections representing a population of 90,238 arthropods per sq. metre in the top 6 ins. of soil.

It appears that the arthropod population in the uppermost 6 ins. of East African pasture soil is much smaller than, and only about half as large as, that in an English pasture.

The causes and consequences of the smaller arthropod population of tropical soil are briefly discussed, and a connection is suggested between the meagre arthropod (and earthworm) population and the large amount of ligneolis material found in the soil samples examined, This connection may also bear on the paucity of humus in some tropical soils.

Sir Rickard Christophers (1947) working at 25°C. and a relative humidity of 80–90 per cent. found female Aëdes aegypti to be attracted by a warm dry surface at 40°C., and to be unaffected by a moist surface at room temperature. The writer (1948), working at 28°C. and 50–70 per cent. R.H. (usually near 50 per cent.) found the opposite: a warm dry surface at temperatures from 36°C. to 40°C. had no effect, while a moist surface at room temperature exerted a quite definite attraction. The purpose of the present experiments was to test the hypothesis that the difference between the results obtained in these two investigations was due to the difference in the ambient temperature and humidity.

Repetition of the relevant experiments at 25°C, 85–90 per cent. R.H., and 28°C, 50–55 per cent. R.H., gave results indicating that temperature and humidity difference operating at the time of the experiment could account for part but not all of the discrepancy. There are indications that the remainder may have been a result of the conditioning effect of temperature and humidity differences operating on the insect prior to the experiment.

The results emphasise the need for a full description of the climatic conditions under which behaviour work of the type discussed is performed.