The biology of Pullus impexus (Muls.), a Coccinellid beetle predacious on Adelges piceae (Ratz.) in Switzerland, Germany and France, was studied during 1950–1952. The present work is a part of the research on the complex problem of factors in the control of the Balsam Woolly Aphid in Canada.

The morphology of both the larva and the adult has been studied. Some information has been provided on the probable distribution of the species.

P. impexus has only one generation a year. The eggs are deposited during the late summer or early autumn on infested trees and the larvae hatch in April. The larvae develop and adults appear in May. The adults of the new generation are to be found in June together with adults of the old generation. In the biology, particular attention has been directed to the diet of the insect in each of its stages, in order to establish the value of the species from the standpoint of biological control.

Two new species of Hymenopterous parasites were found in Switzerland and in Germany, Scymnophagus mesnili Ferr., a parasite of pupae, and Centistes scymni Ferr., a parasite of the imagines. The life history of these species has been briefly studied. A cephaline gregarine species was noted in the mesenteron of adults of P. impexus and a nematode in the abdominal cavity of a female. The two Hymenopterous species provide an important limiting factor in the increase of the population of P. impexus.

Aneityum is the only Pacific island south of Latitude 20°S. from which Anophelines and autochthonous malaria have yet been reported. Both Plasmodium vivax and P. malariae were found there, the former species only being detected in the blood of children who had visited the nearby island of Tanna and the latter in that of children who had never left Aneityum. Autochthonous quartan malaria has not previously been reported from the New Hebrides. In the absence of any other Anophelines from this group, it must be assumed that Anopheles farauti Laveran is the vector of P. malariae at Aneityum.

The mosquito fauna of New Caledonia and the Belep Islands is discussed, together with some features of the larval morphology of Culex (Culex) pipiens fatigans Wied., C. (C.) annulirostris Skuse and C. (Neoculex) pseudomelanoconia Theo. Culex (C.) bitaeniorhynchus Giles, herein recorded from New Caledonia for the first time, is probably a post-war introduction into the Noumea area from Australia. Culex (Lophoceratomyia) fraudatrix Theo., recorded from Art Island (Belep group), has not previously been known from the New Caledonian area. From the mosquito and blood-smear survey in the Belep Islands, it is concluded that these islands, like New Caledonia, are as yet free from Anopheles and malaria.

Five experiments in the use of insecticides against Calandra oryzae (L.) in stored maize are described. The results with statistical analysis and deductions are given. The insecticides used were BHC, DDT, pyrethrum, pyrethrin-piperonyl butoxide mixtures; the diluting dusts used were a local diatomite, a local bentonitic clay, and a local soapstone.

Among the chief conclusions are the following:—

The insect damage in conditioned grain did not reach, throughout an eight-month period, the high level which it did in unconditioned grain, the conditioning process alone therefore is a valuable treatment for insect control.

Bentonite alone is not a protectant and its addition to grain may on the contrary provide a more favourable environment for Calandra.

A Kenya soapstone (from Kisii) is not an effective protectant but had some effect in reducing Calandra populations over the period when an initial increase was occurring in control bags.

Kenya diatomite is a protectant. It reduces the percentage of grain damaged, but when used in bagged grain this is not proved to be due solely to intrinsic toxicity, but may in fact be due chiefly to the slippery nature of the material inhibiting insect distribution through the bulk of grain.

Gamma BHC at 1 p.p.m. is completely effective for 16 months.

Gamma BHC at 0.5 p.p.m. has some protectant effect but is not fully effective.

DDT at 7 p.p.m. has not a protectant effect.

A method is described for rearing Drosophila melanogaster Mg., which provides a high and consistent yield of adult flies, of uniform age and size, for insecticide studies.

A microburette made from glass capillary tubing is mounted on the mechanical stage of a microscope and filled with insecticide solution to a point at which the meniscus is in the field of the microscope. The magnified images of the meniscus and a calibrated micrometer scale in the eyepiece are projected on to a small screen mounted close to the tip of the microburette so that the scale and the insect being dosed can be seen simultaneously. This feature renders the apparatus particularly suitable for topical application work in which accurate positioning of the dose on the insect is required. When an insect, held in a suction device described, is applied to the tip of the burette, the solution flows out unaided, and stops immediately the insect is removed. With the microburette described, doses from 0.005 to 0.035 μl. can be dispensed to within ±0.00035 μl. The apparatus can be made to cover several other dosage ranges, either lower or higher, by simple modifications which are discussed.

DDT in odourless distillate was topically applied to individual males and females of the Rothamated wild type of Drosophila melanogaster Mg. The lines for the regression of mortality in probits on log. dosage of DDT for males and females, five days old, were parallel, and males were 1·86 times as susceptible as females. Susceptibility was high in young flies, but rapidly decreased with age, to a minimum at about five days, thereafter increasing rapidly in males and not significantly in females. The need for sexing and standardising age in flies used for toxicological investigations was thus demonstrated.

Respiration rate in untreated flies was measured by a modified Barcroft method. In males it increased with age up to five days, and then decreased; in females it increased with age up to nine days. Variations with age in respiration rate and susceptibility to DDT were negatively correlated.

Using mainly the overwintering prepupae of a “ slug caterpiller ”, Cnidocampa flavescens (Walk.), the mechanism for the frost-resistance in insects was investigated.

Though the freezing point of the blood shows the value of about −2°C. the prepupae are very readily supercooled. When cooled below −20°C., however, the insect body suddenly congeals hard. Insects frozen thus, even for a long period of 100 days, usually withstand the solidification of their bodies without any harmful effect upon either the further development or upon the next generation.

Judging from the shape of the freezing curves of the prepupae and the freezing processes of the blood and isolated tissues, it is inferred that the most probable freezing process of the caterpillar is as follows. At first, the blood freezes rapidly, and consequently the grade of supercooling of the tissue cells is very much lessened by the latent heat of fusion of ice. Extra-cellular freezing of the tissue cells then takes place, in which case the properties of the blood as well as some property of the plasmic surface layer of the cells may play an important role in the prevention of the transmission of freezing into the cell. With the advance of the blood freezing, the tissue cells undergo dehydration and contraction; neverthless, they usually withstand such a condition for a long period, provided that the freezing temperature is not too low. Consequently, the so-called anabiotic state of a frozen insect does not necessarily mean the destruction of the cell structure.

Laemophloeus minutus (Ol.) has been reared on six food materials of a type with which the genus, Laemophloeus, is commonly associated in the field. Consideration of the length of egg to adult development, together with the mortality, recorded from each medium indicates that Manitoba wheat and whole-meal flour are equally favourable for the development of the species, followed in order of precedence by Plate maize, English wheat and, finally, National (85 per cent. extraction) and Canadian (70–75 per cent. extraction) flour which proved equally unfavourable.

The stage of the life-history at which mortality mainly occurred varied with the diet. The high death-rate on English wheat was caused by the inability of newly hatched larvae to enter grains undamaged in the germ region. Mortality on National and Canadian flour occurred chiefly in the fourth instar.

There were indications of cannibalism in both larval and adult stages, at any rate when the diet was unfavourable.

The germ of wheat was attacked in preference to any other part of the grain. Maize germ was also consumed but whether it was preferred to the same extent as that of wheat was not established.

Pupation was mainly, but not exclusively, intergranular in wheat. Normal cocoons were formed in National and Canadian flours but some larvae pupated in loose webbing or in flour free from webbing and freshly emerged adults were observed in unwebbed National and Canadian flour.

Experiment showed that all developmental stages of Lacemophloeus minutus (Ol.) can survive exposure to a temperature of + 2°C. for a limited period which varies with the instar.

The egg was more susceptible to such exposure than any other stage, followed by the first, second and third larval instars and the adult, which did not differ significantly from each other, and then by the fourth-instar larva and pupa which can also be grouped together.

The adult male proved 1·21 times more susceptible than the female to the effects of exposure.

Atmospheric humidity did not influence the mortality of eggs or adults. Previous starvation did not affect the mortality of adults subsequently exposed to + 2°C.

The behaviour of Anopheles gambiae Giles and A. funestus Giles was studied under natural conditions in a lowland area of Tanganyika.

Studies on the outside resting population were carried out by direct searching for natural resting sites, and by the use of artificial box shelters partly buried in the ground in shaded localities. Catches in these give a valid sample when set up at some distance from houses.

Fed and gravid females comprised 67 per cent. of the outside resting gambiae population, the latter group being between 12 and 4·5 times as numerous as the former. Rather less than half the funestus females caught were unfed, the remainder of the population being mainly composed of gravid females.

Precipitin tests on the small numbers of fed females caught outside were nearly all positive for man.

The identification of gravid funestus females was confirmed by periodic examination of the eggs.

Entry of females into outside shelters did not occur solely in the period around sunrise. An appreciable number of funestus females did not enter before 07.00 hours and this was particularly so in shaded shelters.

The building of a hut in the vicinity of a box shelter caused a drastic reduction in the numbers of mosquitos resting in the latter.

Outside biting activity in these two species is of negligible importance as a source of females resting outside.

Observations on the behaviour of Anopheles gambiae Giles and A. funestus Giles in experimental huts and ordinary African houses were carried out in a low-lying area of Tanganyika. Special attention was paid to the exodus of females at different stages of the gonotrophic cycle and to the composition in terms of ovarian development of the house resting population.

About 5 per cent. of the biting population of gambiae and the same number of funestus were shown by the use of window traps to be leaving experimental huts after feeding.

Forty three per cent. of half-gravid gambiae left an experimental hut at dusk, 12–24 hours after entering for a blood meal, whereas only 3 per cent. of funestus left under the same conditions.

Daytime spray catches of gravid gambiae and funestus made in ordinary African houses during the hot season were about 50 per cent. and 30 per cent. lower, respectively, than the corresponding numbers of recently fed specimens. A. funestus therefore makes rather less use of outside shelters than gambiae during the hot months.

In the cool season about 50 per cent. of half-gravid and gravid funestus were absent from house catches.

No mortality could be detected amongst funestus females resting under natural conditions for 24 hours in an experimental hut.

Re-entry of gravid funestus into unoccupied and open types of inhabited houses occurs at dawn.

Sixteen of the numerous described species of Carpophilus Stephens have been found associated with stored products in different parts of the world, and of these, several species are continually distributed by international trade and have become established in many countries.

A key to most of these species is given, several of the species are redescribed and new taxonomic characters, mainly associated with the genitalia, are introduced and figured.

A Table is given summarising recent importations of Carpophilus species into Britain, detailing the commodities on which the insects have been found, their places of origin and the number of individual records.

In the course of general studies on control of Culex pipiens fatigans Wied. in British Guiana, the indigenous shrub Ryania speciosa, proven to possess insecticidal activity against certain agricultural pests, was investigated.

Aqueous extracts of the dried stem were shown to possess toxic properties against all larval stages of C. pipiens fatigans under clean laboratory conditions. Under conditions simulating a water-logged pit latrine, however, toxicity was greatly reduced by adsorption of the active agent ryanodine, rendering the crude stem relatively ineffective after 16 days. Because of the great bulk of unprocessed material required for even this limited result in pit latrines—which constitute an important local problem—Ryania was not considered of practical value in C. pipiens fatigans control.

Aqueous and alcoholic extracts of Ryania speciosa had no contact insecticidal properties against adults of this species.