1. The standards adopted by the author for a test insect suitable for the laboratory testing of insecticides are given.

2. The inadvisability of using insects collected in the field, or insects that do not breed naturally throughout the year, is illustrated.

3. The results of a search amongst stored-product insects, involving the testing of 27 different species, are given.

4. Ahasverus advena, Oryzaephilus surinamensis and Oryzaephilus mercator have been found to be suitable laboratory test insects.

Reactions to Temperature

1. The reactions of Culex fatigans to temperature were studied by means of a new type of temperature gradient apparatus based on the same principle as the humidity alternative chamber.

2. Females at different stages were exposed to a range of 5°C. at different parts of the temperature scale, and it was found that the sensitivity was very much greater at high temperatures than at low ones.

3. The most striking feature of behaviour at all stages was the strong avoidance of high temperatures. This was strongest in the hungry females, less strong in the blood-fed females and those with mature ovaries, and least strong in the newly emerged females.

4. Newly emerged females showed avoidance of high temperature below 30°C., but not below 25°C. They also showed a weak avoidance of low temperature. At 29°C. they were sensitive to a difference of 1°C. or a gradient of 0·05°C. per cm.

5. Hungry females showed a strong avoidance of high temperature below 25°C., the reaction still taking place below 15°C. There was no avoidance of low temperatures.

6. Blood-fed females and those with mature ovaries showed a strong avoidance of high temperatures below 25°C., but below 20°C. they were unaffected by temperature differences. Blood-fed females were sensitive to a difference of 1°C. or a gradient of 0·05°C. per cm. at 23°C.

7. Except in the case of newly emerged females there was quite a close relation between the reactions to temperature and the effects of temperature.

8. Reasons are given for regarding the temperature reactions of Culex as of first importance in determining the behaviour of the mosquitoes when seeking a resting place.

Reactions to Humidity

9. The reactions of Culex fatigans to humidity were studied by means of the alternative chamber, in a dark constant temperature room at 25°C.

10. At all stages the strongest humidity reaction was an avoidance of high humidities above 95 per cent. R.H.

11. This reaction was strongest in the blood-fed females and those with mature ovaries, less strong in the newly emerged females, and weakest in the hungry females.

12. The avoidance of high humidity was strongest when there was a difference of 20 per cent. R.H., such as a 78–98 per cent. R.H. gradient. Near saturation point all stages except hungry females were sensitive to a difference of 1 per cent. R.H. or a gradient of ·05 per cent. R.H. per cm. Hungry females at this point were not sensitive to a difference of less than 3 per cent. R.H.

13. All stages showed a slight but regular avoidance of low humidities, provided a sufficiently large humidity range, not less than 40 per cent. R.H., was present.

14. Hungry females, despite the onset of mortality due to desiccation, showed no sharp avoidance of low humidities which were rapidly fatal to them.

15. Between 30 and 85 per cent. R.H. all stages were unaffected by humidity differences of as much as 40 per cent. R.H.

16. The avoidance of high humidities was equally strong in blood-fed females at 20, 25, and 30°C. At 35°C., greatly increased activity eliminated the reaction.

17. The reaction was much less intense in daylight and disappeared altogether after sundown.

18. Reasons are given for considering that the measure of humidity which determines the behaviour of the mosquito is relative humidity and not saturation deficiency, even though the latter is the important one in the water relations of insects.

The family of the Eulophidae, which is probably the largest family of the Chalcidoidea, is still very little known, both systematically and biologically. Being small, they are often bred in large numbers from a single host and are thus of great economic importance, but not always useful, as many species are hyperparasites. The study of the African Eulophidae is still at its beginning, since only about 60 species are known, two-thirds of which have been described by Waterston and Silvestri. The Imperial Institute of Entomology has received and is receiving many species which still remain unnamed. Most of them belong to large genera, like Euplectrus, Pleurotropis, or Tetrastichus, which should be studied monographically. The six species described below have been chosen partly for their possible economic importance, partly because they are represented by series of males and females.

Research on the control of maggot-fly on sheep has in the past been seriously handicapped by the uncertainty of natural incidence of strike ; many experiments have been rendered invalid by the failure of the controls to react, the absence of controls, or by reason of the fact that the incidence of strike was so low as to make differences between comparative groups of no significance. For these reasons much of the published evidence does not bear critical examination.

There are now available, however, critical methods for the estimation of the protective value of dips and sprays, and it is essential, if further progress in maggot-fly control is to be made, that use be made of these methods for the accurate assessment of the larvicidal and repellent properties of experimental dressings, and for the duration of effect of these properties. A continuation of the present tendency to general statements that such and such substances were found to protect sheep for so long, without specification of what precisely the sheep were being protected against, and especially when unaccompanied by detailed protocols which will.allow the reader to exercise an independent judgment of the reliability of the results, will only lead to further discordance in a subject already suffering from a lack of uniformity in the standards of different workers, and the absence, even, of any precise definition of much of the technical jargon associated with it.

In the first part of this paper the nature and potentialities of the three possible functions of a maggot-fly dip or spray have been outlined, and the appropriate terms defined. It has been pointed out that field tests, for which it is difficult and sometimes impossible to furnish logically acceptable control data, are unreliable and may be definitely misleading ; at best they still leave the investigator uncertain as to which function of the dressing is responsible for the protection conferred, and consequently handicapped in his efforts to improve still further the protective value of the preparation under test.

In dealing with the maggot-fly problem, two principal lines of attack are possible ; the fly may be prevented from laying its eggs, or alternatively, the fleece may be so impregnated with toxic chemicals that the eggs, or any larvae which succeed in hatching from these, are killed. If a completely reliable repellent were available, no larvicide would be necessary ; conversely, if a thoroughly effective larvicide were available, a repellent would be not only unnecessary but also undesirable, for the more eggs which the flies could be induced to lay on sheep the better.

A third possible line of attack is the use of an antiseptic, which neutralises the bacterial activity in the fleece, and so ends the attraction of the sheep for the gravid female fly. Since, however, such neutralisation is so easily overcome by accidental fouling of the fleece, scouring or other cause, it is obviously unsafe to rely on this negative virtue alone for immunity from attack. The overcoming of the antiseptic property is the chief reason why carbolic dips, which rely on their antiseptic value, tend to have no effect, or even to have a harmful effect, after the dipping solution begins to get fouled by urine and faecal matter. With larvicidal dips, this fouling is of much less consequence, for the active protection conferred by the toxic chemicals prevents the blows which result from any such fortuitous “ attractivation ” from developing to strike.

With regard to the two principal lines of attack mentioned above, it may be stated here that prolonged and thorough tests have failed so far to reveal any substance possessing a reliable repellent action, which remains completely reliable for more than a few days. In all the commonly used repellents tested, the protection was found to be uncertain and seldom of a high degree, It appears, therefore, that we have yet to find the ideal repellent, and until such time it is obviously safer to rely on larvicidal protection.

It is equally obvious that, to ensure thorough penetration of the larvicide, it must be applied by actual immersion of the sheep. Spraying, though the ideal method for applying a repellent, cannot be regarded as suitable in the case of a larvicide, since it coats only the outer part of the wool staple with the spray fluid, and does not thoroughly saturate the fleece down to the skin surface.

With regard to the experimental evidence given in detail in the present paper, the results may be held to suggest the following conclusions:—

1. Carbolic dips neither repel the adult fly nor prevent larvae from establishing active strike on the skin.

2. Cresylic acid, incorporated in a mineral oil base, is not effective as a spray or as a dip in protecting susceptible sheep or preventing development of strike from blow.

3. Arsenic remains in the fleece, and continues to exercise a protective effect against development of strike for some weeks after application. This protection may be only partial (Table III) or almost complete (Table II, IV and VII) ; under winter conditions it lasts for about four weeks, and in the case of one form of soluble arsenic at least, it has been shown to be only slightly affected by heavy rain.

The following paper deals with collections of sandflies made by Professor P. A. Buxton in Nigeria, and by the late Professor J. G. Thomson in Nyasaland, and collections sent by Sir Guy Marshall, Director of the Imperial Institute of Entomology, and by Dr. F. W. Edwards of the British Museum (Nat. Hist.), for identification.

Die Wanderheuschrecke (Locusta migratoria, L.), in früheren Jahren in Rumänian einst eine der gefürchtetsten Plagen, ist heute meist auf das Donaudelta beschränkt ; sehr selten sind Jahre, wo der Massenwechsel in dem Masse sich gestaltet, dass sie das Gebiet auf weitere Strecken verlässt.

During the latter half of 1936 a search was undertaken for predators and parasites that might be of use against certain Coccidae which are causing considerable damage to the coconut crop in Seychelles.

During recent years in Sweden much time and work has been devoted to the devising of accurate and withal time-saving methods of estimating the number of bark-beetles breeding in a trunk as well as the total number of bark-beetles per hectare in a given instance. The results achieved by the methods finally adopted seem to us so satisfactory that we venture to think that the methods in question may be used to advantage even in other countries, when similar problems arise.

Protostrophus dianthi, sp. n.

♀. Black, with dense grey and pale brown scaling ; head brown with a grey stripe adjoining the eyes ; prothorax with a broad indefinite median brown stripe, the lateral areas grey with brown spots which sometimes form two narrow irregular stripes, the pleurae brown above and grey below ; elytra mottled with pale brown and grey, intervals 2, 5 and 6 usually with dark brown patches, the suture pale fulvous.

The Nigerian Agricultural Department is endeavouring to find cattle with a sufficiently high degree of natural resistance to trypanosomiasis to enable them to be utilised for mixed farming in the Ilorin Province and elsewhere in the Middle Belt of Nigeria. In April 1935, a herd of West African Shorthorn cattle was obtained from the Gold Coast and these and other animals, purchased in Nigeria, were established at a central stock farm at Ilorin.