Although it may be convenient to distinguish them, hibernation, aestivation, and diapause are in reality different manifestations of the same phenomenon which we may call diapause. The symptoms of this condition are a marked depression of metabolism and quiescence; and the remote causes as suggested by observation are cold, heat, drought and (or) certain nutritional peculiarities such as richness or dryness of food. These factors may act singly or in combination, with different factors dominant in different cases.

Twenty-three species of Metaphycus from Africa are recognized in this paper, and of these, seventeen are described as new. The holotypes and allotypes of all new species are to be deposited in the British Museum and paratypes in the United States National Museum.

1. Eight Ichneumonoidea, fourteen Chalcidoidea and six Proctotrupoidea are recorded as parasites of willow insects.

2. The majority of records are of parasites bred from insects inhabiting the wood of the cricket bat willow, Salix alba var. caerulea, Smith, the more important being Torymus pulchellus, Thoms., Tridymus salicis, Nees, Eupelmus urozonus, Dalm., Microterys clavellatus, Dalm., Tetrastichus roesellae, DeG., Tetrastichus inunctus, Nees, Tetrastichus flavovarius, Nees, Tetrastichus ? acuminatus, Ratz., and Platygaster sp.

3. Microterys clavellatus is recorded for the first time as a parasite of Cecidomyiidae.

4. Evidence is given for the separation of the gall-midges, Rhabdophaga sp. and R. saliciperda, Duf., as distinct species based both on structural differences and on a study of their parasites, for the three parasites found most commonly attacking Rhabdophaga sp. were never bred from R. saliciperda, and the most common species parasitizing R. saliciperda was never obtained from Rhabdophaga sp.

5. It is confirmed that Eurytoma salicis, Thoms., supplements its animal diet with vegetable food.

6. The rate of parasitism of Euura atra, Jur., by Eurytoma salicis is given as 19·8 per cent., and that of Rhabdophaga sp. by Platygaster sp. as 40·5 per cent.

7. Histograms are given of Rhabdophaga sp. and its parasites, Torymus pulchellus, Thoms., Tetrastichus roesellae, DeG., and Platygaster sp., the emergence of Platygaster sp. coinciding approximately with that of its host.

At least 30 specimens of each form of Macrosiphum rubiellum, Theobald, and Aphis idaei, van der Goot, were collected, mounted and their principal organs measured.

Correlations were calculated between different parts on the right side and the conclusion reached that the ratios of lengths of organs were unstable characteristics of the species examined. High correlations were obtained between the same part on different sides of the body.

The mean values and standard errors are tabulated and a method given for assigning limits of variation within a species. The standard errors obtained were of the order of 7 per cent. of the mean.

The asymmetry, kurtosis and skewness of the distributions were calculated to test the effect of possible non-normality on the foregoing work.

In a previous paper (Leeson 1937) it was shown that in East Africa there were variations in the wing markings of the type form of Anopheles funestus. It was further shown that larvae and pupae positively identified as typical A. funestus produced adults having these wing markings. Identification of the adults was confirmed by examination of pharyngeal armatures and male terminalia. The wing forms were then arranged in the following four groups:— Group 1: dark area at base of costa uninterrupted, 3rd vein with a pale interruption. Group 2: dark area at base of costa uninterrupted, 3rd vein entirely dark. Group 3: dark area at base of costa interrupted by one pale spot, 3rd vein with a pale interruption. Group 4: dark area at base of costa interrupted by one pale spot, 3rd vein entirely dark.

Through Dr. O. W. Richards, the Imperial Institute of Entomology has recently received for identification specimens of a Trichopria parasitic on two species of tsetse-flies. It appears to be new and, since it may play a part in the control of its hosts, is described below.

Edwards (Bull. Ent. Res., 1930, 21, p. 290) originally described this species from the Belgian Congo. Two further adults from Ndola, N. Rhodesia, were examined by Evans (Mosquitoes of the Ethiopian Region, II, Anophelini, 1938, p. 246) who noted that these differed from the type species in having the costa without a pale sector spot and the third vein with a large dark area at the apex. The present specimens (also from Ndola) show that these differences are not constant; in one of the two females there is a small sector spot present on one wing, the other wing and both wings in the second female have no sector spot, both females have a rather small dark area at the apex of the third vein. In two of the three males a sector spot is present on both wings, while in the third specimen this spot is absent from both wings. On the whole the wings may be said to be darker than those of typical walravensi from the Congo, and these Ndola specimens may be taken as representing a darker form but not worth subspecific rank. Associated with these five adults were four larval pelts and five pupal pelts obtained from isolated specimens. We therefore take this opportunity of describing the larva and pupa.

1. The removal of the thicket windbreak from around a residual forest island considerably alters its climate and intensifies the rigours of the dry season. The evaporation rate becomes much higher; appreciable increases are caused in the atmospheric diurnal temperature, but are more pronounced in the soil temperature. The island becomes slightly colder at night.

To be forewarned is to be forearmed and it is for this reason that the following information has been written concerning a gall midge which has recently been reported attacking apple blossom in Japan and another gall midge which attacks black currant flowers in Finland. Both prevent the formation of fruit. It is possible that either or both of these pests may appear in other countries.

Egg Parasites.—In the Eastern Transvaal, Swaziland and Natal the eggs of Heliothis armigera are parasitized by Trichogramma luteum, Gir., and Telenomus (Phanurus) ullyetti, Nixon. No other egg parasites have been encountered.

Representative samples of eggs were collected weekly or twice-weekly over a period of seven years and over wide areas from the various cultivated crops and colonies of wild food-plants which exemplify the annual chain of breeding sites of H. armigera. The collected eggs were incubated to determine the “active” fraction derived after withdrawal of the infertile portion and of eggs exposed for less than 24 hours to parasite action. Observed parasitism was computed against the “active” eggs and is regarded as an index of the parasitism in the field. Running indices of this nature are given graphically to indicate the annual incidence of egg parasitism in percentages, which may be viewed in relation to the incidence of bollworm as evinced by oviposition data in the figures given. Sustained high levels of parasitism are associated mainly with the more abundant egg populations on winter-irrigated vegetable crops grown between July and November.

It has been found that Telenomus occurs mainly in the period August to December, and Trichogramma in the period December to March–April. The high parasitism of the winter egg populations is due, therefore, almost solely to Telenomus.

Evidence is submitted that the levels of parasitism in certain crops are commonly much higher than in others. Explanations are suggested by consideration of sites of egg deposition, accessibility of eggs, plant habit, vegetative and flowering, and, particularly, the known oviposition-flowering relationship of Heliothis moths. The latter has an important bearing on the persistence of host material and governs opportunity for the intervention of parasite progeny in increasing numbers.

Records on the status of egg parasitism have been taken in conjunction with investigations of the extent of larval mortality associated with the various types of crop. The rôle of egg parasites as agents reducing the issue of moths from winter and spring breeding areas is discussed briefly. Comparisons are given to show that the influence wielded is inappreciable even in some cases where parasitism is particularly high.

An account is given of four gall midges whose larvae damage the seed of cocksfoot, viz. Contarinia dactylidis (H. Lw.), Dasyneura dactylidis, Metcalfe, Sitodiplosis dactylidis which is described from England and Ireland in the present paper, and Stenodiplosis geniculati, Reuter. The occurrence of predacious midges of the genus Lestodiplosis is also noted.

A short section is devoted to characters by which these midges can be distinguished.

Stenodiplosis geniculati is recorded from one English and two Irish localities on cocksfoot grass for the first time, hitherto it has always been recorded from foxtail. These midges, together with some experimentally bred on cocksfoot from foxtail parents, exhibit the typical characters of this species.

A new variety, Stenodiplosis geniculati var. dactylidis, is described from cocksfoot in New Zealand.

In a discussion of the host-plant specificity of gall midges attacking grass seeds, it is suggested that the present discovery of S. geniculati on cocksfoot in England and Ireland and the occurrence in New Zealand of this new variety exhibiting distinct morphological characters are two steps in the evolution of a new species.

I am indebted to Miss F. M. L. Sheffield for taking the photographs used to illustrate Plate IV. They were taken to show the comparative lengths of the antennal segments and not the chaetotaxy. I am also indebted to Mr. P. S. Milne who took the photographs used to illustrate Plate V.