Our knowledge of the distribution of tsetse-flies affecting domestic stock in Kenya Colony is of a very general character. A good deal of the information requires confirmation; and much needs to be done to ascertain the extent and the nature of the permanent fly-infested areas, and the seasonal dispersion of the tsetses from their permanent haunts.

This subject has been discussed very fully by Dr. T. A. M. Nash and the writer in two recent papers (Bull. Ent. Res. 24, 1933, pp. 135, 475–477). There is, however, one point which it is felt should be made clear. Dr. Nash states that the writer, “working in the Western Kondoa fly-belt, finds the more normal type of obvious concentration. In the dry season tsetse become more numerous in Berlinia-Brachystegia woodland immediately surrounding ‘vleis.’ Owing to the small size of these ‘vleis,’ which are only about 75 yards across, the fly appears to an observer to be concentrated in them; in reality they are probably living in the shade of the surrounding weeds and fly out to attack the investigator. Passing through Berlinia woods in this country one finds fly more numerous on the edge of “vleis,” probably because the trees are almost non-deciduous owing to sub-soil water.”

Hibernation of P. papatasii in Palestine is primarily caused by low temperature, but cyclical (? hereditary) factors exist which modify the phenomena of hibernation to a certain extent, as indicated by the following facts.

1. Occurrence of a gradually increasing number of resting larvae during autumn, with a maximum of hibernating larvae in the first winter generations.

2. A gradually increasing prolongation of development during the late summer generation, with a maximum duration of development in the first winter generations in larvae kept at 30°C.

3. The pupation of hibernating larvae kept at 30°C. in spring at the same time as of larvae kept in out-of-door conditions during the winter.

There is always a certain number of resting larvae (2 to 12 per cent.) throughout the summer in otherwise active broods. This inhibition of development shows that a latent inclination to diapause exists in all generations, and that diapause may also be brought about by unfavourable conditions.

No relation could be found between the interval between hatching and oviposition and asthenobiosis.

Many years ago Bezzi realised that the species placed in the genus Ceraiitis, MacL., needed division into smaller groups. Among those he first delimited, Carpoph-thoromyia, Aust., may well be retained as a genus, but most of the others, Parda-laspis, Bez., Perilampsis, Bez., Trirhithrum, Bez., etc., have hardly more than sub-generic value. It is therefore proposed to study all the species concerned in order to discover the true limitations of the groups; and also with a view to stabilising the species themselves for a further study involving dissection of specimens. The last point is of some importance because more detailed work on the morphology cannot be carried out at all satisfactorily until one is quite sure of the specific identity of the specimens used. Further, as the dissection of insect types may be undesirable and few institutions, if any, would allow it to be done, it becomes essential to have specimens critically compared with types, and until this is done, there must always remain some element of doubt in identifications. This paper is thus a beginning of a series on a nreliminarv studv of the subsrenera of Ceratitis.

During the last decade, entomologists have made progress in understanding the environment in which certain insects live; in particular, we begin to understand the effect of certain physical and chemical factors, which make up a part of the environment. With this gain in knowledge, it is sometimes possible to forecast outbreaks of insects and of diseases conveyed by them, and one can sometimes say that a particular alteration of the environment will result in loss or gain. But so far as mosquitos are concerned, one must admit that though much work has been devoted to the analytical study of the water in which the early stages are passed, the results are disappointing. A consideration of the published work suggests several reasons for this. Investigation into the ecology of the mosquito has had a vogue, and much of it has been done by workers who were isolated and whose knowledge of chemical technique and freshwater biology was limited. Apart from that, the inherent difficulties are great, for the worker must hunt for the limiting chemical and physical factors among a host of others which are doubtless unimportant, and there are few clues to indicate which of the chemical constituents of the water affects the mosquito. The data are therefore voluminous and it is difficult to reduce them to order and present them so that they can be readily understood.

♂♀. Derm piceous, shiny, with dense grey scaling more or less mottled above with dark brown patches.

Most of the mosquitos described here were collected by Dr. H. de Rook and the author during a tour of investigation of filariasis in the eastern part of the Malay Archipelago. The tour was undertaken with a grant from the “Koningin Wilhelmina Jubileum-Stichting” in Batavia.

The egg, the five larval instars, cocoon, prepupa and pupa of Bracon tachardiae, Cameron, are described.

Two series of larvae, one male and one female, occur, these series overlap very considerably and it is only towards the maximum and minimum of the range that larvae are respectively entirely female or male.

It is shown that the five larval instars of B. tachardiae may be grouped by the widths of the head-capsule, and that an instar can be characterised by the head-width, particularly if only averages are considered. The actual range of head-width in each instar is rather large, and in some cases the extremes overlap. In actual practice head-width is a safe indication of the instar of a larva as the extremes rarely occur; the widths calculated on Dyar's principle also approximate sufficiently closely to the observed widths to preclude the chance of an ecdysis having been overlooked.

The length of the mandible is for practical purposes identical in a larva of any given instar and in its exuviae. The larval instars and their exuviae can be grouped by the lengths of the mandibles, particularly if averages are considered; the range for a given instar is wide but the extremes do not overlap. The lengths calculated on Dyar's head-width principle approximate closely with the observed lengths, sufficiently so to preclude the possibility of overlooking an ecdysis, and making possible the identification of the instar of fixed and mounted specimens of larvae or exuviae, for which purpose head-width is useless.

The factors of increase of head-width and mandibular length are fairly similar, falling near to 3 √2 =1.26, and for practical purposes one may be substituted for the other, the calculated widths and lengths so obtained still approximating to the observed widths and lengths.

Various uses of this fact are indicated. Preliminary investigations point to the fact that similar observations apply to Aphrastobracon flavipennis, Ashm., an ectoparasite of Eublemma scitula, Ramb. It is suggested that similar observations may be true for other ectoparasitic Braconids.

The growth of the body of the larva from instar to instar is independent of the growth of the head-capsule, larvae increasing in weight and in volume by a figure lying between 3 and 4 times from instar to instar. The actual figure obtained theoretically for volume increase was 3–6. The head-size increases by the usual double at each moult.

Owing to the deposition of resin, the females assume two shapes, one somewhat circular in which the mouth-parts are situated ventrally about the middle of the body, and the other pyriform, in which the mouth-parts are situated at the extreme anterior end. In the former type of females the mouth-parts are posteriorly directed and in the latter anteriorly. The rostrum lies outside the body cavity between the anterior pair of oral lobes. The rostralis opens into the pharynx which lies in the tentorium. The oesophagus is elongated and passes into the colo-rectum to be succeeded by the convoluted ventriculus. The ventriculus on leaving the colo-rectum leads into the intestine, which is marked into the mid and hind intestine by the junction of the ampulla of the Malpighian tubes. The intestine after forming a loop round the greater part of the colo-rectum re-enters it close to the point of its commencement from it and continues closely attached to the outer side of the ventriculus from its distal to its proximal end; after this it comes out of the colo-rectum and runs alongside it to open into it near the anterior third of its length. The convolutions inside the colo-rectum are comprised of the ventriculus and the part of the hind intestine running outer to it. The “colon caecum” is absent. The colo-rectum opens at the anus situated at the posterior end of the insect and is divided into colon and rectum by the opening of the intestine into it.

The salivary glands consist of two branches of ovoid and spherical bodies. The common duct of the salivary gland of each side runs close to the ventral ganglion and joins the opposite duct to form the terminal duct near its anterior end, which then opens into the pharynx.

The nervous system consists of a bilobed cerebral ganglion which lies anteriorly to the mouth-parts in females in which the tentorium is directed posteriorly, and either laterally or ventrally to it in females in which the tentorium is directed anteriorly and lies at the extreme anterior end. The cerebral ganglion is joined by a pair of connectives to the ventral ganglion, which lies dorsal to the tentorium in females in which it is directed posteriorly, and posterior to the tentorium in which it is directed anteriorly and lies at the extreme anterior end. The ventral ganglion is followed by the nerve chord, which varies in length in either type of female. The main nerves arising from the central nervous system are described.

It was in December 1929 that the writer first tried to reduce the terrible mosquito nuisance which each winter plagues the City of Calcutta. His efforts were naturally confined to an attempt to alleviate conditions in the Bengal-Nagpur Railway's Headquarters Colony at Garden Reach, but it soon became obvious that by control in the relatively small area of land belonging to the railway very little could be accomplished, and that to achieve anything appreciable a very much larger acreage would have to be put under control. So when in the ensuing winter of 1930–31 other property owners in the vicinity became aware that this railway was attempting to do something and evinced interest in the matter, advantage was taken of this to form the Garden Reach Anti-Malaria Association, the initiation of which also received a considerable impetus from the virulent outbreak of malaria in the previous autumn at Budge Budge, some 18 miles down-river from the City. This outbreak, and the organisation of and area covered by the Association, are described by Covell (1932).