Considerable difficulties have been experienced in the past in keeping adults of the Red Locust, Nomadacris septemfasciata (Serv.), alive in cages for any length of time. No satisfactory explanation as to why they die in captivity has so far been given (Hamilton, 1936).

This paper is a study of the southeast Asian forms of the Anopheles hyrcanus complex with special reference to those of the Malay Peninsula, and it is to the latter forms that the detailed descriptions apply. The group is distinguished from all but a few other species by the presence in the adult female of a tuft of scales on the clypeus on each side, together with pale bands on the palps and a ventral tuft of scales on the seventh abdominal segment. For a complete diagnosis see page 6.

The usual practice has been to recognise only two oriental forms of hyrcanus: varieties sinensis and nigerrimus. It is shown that these varieties as recognised up till now are heterogeneous, and that at least in southeast Asia, ‘hyrcanus’, is a group of sibling species of which there are no less than seven or eight in the Malay Peninsula. For convenience, and where the exact species is not known, the name ‘hyrcanus’ in inverted commas is used, meaning hyrcanus sibling species group.

There is no doubt that these sympatric forms are distinct species for although individual characters, such as the width of the pale bands on the hind tarsi, are variable and the range of variation between two or more species may overlap, by using a combination of characters there is no difficulty in identifying individual adult specimens of either sex. Furthermore, offspring reared from eggs are always of the same form as the female parent. Larvae, pupae, and eggs can usually be identified, and keys are given for the identification of these stages as well as the adults.

Seven named species are described, but only one of these, A. crawfordi, is regarded as new, the others have all been described at various times, and the names later sunk as synonyms of sinensis and nigerrimus.

All seven species have been recognised also outside the Malay Peninsula, and some have a wide range from western India to the Philippines or Moluccas. Except for sinensis, the species belong to southeast Asia, where Assam, Burma, Siam, the Malay Peninsula and Sumatra support the largest number. A. sinensis also occurs in these countries, but the centre of its range is more to the northeast towards China and it does not appear to have penetrated further into the archipelago than the Malay Peninsula and Sumatra. Towards the limits of the Oriental region in northwest India and central and northern China, the southeast Asian species of hyrcanus are few or absent, and are replaced by other forms of hyrcanus of palaearctic type. In China, the name sinensis probably covers two overlapping forms, a southerly oriental one presumed to be Wiedemann's type form which lays a wide decked egg, and a northerly palaearctic form laying a narrow decked egg.

Species of which sufficient numbers have been seen from different countries show geographical variation. The effects of this variation are most marked in the relatively isolated Philippine Islands, where out of three forms occurring there, one, pseudosinensis, is regarded as a species peculiar to the Philippines, though clearly derived from the same stock as the widespread nigerrimus which does not occur there. A second, lesteri, is probably a subspecies of the form of lesteri found in Borneo and the Malay Peninsula. The group thus seems to conform to the classical pattern of speciation by geographical isolation. Much of the evolution and distribution of the species probably took place in pleistocene times.

Broadly speaking A. ‘hyrcanus’ can be described as a swamp breeder, with a preference for animal blood. But it is evident that the individual species show important differences in their biology. Some breed in sunlit waters and their larvae are often green; others seem to prefer shaded places, though not in jungle, and their larvae are usually dark coloured. A. sinensis and lesteri at least, can breed in moderately saline waters, sometimes in company with A. sundaicus and baezai.

It appears that most of the species will bite man freely out of doors shortly after dark, but are reluctant to enter rooms in search of human blood. However, the degree of reluctance to bite man probably varies to an important extent between different species. All species can usually be captured at night at cattle sheds. The adults do not often rest indoors by day, and the outdoor resting places of indiensis and lesteri are described.

In southeast Asia, though ‘ hyrcanus ’ is not one of the principal mosquito vectors of malaria or filariasis, it has been found infected on a number of occasions. In most cases the exact species cannot be determined now, but where this is possible, it has been A. nigerrimus Giles in every instance. Venhuis (1939) showed that his A. hyrcanus var. X (=nigerrimus) was a vector of malaria in Celebes and Java, and Kariadi (1941) implicated it in the transmission of malayan filariasis in southeast Borneo. In Malaya, examination of preserved specimens showed that nigerrimus was the principal or only vector during an outbreak of malaria at Kuala Lumpur which Hodgkin (1933) had shown to be due to hyrcanus, and recently nigerrimus has been found to play a part in the transmission of malayan filariasis in Kedah and Province Wellesley. Experimental infections with Wuchereria malayi, the worm which causes malayan filariasis, showed that nigerrimus was less readily infected than the principal vectors (Mansonia spp.), and some other members of the hyrcanus group, but that it bit the human carrier more readily than the latter. A. sinensis, though probably harmless in Malaya, is a vector of malaria and bancroftian filariasis in parts of China, but the exact identification of the vector is now in doubt, since there appear to be at least two forms in China included under the name sinensis.

A new member of the larch-feeding genus Anoplonyx has recently been described in Britain. The species, A. destructor Benson, has been common in British larch woods for some years without, however, causing any very serious amount of damage to the tree crops. Notes on the biology of the species, including larval descriptions, are given and the present forest status of the species is reviewed. Apparently unsuccessful attempts to achieve biological control by the release of Dahlbominus fuscipennis (Zett.) are recorded.

An account is given of damage in Kent to a lead cable and its drum by larvae of Ptinus tectus Boield. The original infestation resulted from the accumulation of discarded food in the drum hub. The mature larvae, in order to pupate, bored into the hub of the drum and the sheath of the cable, thus producing innumerable excavations and some perforations in the sheath of several hundred feet of cable.

During the past 12 years, records of beetles of the family Ptinidae as pests of stored products in Britain have been increasing in frequency. Kloet & Hincks (1945) record 21 British species of Ptinids, but of these, three species, Ptinus palliatus, Perris, P. pilosus Mueller and P. latefasciatus Gorh., have not so far been recorded from warehouses or stored products and a furthertwo species, P. lichenum Marsh. and P. subpilosus Sturm have only rarely been recorded from such habitats. The importance of birds' nests as reservoirs of pests of stored products is being shown in a paper to be published shortly by Woodroffe and Southgate who carried out a survey of the fauna of the nests of birds associated with buildings. They found that the fauna of such a habitat was extraordinarily similar to that of warehouses in this country and that very large numbers of several species of Ptinids were present. The risk of this habitat being a possible source of many Ptinid infestations can be gleaned from the following list of species which they found:—

Ptinus tectus Boield., P. fur (L.), P. sexpunctatus Panz., P. pusillus Sturm, P. subpilosus Sturm, Eurostus hilleri (Reitt.), Niptus hololeucus (Fald.), Mezium affine Boield., Trigonogenius globulus Sol.

The systemic insecticide Hanane (mainly bisdimethylamino fluorophosphine oxide) is readily absorbed by the trunk of a coffee tree and translocated to the foliage when the bark is lightly scraped and the chemical applied in solution on a pad of absorbent material covered with a waterproof skin to prevent evaporation.

Smaller dosages of Hanane are required to give equivalent control of Planococcus kenyae (Le Pelley), or to cause a similar degree of phytotoxic damage, by this method than by soil treatment.

Abrasion or removal of the bark before application enables a greater absorption of the chemical but leads to serious phytotoxic damage by a comparatively low dosage.

The two species of Mirids, Sahlbergella singularisHagl. and Distantiella theobroma (Dist.), are important pests of cacao (Theobroma cacao L.) in the Gold Coast. The damage sustained by the cacao is due, in part, to the direct effects of feeding by these insects, but more to the subsequent invasion of the resulting lesions by the weakly pathogenic fungus, Calonectria rigidiuscula (Berk. & Br.) Sacc.

In the field, Mirid damage may be classified into three categories. “Blast” is the result of light diffuse attack and is so named because of its similarity to fire damage. “Stagheaded cacao” is more severe, the trees showing numeroussmall crown branches but forming a poor canopy. “Mirid pocket” describes severe damage, normally limited to a small area, the trees losing the crown completely and the polelike trunks bearing numerous lateral chupons. In general, stagheaded symptoms are more prevalent where cacao is grown without shade, and pockets where cultivation of cacao utilises shade trees.

Consideration of the factors associated with Mirid damage shows that it is correlated with breaks in the cacao canopy. Evidence is brought forward to suggest that such breaks normally precede, rather than result from, Mirid attack. The canopy itself is unsuitable for the development of either species, the major part of the population being confined to the sub-canopy levels. The initial causes of the breaks are, most frequently, the die-backs associated with swollen shoot or with adverse water relations. The falling of shade trees causes a number of breaks, and, where cacao is grown without shade, the Mirids themselves may be a cause.

The most important single factor influencing the form of the cacao canopy, and thus the course of Mirid attack, is the amount of overhead shade, particularly that provided by trees little taller than the cacao itself. Shade which is too dense causes etiolation of the cacao and thus renders it susceptible to attack, the resulting damage generally taking the form of a pocket. Shade which is too sparse does not shield the cacao from the adverse effects of exposure. The Mirid damage in such areas generally assumes the stagheaded form.

It is suggested, from field experiments, that the invasion by Mirids of areas suitable for colonisation is not by random movements, but is determined by the change in some physical factor resulting from the broken canopy. Changes in light intensity are the most obvious results of such breaks, but further experiments are needed to determine which is the operating factor.

Degraded cacao is prevented from recovery, not by Mirid attack alone, but by the interaction of it with the presence of C. rigidiuscula, and by increased exposure.

The sampling methods employed are described, and the bearing of the results upon control measures is discussed.

A review of the literature is given which shows that changes in the susceptibility ofinsects to insecticides occur during development when the poison is applied as a fumigant, as a stomach poison and as a contact poison.

The assessment of changes in susceptibility to contact poisons is discussed. The basis of assessment may be the concentration required to kill a given number of individuals, or the amount of poison required to kill unit weight of insect material. The great majority of the earlier work used the former basis of assessment, but where the insect is changing in size and shape during development and hence changing in the proportion of surface area to body weight, this method has limited significance when the poison is applied as a spray of constant deposit evenly over the surface area. A mathematical method is given for transforming the results obtained in terms of concentration to kill a given number of individuals into weights of poison to kill unit weight of insect material. Rearingmethods are outlined which enable batches of various stages of Diataraxia oleracea (L.) (tomato moth), Tenebrio molitor L. (meal worm) and Periplaneta americana (L.) (American cockroach) to be obtained at a known age and stage of development.

Experimental results are given for a spraying technique using DDT and the pyrethrins as insecticides on the comparative resistance of the eggs, larvae and pupae of D. oleracea, the larvae, pupae and adults of T. molitor and the nymphs and adults of P. americana.

On the basis of the concentration of insecticide required to kill a given percentage of individuals, it is shown that great differences can occur in the resistance of different instars of one species and considerable differences may occur within the instar. If the data for the larval and nymphal instars are considered on the basis of the weight of poison required to kill unit weight of insect material, differences still exist but are much reduced.

When toxicity is estimated on the basis of the concentration of poison in a constant spray deposit required to kill a given percentage of individuals the overall variations of resistance during development measured for DDT in terms of median lethal concentrations were: —D. oleracea eggs and larvae fifty times (0·002 per cent.–0·1 per cent. w/v), the pupa proved resistant to 0·5 per cent, w/v; T. molitor larvae, pupae and adults thirty-seven and a half times (0·0008 per cent.–0·03 per cent, w/v.) and P. americana nymphs and adults eight and a half times (0·0035 per cent.–0·03 per cent. w/v). The figures for pyrethrins were: D. oleracea eggs, larvae and pupae thirty-seven times (0·0027 per cent.–0·1 per cent. w/v), T. molitor larvae, pupae and adult forty times (0·005 per cent.–0·2 per cent. w/v), and P. americana nymphs and adults ten times (0·00031 per cent.–0·003 per cent. w/v).

The figures show that the range of variation of resistance during development may be very large, over 250 times in the case of DDT and D. oleracea, where the pupa, is resistant. The maximum variation that was found within an instar was 16·6 times where the resistance to pyrethrins of the 1-day old pupa of T. molitor was compared with that of the 4-day old pupa. The data show that the amount of variation in resistance that can occur varies with the test species and with the insecticide. Furthermore that the order of resistance of the developmental stages of any given species will differ with the insecticide and that with any given insecticide the order will vary with the species.

It may be inferred from these data that any comparison between insecticides on one stage of development of one instar of one species will not necessarily hold true of any other stage of development of that species or of any other species.

Observations were made on the action of the insecticides on the various instars and the symptoms of poisoning are described. It was observed that DDT at the highest concentration used (0·075 per cent. w/v) failed to prevent the development of the embryo inside the egg-shell and death only occurred after the fully developed embryo had eaten the egg-shell which it normally does prior to emergence. Pyrethrins on the other hand if applied at sufficiently high concentrations could prevent embryonic development although at lower concentrations a high percentage of eggs formed fully developed embryos.

At the highest concentrations used neither DDT (0·5 per cent, w/v.) nor the pyrethrins (2·5 per cent, w/v.) were able to prevent pupal development, and partial emergence often occurred before death. DDT differed from the pyrethrins in that it was ineffective on the pupae of D. oleracea.

Using data given in the literature and from some preliminary experiments on respiration rates, it was possible to deduce some correlation between metabolic rate and susceptibility, and changes in the permeability of the cuticle and chorion and susceptibility, but the evidence is unsatisfactory and the causes of the changes in susceptibility await further detailed investigation.

In Trinidad A. aquasalis swarms over open areas, mostly grass, and over drains and not over scrub vegetation.

Swarming commences at a light incidence not exceeding 5 foot,-candles.

Mating has been observed in 54 per cent. of the swarms, the fertilisation index of females captured in them being 65 per cent.

The lag between the first sight of a swarm and the first observation of a mating pairaverages 6·5 minutes, the light incidence at commencement of mating being no higher than an average of 0·8 foot-candles.

Seventy species of Tabanids occur in the Sudan. Many of the inhabitants are pastoralists, and the Tabanids have a profound effect on them, largely by causing them to remove their animals from infested areas in the rains and to undertake extensive annual migrations. New problems will arise when economic development involves permanent settlement of certain infested areas. This paper sets out the problem, and satisfactory control measures have yet to be devised.

The country is briefly described.

The section on individual species consists mainly of lists of localities which are shown on maps.

In a general discussion of distribution faunal areas are designated for discussing Tabanids in the Sudan. The composition of the Tabanid fauna, which is mainly Ethiopian, is described. Types of habitat are indicated, and distribution is discussed in relation to systematic position. The area in which Tabanids are abundant, and their seasonal prevalence, are indicated.

There are brief references to habits, particularly the attraction to inanimate objects and the fact that some species bite man on some occasions and not others.

The economic effect, namely, the direct effect of bites and probable role of the flies in the transmission of cattle and camel trypanosomiasis and human loiasis, are described, mainly from published sources.

The effect of Tabanids on the distribution and annual migrations of pastoral tribes is described. Attacks by flies on domestic animals and the search for pasture and water are the main causes of the very extensive rainy season migrations which are shown on a map.

The problem of control is very briefly discussed.

Additional information on some of the foregoing subjects is given in notes on faunal areas.