Descriptions are given of the tomato erineum mite, Aceria lycopersici, and the tomato russet mite, Vasates lycopersici, in Morocco, from which country the latter species is recorded for the first time.

A. cladophthirus is shown to be a synonym of A. lycopersici.

These two mites are almost world-wide in distribution and probably occur in most countries where tomatos are grown, but A. lycopersici has not been recorded from Australia or New Zealand.

Wild populations of Calandra granaria were allowed to oviposit on clean wheat and the tolerances of the eggs to mercury vapour were estimated. For six such populations the median lethal doses ranged from 55 mg.hr./m.3 to less than 1.0 mg.hr./m.3. A laboratory strain of grain weevils has developed resistance to mercury vapour in the egg stage, probably from contamination of an incubator. Such evidence as is available suggests that this resistance is associated with reduced chorion permeability rather than enhanced metabolic ability. The increase in resistance is such that no attainable concentration × time product will kill more than half the resistant egg population which is thus virtually in equilibrium with air saturated with mercury vapour. Fumigation of gravid females, or of wheat prior to oviposition, does not reduce the viability of any eggs subsequently laid.

An effort was made to determine the best conditions to achieve maximum saturation and persistence of small droplet insecticide (5-200 microns droplet diameter) within a type of African woodland. The problem is entirely one of atmospheric turbulence within the woodland. No attempt was made, or is likely to be fruitful, to introduce a detailed or mathematical argument. The relevant factors pertaining to atmospheric turbulence were observed and in some cases were directly compared with simultaneous observations made in the open.

The absence of zero wind speeds, considerations of changing lapse rates, bi-directional wind vane records, and visual observations of smoke, all combine to suggest that when conditions of calm or light winds exist in the free air, there is, under moderately dense woodland canopies, an almost continuous and slow transfer of air between the canopy and the ground, these movements tending towards laminar or sheet flows. With stronger winds, eddying about the trees swamps these gentle movements and air motion becomes erratic and turbulent, although such turbulence is less the denser the canopy. During the daytime there is notable horizontal movement of air towards clearings where convection is at a maximum.

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).

Attempts have been made to eradicate the tsetse flies G. morsitans and G. swynnertoni from two blocks of savannah woodland situated in the Central Province of Tanganyika.

The insecticides were applied from aircraft. Coarse aerosols were used, with mass median diameters of approximately 90 microns; droplet diameters varied from 4 microns to 250 microns approximately.

Eight applications of insecticides were made at intervals of two weeks. Each application was carried out at a nominal dosage of 0·25 gallons per acre, which was equivalent to 0·20 1b. per acre of the p, p'isomer of DDT or 0·03 lb. per acre of the γ isomer of BHC.

In the area treated with DDT it is possible that both species of flies were eradicated for a short period, but small populations were re-established there by immigrant flies. In the other block the reduction was not so great, but it is not considered that this was due to a lesser effectiveness of the BHC, but to a combination of circumstances that led to less effective applications.

Some general observations are made upon the use of aircraft for this sort of work, particularly in connection with the effect of meteorological conditions.

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.

Adults of Calandra granaria and C. oryzae have been fumigated with hydrogen cyanide by the methods of sustained pressure reduction and preliminary pressure reduction, the main criterion of response being death. Of the factors studied, starvation and sex of the insects are without influence. With pressure reduction, Haber's Rule relating mortality, concentration and period of exposure is not followed; for a given concentration-time product, the mortality is higher, the shorter the period of exposure.

Preliminary pressure reduction increases mortality much less than sustained pressure reduction. With the latter the mortality of C. oryzae is higher than that of C. granaria. The increases in susceptibility are largely accounted for by increases caused by pressure reduction alone in the absence of fumigant. The number of eggs laid by untreated females and by females surviving treatment was excessively variable and no discrimination between factors could be made.

Reference is made to the several species of scale insects which were pests on coconuts and to the Coccinellids which were introduced to combat them.

The introduction and life-history of Chilocorus nigritus is described.

The survival of the introduced Coccinellids and the part each has played in controlling the several species of scale is noted.

The habits of some indigenous Coccinellids are recorded.

The coconut-feeding Coccids of the Seychelles are listed and their economic role mentioned.

The incidence of “sooty-mould” and the species of Coccids responsible for its growth are discussed.

An estimate is made of the value of the control effected by the Coccinellids in terms of increased copra production.

Wheat of three moisture contents was fumigated with ethylene oxide, methyl bromide and hydrogen cyanide. Both chemical and biological assays were used to follow the changing distribution of the fumigant when applied with sustained vacuum, in a vacuum fumigation with simultaneous admission of air and fumigant, or at atmospheric pressure.

As these various factors were altered, in a multifactorial experiment, the changes in the fumigant distribution were also recorded chemically, and then analysed statistically. Changes in the mortality of both species of Calandra, either buried in a one-cwt sack of wheat or in the free-space, were estimated so that that part of the changes which was associated with the altered fumigant distribution was segregated by a covariance analysis and the remainder formed an estimate of the direct influence of the experimental Conditions on the susceptibility of the weevils to the fumigants.

When either ethylene oxide or methyl bromide is used as a fumigant for wheat, vacuum fumigation with simultaneous admission of air and fumigant gives results, in terms of the control of Calandra spp., which are almost indistinguishable from those obtained at atmospheric pressure under comparable conditions. When hydrogen cyanide is the fumigant, atmospheric fumigation is superior, quite apart from the capital expense and other practical disadvantages of fumigations at reduced pressures.

The effect on the eggs of the common furniture beetle, Anobium punctatum, to fumigation with hydrogen cyanide at a concentration of 4·25 mg./litre and four concentration/time exposures, varying from 4·3 to 42·5 mg. hr. per litre has been determined. Complete mortality was obtained in all cases. Comparison with data available for larvae show that the eggs are less resistant, from which it is concluded that commercial treatments adequate for infested wood will also kill eggs.

Experimental huts similar in construction to the dwellings commonly used in East Africa, but with exit window traps, were sprayed with various formulations of the three residual insecticides, DDT, BHC, and dieldrin, and the effect on the A. gambiae and A. funestus entering them was observed.

The almost complete absence of kill recorded by Muirhead Thomson (1950) in experiments in similar huts in Tanganyika treated with DDT Ditreen was not confirmed by these experiments.

A significant proportion of the A. gambiae and A. funestus entering huts treated with DDT did, however, escape unharmed, even immediately after treatment, whereas with the other insecticides, BHC and dieldrin, none of these mosquitos escaped the effect at least in the first month after treatment.

In preliminary experiments in which observations were carried on for nine months after treatments, BHC P.530 still showed some effect after seven months. This was almost certainly due to the fumigant effect of the small amount of insecticide still remaining below the wall surface. The irritant properties of the two DDT formulations, Ditreen and the oil-bound suspension “Supona” D, still existed after nine months.

In a second group of experiments, dosages of less than 80 mg. DDT and less than 60 mg. BHC (8 mg. of the gamma isomer) per sq. ft. gave over 50 per cent. kills of A. gambiae and A. funestus for only one month.

In a third group of experiments, using two formulations of BHC, five of DDT, one of a mixture of DDT and BHC and one of dieldrin:—

(a) Dieldrin was by far the most efficient insecticide and gave very high kills for over seven months.

(b) The DDT formulations, Murphy paste, Murphy wettable powder, suspensions of DDT crystals <30 μ and 30–70 μ in diameter, when applied to the whole internal surface of the huts, produced fairly high kills over the period of the observations (six to seven months), but significant proportions of the mosquitos escaped their action even immediately after treatment.

(c) The BHC formulations, P.520 and the oil-bound suspension “Supona” B, gave high kills for three to four months only.

(d) The mixture of BHC and DDT in oil-bound suspension “Supona” DB gave the high initial kill of BHC and the long-lasting moderately high kill of DDT.

(e) Against C. fatigans all the DDT formulations used in the third group of experiments gave very low kills, the BHC formulations high initial kills and dieldrin high long-lasting kills.

BHC has marked fumigant and particulate properties lasting for three to four months. Dieldrin has a remarkable particulate action, which produces for the whole six-month period of the experiment, very high kills among mosquitos suspended without actual contact with the insecticidal surfaces; DDT only shows this particulate effect to a slight extent.

It is probable that the differences in the toxicities to mosquitos of the insecticides used in these experiments is due partly to differences in the irritant properties of the insecticides. In the case of DDT many of the mosquitos having contact with this insecticide are irritated and escape from the treated surface before acquiring a lethal dose.

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.

The direct action of reduced pressures, in the absence of any fumigant, on C. oryzae and C. granaria have been investigated in glass chambers of about 1 litre capacity. C. oryzae is sufficiently sensitive to make the direct effect of reducing the pressure within the range 2 to 10 cm. mercury of some practical importance, but C. granaria is more resistant. Mortality of both species increases for exposure periods of up to 8 hr. and for increased temperatures from 20°C. to 28°C. A large part of the observed mortality must be associated with enhanced water-loss from the insects at reduced pressures, as little response occurs when the atmosphere is kept saturated with water-vapour.

All stages of Argas persicus were found in crevices in the bark of 49 of 266 trees belonging to 16 species in West Pakistan. These trees had not been used as roosts by domestic birds. The infestation seemed to be restricted to those trees used by vultures (Pseudogyps bengalensis) or herons (Ardea cinerea) for nesting or roosting. Several of the ticks collected contained recently sucked avian blood in the gut but intramuscular injection of crushed material from the ticks into a hen produced no blood infection.

Infested trees may be important as sources of the pest near poultry farms and chicken houses.

The behaviour of mosquitos in contact with deposits from aqueous suspensions of insecticides has been studied by allowing them to alight individually and measuring the time to the first flight.

Anopheles stephensi females flew from all formulations of DDT on various materials after approximately the same time of 2 to 4 minutes, but subsequent kills were high only when the deposit consisted of small (less than 10 microns) particles readily available for pick-up.

Mosquitos were also activated by contact with fresh deposits of BHC wettable powder P.520, but all died very quickly. They were not disturbed, however, by the vapour from BHC deposits, when contact was prevented, until in an advanced stage of intoxication. The time to the first flight from surfaces treated with BHC wettable powder increased as the deposits aged and varied with different materials according to the rate of loss by evaporation and/or sorption.

Mosquitos remained in contact with deposits of chlordane, dieldrin, aldrin and toxaphene for more than 30 minutes.

Experiments with a number of DDT analogues and BHC isomers indicated that lipoid solubility and molecular structure are two factors governing the rate of penetration of a compound.

The reactions of other species tested were similar to those of A. stephensi but kills of Culex p. molestus were significantly different from those of the Anopheline species after contact with deposits from a DDT wettable powder.

C. P. Clausen's and W. R. Thompson's concepts on the time factor in biological control are compared with the writer's experience. All three viewpoints emphasise the influence of environment correlated with time. As Thompson points out, we are almost always forced to ascribe the limitations of the numbers of pests to a combination of factors, biotic and physical, varying from time to time and from point to point. Clausen's views concerning the maximum time (three host generations or three years) necessary for an introduced parasite to demonstrate that it will be fully effective are supported by the observed facts. There is associated with the initial establishment of introduced parasites, however, a time lag that is not evident in the control of subsequent outbreaks. The principal factors are the attainment of an “equilibrium of distribution” and the rate of dispersal in building up a controlling density. When effective biological control can be anticipated, it is characteristic that marked outbreaks are brought rapidly under control, and the pest population then oscillates at a relatively low level. Several examples of fully effective parasites and their limitations are discussed which indicate that the value of a parasite or predator should be regarded not as a constant but rather as a variable.

An equilibrium of distribution is obtained when there is no decrease in the density of a parasite due to outward dispersal into the uncolonised area; the forward and backward surges of dispersal offset each other, producing a minimum uniformity of distribution independently of other influences. Parasites with slow dispersal rates produce an equilibrium of distribution and effective control more rapidly, but in a proportionately smaller area, than those with fast dispersal rates.

When these considerations are applied to the introduced, partially effective parasites of the gipsy moth, the time element is seen to be proportionately extended beyond the three-year period. After establishment, however, the effectiveness of these parasites is conditioned by the normal duration of the heavy outbreaks of the gipsy moth which rarely exceeds three years. Many of these enemies are as effective in the new environment as in the old. The degree of control of the gipsy moth achieved in the north-eastern United States does not differ greatly from that which occurs in central Europe. Examination of this relationship indicates that an enemy that is to become useful, but not completely effective, does not show its value within three years; consequently the adoption of Clausen's conclusions involves a danger of discontinuing programmes prematurely.

Theraptus sp. is widespread in the coastal region of British East Africa where it severely damages developing coconut fruits.

The female may lay over 100 eggs. There are five nymphal instars and, in the field, it is probable that about nine generations are produced each year.

Damage to coconuts is similar to that caused by Amblypelta cocophaga China in the Solomon Islands. Female coconut flowers and young nuts may be destroyed by a single feeding puncture. Damaged 10–16-week-old nuts may reach maturity but are undersized and often distorted by lesions from which gummy material exudes.

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 diamond-back moth, Plutella maculipennis, and Crocidolomia binotalis are the main pests of cabbage in Indonesia. Until 1951, good control was obtained with DDT sprays and dusts, but in that year growers near Lembang (Bandung) obtained poor results with DDT against P. maculipennis as compared with previous years. Investigations were started in Lembang, and also in Patjet (on Mt. Gedeh) where no difficulties had arisen. In laboratory experiments, a marked difference in susceptibility to DDT between a Lembang and a Patjet strain of P. maculipennis was demonstrated.

In field tests near Patjet with DDT, BHC and toxaphene, DDT gave satisfactory control and was better than the other two. At Lembang, however, where these three materials were again tested, but with derris and pyrethrum also, toxaphene was the most effective, followed by derris and BHC, while DDT, and also pyrethrum, gave almost no control.

For the time being, toxaphene and derris are recommended, the former during the growing season and the latter subsequently, but it is feared that resistance to toxaphene will develop. It may become necessary to resort to cultural and biological measures.