An investigation of the seasonal incidence of I. ricinus on cattle in N.W. Cardigani shire showed that there are normally two peaks of activity, one occurring in spring and the other in autumn. The infestation curve varied considerably from farm to farm according to the husbandry methods practised. Delayed stocking of infested pastures caused an initial higher infestation of the cattle but, except on one farm, did not prolong the infestation beyond the normal period of tick activity. A lower infestation in spring than in autumn occurred on two farms. This resulted from either the lighter stocking of the infested grazings in spring than in autumn or the partial exhaustion of unfed tick population by sheep grazing with the cattle during the spring only.

There was no evidence for the occurrence of a unimodal curve of tick activity in the region studied.

Ixodes ricinus is the common tick infesting farmstock in Wales. Dermacentor reticulatus is recorded on cattle and sheep on two farms in N. Cardiganshire.

I. ricinus is widely distributed in the four major grassland zones of N.W. Cardiganshire. The most extensive areas of tick infestation are found on the marginal and hill farms. In lowland areas, except on extensive stretches of marshland, infested pastures are confined to isolated tracts of badly managed or poorly drained land. Infested grazings are invariably “rough” and contain one of the following plants as dominant: Festuca spp., Agrostis spp., Molinia caerulea, Nardus stricta, Pteris aquilina or Juncus spp. The degree of infestation of cattle depends on the relative area of the available grazing land colonised by the tick. Continuous stocking of infested pastures results in heavy infestations and vice versa.

Bovine piroplasmosis is the major tick-borne disease in N.W. Cardiganshire and predominates in the lowland districts. Outbreaks of the disease on marginal and hill farms are generally infrequent. Reasons are suggested for this phenomenon. Tick pyaemia is confined to lambs on hill grazings. The incidence of this disease is low.

The distribution of the tick in Wales and the border counties of Hereford and Salop shows a general relationship to areas of rough grazing. The tick is widespread in the western counties and is almost absent in the border counties. Radnorshire and Breconshire are interesting in that they have few infested farms in relation to the extensive nature of the “rough” grazing. A survey has also been conducted of the incidence of bovine piroplasmosis in Wales.

The brackish water form of A. gambiae on the East African coast—and probably in Mauritius—is not the same as A. melas of West Africa.

In salt-water gambiae a variable proportion of the females have an additional dark band on the palps, resembling 4-banded melas, but the remainder are indistinguishable from typical gambiae.

Eggs and larvae of salt-water gambiae show no morphological differences from those of fresh-water gambiae, thereby differing from A. melas of West Africa.

Larvae of the two forms show a clear-cut difference in reaction to sudden changes in salinity, and a simple test has been worked out whereby wild-caught females can be accurately identified by the reactions of their progeny.

This physiological test has formed the basis of all work in comparing the incidence, habits, and infectivity of salt and fresh-water gambiae in Dar-es-Salaam.

Exposed to equal chances of infection in the same village during 1947 and 1948, fresh-water gambiae had a sporozoite rate of 9·4 per cent. while that of salt-water gambiae was 0·8 per cent.

About 4 per cent, of both forms were infected with filaria larvae, but monthly figures showed that infection rates in salt-water gambiae may rise to 22 per cent.

Fresh-water gambiae show little tendency to leave African houses at dawn after feeding, whereas in salt-water gambiae over one-third of freshly blood-fed females leave the house at dawn.

In fresh-water gambiae many half-gravid females leave the shelter of the house at dusk on the night after the blood feed. There is no marked difference in infectivity between those which leave the hut and those which remain indoors at this stage.

Blood-fed and gravid females of fresh-water gambiae, funestus, and salt-water gambiae have been found in outdoor resting places, gravid females predominating in the case of the first two.

Although larvae of salt-water gambiae can complete their development in pure sea water, in nature increasing salinity becomes a limiting factor before it reaches that of sea water, continuous breeding being no longer possible at salinities over 83 per cent. sea water.

Salinity as a limiting factor explains the rather restricted breeding of salt-water gambiae on the coast, and suggests that certain coastal fresh-water swamps at Dar-es-Salaam could be cleared of all Anopheline breeding by salinifying with sea water.

A controlled technique is described, whereby the comparative protective values of various dips and sprays used in sheep maggot fly control can be accurately assessed.

In order to determine the exact mode of action of the agents under test, each is examined from the point of view of its power to inhibit oviposition by the adult fly and also for its larvicidal properties.

The “anti-adult” test involves the weekly exposure of treated groups of sheep to an active and dense fly population, maintained in a closed chamber under controlled conditions of temperature and light.

The larvicide test is a modification of a former method of larval implantation, and is applied to the sheep when the “anti-adult” protection, indicated by the previous test, is found to have failed.

In the second part of the paper, a number of results are presented which serve to illustrate the working of the technique, and demonstrate the comparative value of several methods of maggot fly control which are in current use.

A dip containing 0·5 per cent. DDT in water suspension was found to give the most satisfactory protection, and to achieve this result purely by its action against the adult fly. A 0·5 per cent. DDT benzene emulsion dip was less satisfactory, as alsowas spraying as a method of applying the insecticide. In general, spraying has given about half the protection of dipping, whilst on sheep in full fleece, the application of half a gallon of spray was found to be inadequate. Protection was again found to be poor when the fleece was carefully dressed with half a pound of a dry powder containing 5 per cent. DDT.

In contrast to DDT, BHC and arsenic were shown to possess virtually no “antiadult” properties at the concentrations tested. BHC and arsenic both acted as efficient larvicides and provided a valuable and similar degree of protection against the sheep maggot fly, as an incidental effect, when they were tested at the concentrations normally used for their primary function of sheep scab control.

Some of the structures illustrated here have already been noticed in two previous papers (Jackson, 1948a & b). All the present drawings were made by one of us (E.B.) from living material of Glossina swynnertoni Austen. The eggs and the first- and second-instar larvae were dissected from wild female flies and examined in saline under the microscope; the third-instar larvae were obtained by keeping females in captivity until larviposition occurred, normally in the late afternoon.

Hofmannophila pseudospretella is widely distributed in this country. It is a minor pest of stored foodstuffs, clothes and furnishings, and under certain conditions may give rise to a major infestation.

The egg stage is characterised by a high sensitivity to temperature and almost complete indifference to humidity. The incubation period varied from 110 days at 10°C. (90 per cent. R.H.) to 8·5 days at 27°C. (90 per cent. R.H.) and from 9·8 days at 90 per cent. R.H. (25°C.). to 14·0 days at 8·5 per cent. R.H. (25°C.). The percentage survival was greatly reduced both at very low (<3 per cent. R.H.) and at very high (100 per cent. R.H.) humidities. The survival of eggs from a single female varied from 56 to 97 per cent. under favourable conditions.

The duration of the feeding larval stage varied between 145 days at 13°C. and 71 days at 25°C. (at 90 per cent. R.H. on middlings). Larvae failed to mature below 80 per cent. R.H. at all temperatures. Larvae were reared successfully on a wide range of diets of both animal and vegetable origin, some predominantly carbohydrate, some almost entirely protein. The most rapid development occurred on dead adults and the slowest upon leather and yeast.

Under most conditions fully grown larvae entered diapause. This was characterised by a diapause moult after which the larvae assumed a typical diapause appearance. The length of the diapause was extremely variable and was determined largely by the temperature during larval growth. Larvae grown at low temperature did not enter diapause when incubated at 25°C. as fully grown larvae. The diapausing larvae were remarkably resistant to desiccation.

The duration of the pupal stage is affected by temperature but not by humidity. It lasted 98 days at 10°C. and 13 days at 28°C.

The total length of the developmental period was highly variable because of the variability in the length of the diapause under constant conditions. When the conditions throughout were 25°C. and 90 per cent. R.H. the total developmental period varied between 152 and 266 days, and at 20°C. and 90 per cent. R.H. the figures were 192 to 440 days. The developmental period was approximately 12 months under field conditions.

Under crowded conditions, mating was observed between males of H. pseudospretella and females of Endrosis lactella but none of the eggs developed.

The weight of the female at emergence was the most important factor governing the number of eggs laid. Weight of females varied between 8·2 mg. and 43·6 mg. and the egg number between 106 and 657 at 25°C. and 70 per cent. R.H. The number laid was significantly reduced at lower temperatures (10°C.) and at lower humidities (20 per cent. R.H.).

The sex ratio was found to be approximately 1:1, with a slight predominance of females.

The longevity of the fertilised adult female depended upon its weight at emergence and upon the physical conditions. Variation in weights of males was small, and the length of life of mated males could be correlated directly with the physical conditions. The mean longevity of mated females of all weights was 11·9 days at 25°C. and 70 per cent. R.H., 19·0 days at 15°C. and 70 per cent. R.H. and 9·4 days at 25°C. and 20 per cent. R.H. At 25°C. mated males lived 7·1 days on the average, and 18·8 days at 15°C.

The only important predator was the mite, Cheyletus eruditus, which destroyed numbers of eggs and young larvae.

Methods of approach to the control of I. ricinus by acaricidal action are outlined, and the type of acaricide for the control of ticks on dairy stock is discussed.

Dairy cattle were treated against ticks. Arsenic and carbolic washes were avoided for specified causes. The results of using (i) derris (5·5 per cent, rotenone), (ii) 0·5 per cent. DDT, (iii) DDT in a mixture with pyrethrum, talc or kaolin base, and (iv) pyrethrum (0·9 per cent. pyrethrins I and II) in aqueous solution show that (i) had a greater residual toxicity when applied to cattle, (ii) produced erratic results, which at present do not permit of specific recommendations. When DDT is employed in conjunction with pyrethrum as a powder (iii) the effective duration is low, and this is true also of pyrethrum as an aqueous wash (iv).

This paper is mainly an account of the known distribution of the 36 species and eight varieties of Phlebotominae found in the Sudan. Their economic importance is briefly discussed.

“Gammexane” and DDT, have many advantages over arsenic as tick killing agents. “Gammexane” dips have been used successfully to control the one host arsenic-resistant blue tick, B. decoloratus (Koch) but these dips have not been fully investigated for the control of two- and three-host ticks. The control of the three-host bont tick, A. hebraeum, a vector of “heartwater”, a disease of cattle, sheep and goats, is of great economic importance to South Africa. Larvae and nymphs seem to occur on cattle to a lesser degree than adults, but each stage shows a definite preference for particular sites on the host. For this reason, control measures have to be mainly directed against the adult stage. The effect of “Gammexane”, DDT and arsenical dips, and combinations of these, has been investigated, by making weekly counts of adults on treated and untreated groups of animals. Dipping has been compared with spraying, and the results have been examined in the light of chemical analyses and biological tests with the same samples. The experiments were spread over two consecutive years.

Preliminary experiments indicated that all treatments markedly reduced numbers of male bont ticks on the cattle. Weekly arsenical treatments with 0·16 per cent. As2O3 either by dipping or spraying did not reduce the numbers of females, nor did a composite dip-wash of 0·16 per cent. As2O3 and 50 p.p.m. gamma isomer. Dipping in 50 p.p.m. gamma isomer gave slightly better results against females than the above treatments. Encouraging results were obtained by spraying cattle with freshly diluted wash containing 50 p.p.m. gamma isomer, but dipping in 100 p.p.m. also gave satisfactory results. The relative ineffectiveness of dipping as compared with spraying, was found to be due to the loss of biological activity of hexachlorocyclohexane in dipping tanks, where complicating pollution factors appeared.

The results of the preliminary experiments were largely confirmed by the second series. Males always outnumbered females in collections where the ticks were removed week by week from cattle. The collections were taken to represent the rate at which cattle became re-infested, and formed a basis on which to gauge the effectiveness of treatments. Males increased in numbers week by week on other untreated control groups of cattle, and eventually greatly outnumbered the females. This suggested that males remained on the hosts longer, and were recorded more than once in the consecutive weekly counts.

All treatments reduced the numbers of males. Weekly treatments in 0·16 per cent. As2O3 did not reduce the numbers of females, nor did it prevent them from engorging. Some females laid after removal from cattle so treated but the eggs were sterile, whilst females in a similar state of engorgement, removed from untreated animals, laid fertile eggs. Arsenical treatments should thus eventually control bont ticks.

All “Gammexane” treatments appeared more effective than the arsenical treatments. Fresh dilutions of dispersible pastes and powders in the form of sprays gave better results than dipping in the same preparations at comparable concentrations. This was due to a loss in biological activity of the hexachlorocyclohexane as the washes became dirty with use in dipping tanks. This factor makes chemical determinations of dip-washes, based on total hydrolysable chlorine, of little value, unless these data are correlated with some suitable biological test. The addition of 0·03 per cent, copper sulphate in the wash did not prevent the loss of biological activity.

Oil emulsion dips, which were known to show a drop in the gamma isomer content with use in dipping tanks, were kept at the desired concentration and biologically active by adding fresh dip each week. In such cases both dip- and spray-washes gave satisfactory results when used at 100 p.p.m. gamma isomer. A combination of 50 p.p.m. gamma isomer and 0·16 per cent. As2O3 used as a dip-wash was not satisfactory in reducing the number of bont ticks, and little better than a fresh spray of 50 p.p.m. gamma isomer alone. The striking results given by a combination of a dispersible powder spray of 50 p.p.m. gamma isomer and 0·1 per cent. p,p′ DDT might be due to persistent action or repellent effect.

Arsenic is a stable substance and has been used for many years in dipping tanks to control ticks. It has disadvantages and in the case of the bont tick many females remained attached to the hosts when treated weekly in arsenic, although the engorged females laid sterile eggs. “Gammexane” preparations when used at 100 p.p.m. gave satisfactory results. These preparations, however, lost their biological activity in dipping tanks, and the best results were obtained when they were applied to cattle as fresh sprays.

A résumé is given of the recommendations hitherto made for the control of the Narcissus flies, Merodon equestris and Eumerus tuberculatus. Nevertheless, the control of these pests still remains a major problem in the British Isles. Laboratory and field experiments on the control of both these species were carried out in 1946 and 1947. In the field trials, dichloro-diphenyl trichlorethane (DDT), benzene hexachloride (BHC) and mercurous chloride (calomel) were included. The DDT and BHC were applied in the form of sprays, at a concentration of 0·5 per cent. suspension in water, over the aerial parts of the Narcissus plants and the surrounding soil on three separate occasions at approximately monthly intervals during the oviposition period, starting on May 10, some two or three days before the adult flies normally appear in the district. The calomel was applied in the form of a 4 per cent. dust on separate occasions during this period.

BHC and DDT were successful in producing a marked reduction in the degree of infestations by both species of Narcissus flies and, of the two insecticides, the former was apparently more effective. Although calomel dust afforded an appreciable protection against attacks by the Large Narcissus Fly, M. equestris, it exercised negligible control of the Small Narcissus Fly, E. tuberculatus, in these experiments. It seems from the results obtained in the present investigations that DDT and, in particular, BHC do provide a much more effective and practical means of controlling infestations of the Narcissus flies than any other methods hitherto tested.

The new genus Indomerus, described below, belongs to the group Calliptamini and is closely related to the group of genera characterised by a single tooth under the apical lobe of the cercus, but differs from all of them, except Paracaloptenus I. Bol. and Peripolus Mart., by the lobiform elytra. It differs from both Paracaloptenus and Peripolus by the broad, spade-shaped prosternal tubercle. From Peripolus the new genus differs also by the shape of the apical tooth of cercus, which in Indomerus is recurved backwards and covered by the upper lobe, while in Peripolus this tooth is lobiform like the upper lobe; from Paracaloptenus it differs by the excurved posterior margin of the pronotum which in Paracaloptenus is slightly incurved.

Mosquitos were exposed for short contact periods to deposits on plaster blocks from aqueous suspensions of insecticides.

There is an inverse relation between the size of ground DDT crystals fractionated into size ranges by sedimentation and their effectiveness. Smaller particles are more effective than larger ones even when equivalent numbers are compared. Differences in effectiveness are attributed to differences in the amounts of insecticide picked up and retained by the insect.

There is no significant increase in kills of mosquitos exposed for the same contact period to dosages of 10–20 micron DDT crystals above 3 mg. per sq. ft. “Persistence” of deposits of these crystals, however, increases as the dosage increases.

Crystal length alone is not critical, for fine 60 micron DDT needles are slightly more effective than ground crystals in the 10–20 micron range. The shape and mass of crystals together influence pick-up and determine their effectiveness.

There is also an inverse relation between crystal size and effectiveness of methoxychlor and DDD. The effectiveness of Compound 497 and of the gamma isomer of benzene hexachloride is influenced much less by particle size than is that of DDT.

The inert ingredient of a wettable powder has a masking effect on the insecticide, and this is intensified as the proportion of diluent to insecticide increases.

The availability of the deposit from an aqueous suspension of DDT crystals depends largely on the nature of the surface to which it is applied.

The genus Pseudiastata was described by Coquillett (1908) for a single species from Maryland, P. nebulosa, which he placed in the family Geomyzidae. Melander (1913b) referred it to the Drosophilidae and he has been followed in this by subsequent workers. The convergent anterior frontal bristles are suggestive of Milichiidae, however, and the genus may run to that family in some keys.

Brenthia leptocosma is a Microlepidopteron which feeds upon the Boraginaceous bush, Cordia macrostachya. This plant, since its accidental introduction into Mauritius about 1900, has become a pest of considerable agricultural importance. Other food-plants are C. myxa, C. abyssinica and C. holstii, which are all unimportant trees. B. leptocosma has been recorded only from Mauritius. It is not likely to be indigenous for it is restricted to Cordia species, none of which are considered to be native to Mauritius.

The morphology and biology of the various stages are described.

The distribution of B. leptocosma is that of its food-plants: it is extremely numerous in all regions below about 1,500 feet, which is the upper limit for C. macrostachya. The abundance of the moth is due to the excessive growth of C. macrostachya. Owing to its mode of life, it is of no value as a controlling agent of C. macrostachya.

Larval and pupal parasites are recorded.

A paper by the present writer on an Ichneumonid parasite of Hepialus lupulinus (L.) under the name Alomya debellator (F.) appeared in the last issue of this journal (1950). It now transpires that this Ichneumonid is not A. debellator but Ichneumon suspiciosus Wesm. This error was pointed out, as soon as the paper was published, by Mr. J. F. Perkins of the British Museum, and agreed by Mr. G. J. Kerrich of the Commonwealth Institute of Entomology, both of whom, as specialists in the Ichneumonidae, recognised the illustration produced from a drawing prepared by Mr. A. J. E. Terzi as representing a species of Ichneumon, probably I. suspiciosus. The actual specimen illustrated has been traced, and its identification has been confirmed by Mr. Perkins as Ichneumon suspiciosus Wesm. It is certain, moreover, that all the parasite material involved was this species and not A. debellator.