Doubt exists as to why, in endemic areas, a varying proportion of calves die of East Coast fever while others survive. A series of experiments was therefore conducted to ascertain if the number of infected Rhipicephalus appendiculatus engorging simultaneously on susceptible calves influenced the course of East Coast fever reactions. The ages of the calves used in the various experiments varied, but other conditions were kept as uniform as possible.

When ten calves were grazed in a 1-acre paddock where the number of infected R. appendiculatus was high, eight died of acute East Coast fever.

In the second experiment, seventeen calves in all were grazed in the same paddock. These calves were given some protection from infected R. appendiculatus infestation, as two of the calves were immune to East Coast fever and the ears of ten of the susceptible calves were sprayed with tickicidal solutions. Four died from acute East Coast fever and one of subacute East Coast fever complicated with a helminth infection.

Confusion exists as to whether the immunity produced by one attack of East Coast fever is absolute or whether it requires to be maintained by reinfection.

During the present experiments mild transient infections have been produced in six calves, and in five cases the immunity has been incomplete and second attacks have followed reinfestation by infected ticks.

The time interval between the attacks has varied from 1 to 16 months, and it is suggested that when the interval is prolonged the second attack will be severe and may be fatal.

It is concluded that the durability of the immunity depends on the severity of the original attack, being durable when the attack is severe, and only transient and probably never solid when the attack is mild.

The temperature reaction is at the moment the best indicator as to the severity of the attack and the type of immunity evolved.

The reactions of the house-fly larva to four environmental factors, namely temperature, air humidity, smell and light have been studied in the Laboratory. It was hoped that the results would shed some light on the general behaviour of the larva in its normal habitat. A comprehension of this behaviour will assist in understanding the ecology of the species, and hence facilitate its control. In order to analyse the behaviour of the larva, its reactions (other than to light) were first studied in relation to one factor at a time. An attempt was then made to test experimentally its reactions to various combinations of factors.

The descriptions which have been given by travellers leave no doubt that land-leeches can cause considerable annoyance, and that the protective garments and substances that were applied by them to the skin and clothing were unsatisfactory. It was thought that other and more elaborate clothing would not supply the answer, as they would be hot and uncomfortable to wear. Accordingly, a search was made for an efficient repellent. Altogether seventy-eight substances were examined, and of these hydroxycitronellal was the most powerful but expensive and not readily obtainable. Di-methyl phthalate was efficient and the most generally useful. As di-methyl phthalate is a liquid which easily escapes from containers, creams incorporating the substance were evolved. Formulae for these creams are given.

1. The introduction refers to the fragmentary state of our knowledge on Trombiculid mites and indicates that most attention has been devoted to the taxonomy and bionomics of the group. The life cycle and general method of feeding are briefly outlined and reference is made to previous work directly concerned with the present treatise.

2. The morphology of the organs related to the phenomenon of piercing and sucking in the larva of Trombicula autumnalis is described.

3. The physical factors of the skin influence the choice of habitat upon the host.

4. The food consists of tissue fluid and disintegrated cells of the malpighian layer partially liquefied by the action of injected saliva, a condition typical of extra-intestinal digestion.

5. The mechanism of the initial piercing of the skin, which is done by the cheliceral claws, is described.

6. A tubular tissue canal is gradually formed in the skin of the host and around its insoluble wall are deposited superimposed layers of keratinized protective tissue.

7. The mechanism of suction is described and the factors which play a part are considered. The problem of the tissue canal serving as a duct for both the ejection of saliva and the suction of food is explained by the alternation of the two processes. The inter-relationship, between the intermittent injections of saliva, the formation of the tissue canal and the deposition of protective tissue, is elucidated.

It was noticed that some stock cultures of Laemophloeus minutus Olivier and L. ferrugineus Stephen were showing an abnormally high mortality. The numbers of living larvae appeared to decrease, many pupae died inside their cocoons and most of the few adults which emerged died within a few weeks. As adult Laemophloeus live for about 6 months at the conditions under which the cultures were kept (25° C. and 70% r.h.) it was apparent that something was killing the beetles at all stages in development. Microscopic examination of dead larvae and adults which had been chopped up and mounted in Berlese's fluid (Swan's formula) revealed huge numbers of the lemon-shaped spores (sporocysts) or pseudonavicellae of a sporozoan parasite. Living larvae from infected cultures were dissected in saline, and smears were fixed in Bouin's fluid (aqueous) and stained with Heidenhain's haematoxylin. Other larvae were fixed in Bouin's fluid, sectioned, stained with Ehrlich's or Heidenhain's haematoxylin and eosin, cleared in xylol and mounted in Canada balsam. These preparations revealed various stages of a schizogregarine which appeared to be Mattesia dispora which was described by Naville (1930) from Ephestia kühniella Zell. (Lepidoptera, Phycitidae) and recorded by Musgrave & Mackinnon (1938) from Plodia interpunctella Hbn. (Lepidoptera, Phycitidae). Careful examination of sections and measurement of various stages confirmed this identification. All stages were found, with the possible exception of young gamonts formed by macronuclear schizogony.

The plerocercoid larvae of Grillotia heptanchi (Vaulle-geard) used in the present study were obtained from the right supra-orbital lateral line canal of a specimen of Merluccius merluccius (L.). Two larvae were located in the canal in the region of the frontal bone and two in the region of the nasal. All were alive and were found to expand and contract slowly on removal. Unfortunately, the exact locality from which the fish came is not known as it was obtained from a fishmonger at Cardiff, but it is fairly certain that it was caught off the west coast of the British Isles.

1. In a mixed infection in which Haemonchus contortus, Ostertagia circumcincta and O. trifurcata predominated, the lengths were plotted against widths of eggs obtained from faeces.

2. Two-dimensional groups approximating to normal frequency distributions, showing little overlap, were observed.

3. The statistical ranges of means plus and minus twice the standard deviation for the two groups barely touched. These were, to the nearest micron, 68–84 by 41–51 for Haemonchus contortus and, for the Ostertagia group, 83–103 by 46–52.

In the course of studies of copepods parasitic on the market fishes of South India two of the most valued fishes, Scomberomorus commersoni and Stromateus niger, were found infested by large numbers of the blood-sucking parasites, Pseudocycnus armata Bas-sett-Smith and Lernanthropus konigii Steenstrup & Lutken. In the present paper the description of Pseudocycnus armata, which was first recorded by Bassett-Smith from Bombay and later by Kirtisinghe from Ceylon, is confined to a more accurate account of the appendages than has been given by these authors, while Lernanthropus konigii, which has not been recorded since it was established in 1861, is fully described.

1. Spermatophore production in Rhodnius and Triatoma is a structural adaptation for copulation and sperm delivery.

2. In Rhodnius a certain amount of sperm is stored in the spermathecae while the remainder is ejected with the collapsed spermatophore about 12 hr. after copulation. Hypergamesis never occurs.

3. The secretion in the male accessory glands was found to disappear if males were kept unfed for about 60 days. Such males were unable to copulate.

4. An average of ninety-eight fertilized eggs was produced as a result of one insemination by a young male. Four such inseminations at intervals of 45 days are, therefore, necessary to secure fertilized eggs throughout the entire life of the female. In nature repeated copulation is the rule.

5. The first spermatophore produced by males starved for 21–28 days was found to be as efficient as that produced by recently emerging well-fed males.

6. A male is capable of producing a great number of spermatophores; as many as fifty were obtained. Probably spermatophores produced by old males, although they contain a great number of sperm, lack sufficient of some substance necessary for fertilizing the eggs.

1. The area (Fig. 1) may be divided into a forested uninhabited mountain region, a region of low hillocks with between them marshy bottoms, many of which had been cleared and cultivated, and a flat coastal plain protected from the sea by a wall which leaked. Rain fell from early June till late September, and the rest of the year was mainly rainless.

2. Little is known about the mountain region. A. minimus was found infected in April, at which time, however, most potential breeding-places were dry. Larvae of A. maculatus were abundant, but the adults did not bite man.

3. Malaria was intense locally in the hillocks and coastal plain region, but uneven in distribution (Fig. 1). Evidence of active transmission in March and April, during the rains, and in October was found, there was a lull in May and June, but any other lulls there may have been were not discovered, since observations through the year were not possible.

4. Observations at night revealed A. leucosphyrus, A. jeyporiensis and A. minimus near man and rarely near cattle. A. sundaicus, A. philippinensis, A. annularis and A. hyrcanus attacked both man and cattle, though some, at least, would attack man only in the absence of cattle. A. aconitus was found near man at night, but nearly all the specimens contained old blood.

5. A. subpictus and A. vagus fed on cattle and entered houses at dawn in search of shelter for the day. The man-biters mainly sought shelter in some outdoor resting-place. The conclusion was that the standard practice of searching for mosquitoes in houses early in the morning gave results which were not only valueless, but misleading (Fig. 2).

6. Few dissections were made and sporozoites were found only in A. jeyporiensis (2/126= 1·6%), which was thought to be responsible for most of the malaria transmitted early in the year. It is suggested that the results of night catching provide valuable circumstantial evidence about vectors.

7. The night catches also gave information about time of biting, and yielded two observations of importance in control work. A. minimus, A. jeyporiensis, A. philippinensis and A. sundaicus did not attack until several hours after nightfall. A. philippinensis, in late May, when it was not raining, preferred to bite persons sleeping out of doors. Elsewhere it was observed that A. philippinensis did this and also did not rest nearby before or after feeding as other species did. It might, therefore, avoid a contact insecticide. A. sundaicus, baulked of a feed by night, attacked after sunrise.

The systematic position of the blood-sucking Gamasides Leach, 1815, is still very unsatisfactory. In his work on external parasites, Ewing (1929) recognizes the two families Parasitidae and Dermanyssidae, distinguishing them chiefly by the form of the chelicerae. The former family to which Laelaps and related genera belong is defined by Ewing as follows: ‘chelicerae of a generalized type having the tips incurved and being provided with teeth, and the fixed arm usually bearing a seta near its tip’. The Dermanyssidae have modified chelicerae, ‘usually without teeth and fixed arm always without setae’. In this family Ewing puts the genera Liponyssus, Dermanyssus and related ones.

This paper describes the terminalia of two abnormal males of the genus Sarcophaga Meigen (Sarcophaga similis Meade and S. hirtipes Wiedemann var. orchidea Böttcher) which appear to throw light on the interrelationships of the inverted, curvilinear and circumverted types of terminalia in Diptera. The specimens resemble certain stages described by Crampton (1944) in his comparative study of the morphology of the terminalia, and may perhaps represent stages in the pupal development of normal calypterate cyclorrhaphous Diptera.

From a study of the pregenital plate in these forms it seems probable that, in Sarcophaga at least, it represents two fused sclerites—probably sternites 7 and 8.

In March 1947 I collected a number of digenetic trematodes from the gullets of Cantherines setosus (Waite) and Cantherines güntheri Macleay. Three individuals of each species were examined and two of each were found to contain four or five trematodes. The fishes are known locally as ‘Leather-jackets’, and were taken from the shallow coastal waters of southern Tasmania. The parasites appear to be Lintonium vibex (Linton, 1899) Stunkard & Nigrelli, 1930.

In a paper entitled ‘Crithidia sp., parasitic in the alimentary tract of Cenaeus carnifex’ (Gibbs, 1942), an attempt was made to describe a flagellate found in the mid-gut, hind-gut and rectum of a plant-feeding insect which is common in the Cape Peninsula, South Africa. It was shown that leishmanial forms and bodies described as mould-spores were carried around attached to the flagella of leptomonads. It was also observed that, in some form, the parasite was resistant to desiccation, as nymphs became infected when allowed to feed on the dried dejecta of infected insects. Large, fast-moving leptomonads were described as being the only forms found in the mid-gut, while smaller leptomonads with the attached bodies, as well as crithidial forms, were found in the hind-gut. The rectum was not studied on account of the difficulty then experienced in removing it unruptured.

1. The following new species were encountered in this investigation:

Haemogregarina hamata in Lacerta jacksoni;

Hepatozoon minchini in Crotaphopeltis degeni

Pirhaemocyton granosa in Agama colonorum

Atoxoplasma argyae n.gen. n.sp. in Argya rubi-ginosa

Spirochaeta harveyi in Cercopithecus aethiops.

2. Further information is given in regard to the following known species, including new host records:

Plasmodium pitmani in Mabuia striata and M. maculilabris

Trypanosoma martini in Mabuia maculilabris

Plasmodium vaughani in Othyphantes reichenowi

Plasmodium relictum in Othyphantes reichenowi and Passer iagoensis

Haemoproteus wenyoni in Passer griseus

Leucocytozoon sp. in nine species of birds

Hepatocystes epomophori in Epomophorus labiatus

Hepatocystes kochi in Cercopithecus, etc.

Babesia pitheci in Cercopithecus mitis.

3. Exo-erythrocytic schizogony is described in Plasmodium pitmani of the skink (from spleen and heart preparations).

1. Formulae developed by Anfinsen et al. (1946) for a medium used in the cultivation of Plasmodium knowlesi were used for media in which excystation of Entamoeba histolytica without bacteria was investigated.

2. The following media were used: (i) an inorganic fluid containing carbon dioxide and chlorides, phosphates, and bicarbonates, of sodium, potassium, magnesium, and calcium; (ii) an inorganic fluid of chlorides and phosphates of the above metals without bicarbonates; (iii) the same respective fluids plus glucose, and (iv) the same plus enrichments with B vitamins, cocarboxylase, vitamin C, purines, pyrimidines, folic acid, glucosamine, cholesterol, and amino-acids. The oxygen content of all media was lowered either by cysteine or glutathione.

3. Some excystation occurred in all media, the percentages were lowest in the inorganic fluid without bicarbonates, highest in fluid with bicarbonates plus all of the listed organic compounds, and intermediate in the inorganic bicarbonate fluid plus glucose. Amino-acids were not required for good percentages of excystation.

4. Excystation occurred when cysts were isolated in medium with Trypanosoma cruzi.

5. The data show that organic compounds in the medium are necessary for high percentages of excystation.

1. A description of the morphology and life history (excluding metacystic development) of Entamoeba muris is given.

2. The descriptions of species of amoebae found in rats (Rattus norvegicus and R. rattus) and mice (Mus musculus) by previous authors are critically discussed, and it is concluded that one species, Entamoeba muris, is present.

3 Experiments on cross-infection of rats and mice with E. muris are described, together with observations on the course of these infections.

4. The transference of an amoeba morphologically similar to E. muris from Cricetus auratus to rats and mice is described.

5. An account is given of unsuccessful attempts to establish an infection of Entamoeba coli in rats and mice.

6. Observations on the incidence and hostrestriction of E. muris are discussed.

7. The affinities of E. coli and E. muris are discussed and it is concluded that, although E. muris resembles E. coli morphologically, it differs from E. coli on physiological grounds.

The author (1943) published a paper under the title ‘Genera and Species of Parasitic Mites (Acarina)’. This paper has been in great demand by workers interested in the parasitic Acarina and the number of separates was speedily exhausted.