Many workers have described abnormal forms and structures in ticks. Neuman (1899) was the first who recorded some abnormal Ixodidae. Brumpt (1934) reviewed the literature and recorded some new interesting abnormalities. The posterior region of the body of one of the specimens described by Brumpt had two ani and four stigmata. Brumpt considered that only the Ixodidae display abnormal forms, but since then Robinson (1943–4) described abnormalities in laboratory-bred Ornithodorus moubata. He also noticed a ‘partially twinned’ tick which mated, and laid eggs which developed into normal ticks.

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.

A critical review is presented of the species of Dinobothrium and their probable synonyms. D. septaria v. Beneden and D. planum Linton are accepted as valid species. D. keilini Sproston and D. plicitum Linton are regarded as of doubtful status, the former being probably a synonym of D. septaria, while D. plicitum may be a synonym of D. planum. The type-specimens of D. keilini and of D. paciferum Sproston have been re-examined. A new interpretation is offered of the structure of the scolex of D. paciferum, and some other details of its anatomy are redescribed. A small species from Cetorhinus maximus is described, which is very similar to, and may prove to be identical with, Dinobothrium paciferum. As it apparently differs in having the neck and parts of the bothria covered with spines, it is treated as a distinct species and named D. spinosum. The question of the specific identity of the known larval forms of Dinobothrium is briefly discussed.

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.

Five main types of harvest mite larvae have been found in Great Britain. These may be distinguished according to the following key:

(1) Galeal setae ciliated

Galeal setae not ciliated (2)

(2) Scutal setae duplicated

Scutal setae not duplicated (3)

(3) Humeral setae duplicated Humeral setae not duplicated (4)

(4) Eight setae in both the second and

the third rows of dorsal setae Normal type a

Six setae in both the second and

third rows of dorsal setae Normal type b

Eight setae in the second dorsal

row but only six in the third Normal type c

Type a and type b may be further divided into groups based on differences in scutal width and setal length. Nevertheless, scutal width, setal length and setal number are not correlated with each other. Were larvae to be separated into two species on the hypothesis that one of these characters (e.g. differences in setal number) is genetically determined, then the range of variation with respect to the other two characters (namely scutal width and setal length) would be the same for each species. Forms with duplicated humeral setae do not differ otherwise from the normal type. The ciliation of the galeal setae and the duplication of the scutal setae is not consistent and larvae of mixed or intermediate type are known. It seems to me that these morphological differences may not be genetically determined but are solely phenotypic (and in the case of setal number may be influenced by rainfall and temperature). This, together with the lack of points of distinction among nymphs and adults, suggests that there is only one British species which was first described as Acarus autumnalis (Shaw, 17 90). As no type is known to exist, a lectotype has been selected from British material and deposited in the British Museum.

The systematic position of this species is difficult to determine. Until larvae of known ancestry can be reared under controlled conditions the systematic significance of the variations described above must remain in doubt.

Nymphs and adults do not appear to differ greatly from those described by André (1930). The adult is recorded for the first time in England. The male genitalia are described.

Previous work is discussed and described. The numbers of larvae present in a square yard of soil can be estimated by the use of caged guinea-pigs or by light traps. The infestation observed on the ears of wild rabbits gives a rough index of the population present in a given area.

Using a modified light trap, gorged larvae can be collected from their hosts.

Adults can be extracted from light, friable soils by flotation in water and from any type of soil by the Salt-Hollick soil-sampling machine.

The harvest mite occurs throughout the British Isles. It seems possible that climate and the geological origin of the soil do not affect harvest mite abundance. They are, however, less numerous on heavy clays.

Larvae are most abundant in late summer and autumn. Adults remain constant in numbers throughout the year.

The larvae appear to infest most warm-blooded vertebrates. They do not attack at night. Nymphs have been observed sucking the contents of nymphophanes.

Adults have been found at a depth of 3 ft. They appear to come nearer the surface in warm, moist weather, but are driven down by drought, heavy rain and ground frost.

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 cycle of vertical migration of the infective larvae of Haemonchus contortus on experimental plots of Lolium perenne S 24, kept out of doors, has been related to meteorological and micrometeorological factors.

2. The three main factors concerned with vertical migration are temperature, humidity and light intensity.

3. In the majority of cases the greatest number of larvae are on the grass blades in the early morning and in the evening, less being recovered at night and during the middle of the day. The time of the morning maximum becomes progressively earlier passing from winter to summer, and the time of the evening maximum progressively later. The reverse is true in the second half of the year.

4. Low and high temperatures accompanied by low humidity inhibit vertical migration on the grass.

5. High humidity (continuous precipitation) does not prevent migration, the two daily maxima are apparent, but the numbers climbing are less than in the absence of rain.

The literature on mosquito larvae as intermediate hosts of larval Trematodes is scanty. Porter (1938) states that it is well known that anopheline larvae act as intermediate hosts for Xiphidiocercaria, but she cites no instances. Harper (1929) experimentally infected twenty-five larvae of Culex pipiens with the Xiphidiocercaria, X.I., whilst Eckstein (1922) and Ruge (1903) record finding the encysted stage in mosquito larvae.

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. The development of exo-erythrocytic parasites of Plasmodium gallinaceum is more rapid and intense in chicks inoculated with blood from birds heavily infected with exo-erythrocytic parasites than in those inoculated with blood from birds in which no exo-erythrocytic parasites can be found.

2. If parasitized blood from a bird heavily infected with exo-erythrocytic parasites is inoculated intravenously into a normal bird and withdrawn 24 hr. later, it produces infections in normal birds characterized by a slow development of exo-erythrocytic parasites.

3. The proportion of birds which survived after inoculation with P. gallinaceum and daily treatment with suppressive doses of quinine, mepacrine or pamaquin, was greater when the inoculum was derived from donors in which no exo-erythrocytic parasites could be found (48%) than in those inoculated with blood from donors in which exo-erythrocytic parasites 'were numerous (15). No birds inoculated with parasitized blood from donors heavily infected with exo-erythrocytic parasites were sterilized of their infections by the action of the drugs, whereas in eleven out of sixty-six of the birds inoculated with parasitized blood from birds in which no exo-erythrocytic parasites could be found the infections were eradicated by the drugs.

4. Blood-inoculated infections of P. gallinaceum may in some cases be eradicated by short courses of treatment with mepacrine, quinine or pamaquin.

5. Whereas blood-inoculated infections of P. gallinaceum derived from donors in which no exo-erythrocytic parasites could be found were sometimes eradicated by prophylactic treatment with quinine, mepacrine or pamaquin, it was not possible to eradicate the infections by curative treatment with similar doses of these drugs.

6. The difference in type of infection produced by parasitized blood from birds in which no exo-erythrocytic parasites could be found at the time of withdrawal of the blood and those in which exo-erythrocytic parasites were plentiful appears to be due to the presence of exo-erythrocytic parasites in the circulating blood of the latter type of donor.

7. Sterilization by the action of quinine, mepa-crine or pamaquin of blood-inoculated infections from donors in which no exo-erythrocytic forms could be found, appears to depend upon whether the erythrocytic parasites are killed before they can become converted into exo-erythrocytic forms.

8. No evidence has been obtained of the intensification of development of exo-erythrocytic parasites by the suppression of erythrocytic parasites with drugs.

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.

Acquired resistance to paludrine in Plasmodium gallinaceum was retained undiminished after passage at frequent intervals through untreated chicks for more than 1 year.

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.

1. A thirty-two-fold increase in resistance to sulphadiazine has been induced in Plasmodium gallinaceum in chicks by treatment with that drug.

2. No loss in resistance to sulphadiazine occurred in the resistant strain during cyclical passage through Aëdes aegypti.

3. The sulphadiazine-resistant strain was resistant also to sulphathiazole, sulphanilamide and sulphapyridine, but not to mepacrine, quinine or pamaquin. An increase in sensitivity to pamaquin was observed.

4. The sulphadiazine-resistant strain was resistant to paludrine and its methyl homologue M 4430.

5. In strains maintained in a state of acute infection and treated with sulphadiazine, resistance to paludrine developed more rapidly than resistance to sulphadiazine, and in one strain a high degree of resistance to paludrine was obtained before any increase in resistance to sulphadiazine could be detected.

6. Resistance to paludrine as induced by sulphadiazine, develops rapidly and extends at once over the full range of doses which the chick will tolerate, whereas resistance to paludrine as induced by that drug itself, develops more slowly and by stages.

7. Whereas resistance to paludrine is induced readily by treatment with sulphadiazine, resistance to sulphadiazine is induced by paludrine only after treatment with high doses of the drug for a prolonged period.

8. In latent infections of Plasmodium gallinaceum resistance to paludrine or sulphadiazine was not induced by sulphadiazine during the period of the experiment (49–75 days), though the aggregate dosage of drug used was much greater than that with which resistance was induced in strains maintained in an acute state.

9. It is not considered probable that cross-resistance between sulphadiazine and paludrine is due to a similar mode of action of these drugs, as whereas sulphadiazine is antagonized by p-amino-benzoic acid paludrine is not.

1. Resistance to sulphanilamide, of a low order, has been developed in a strain of Plasmodium gallinaceum by the treatment of patent infections with the drug.

2. The sulphanilamide-resistant strain was resistant to paludrine over the whole range of doses tolerated by the host; it also proved to be resistant to sulphathiazole, sulphapyridine and sulpha-diazine, though the degree of resistance shown was much slighter than to paludrine.

3. Resistance to paludrine developed in the sulphanilamide-resistant strain before any resistance to sulphadiazine could be detected.