In a previous paper1 we gave an account of three non-furcocercous cercariae found in Bulinus contortus in the Sudan. During further investigations on the intermediate hosts of Bilharzia, other cercariae have been found in molluscs collected in different districts of the Sudan. As their post-larval development has not been studied, the classification of these cercariae has not been attempted; the procedure of giving them numbers rather than names, indicating specific peculiarities, has been continued.

In a previous paper concerning the numerous species of insect parasites associated with the Pine Shoot Moth, Rhyacionia buoliana Schiff., the mature larvae of the more important Hymenoptera were described in detail, special attention being paid to the mouth parts and tentorial structures which were found, in many cases, to provide valuable characters for distinguishing the species.

This paper contains a report on a collection of parasitic protozoa from the blood of some vertebrate animals of Uganda.

Seven new species and a number of parasites recorded for new hosts are described. New observations on some known parasites are also recorded.

An account is given of the life history of the crocodile haemogregarine. It is shown that the schizogony of Hepatozoon pettiti (nomen novum for Haemogregarina pettiti) occurs in the liver of the crocodile, while the sporogony takes place in Glossina palpalis, its intermediate host.

A list of all the blood parasites found, together with their hosts, is given.

Few records have been made of the process of fertilisation in the Digenea. Nicoll (1907) observed it in Podocotyle and states that it lasted but 10 min., and MacCallum (1913) has given an account of fertilisation in Microcotyle, one of the Monogenea.

Host and Record. A single female was found attached close to the left pelvic fin of a Histiophorus brevirostris Playfair caught off the south-west coast of Ceylon in January, 1932. One of the egg-strings was missing.

Orthopodomyia pulchripalpis was first recorded in Britain by MacGregor (1919), who found it, in association with Anopheles plumbeus Steph. and Aëdes geniculatus (Olivier), in a water-filled hole in a beech tree in Bpping Forest. He described it as a new species, 0. albionensis; but later Edwards (1922) showed it to be synonymous with 0. pulchripalpis Rond. Keilin (1927, 1927 a) found larvae of 0. pulchripalpis in a water-filled hole in a horse-chestnut tree in Cambridge, thus establishing a second locality for this mosquito in Britain. Beattie and Howland (1929) recorded it from water-filled holes in beech trees at Burnham Beeches, Buckinghamshire. In each case it was found in association with Anopheles plumbeus and Aëdes geniculatus.

Most of the new species herein described were collected by me from skins in the Transvaal Museum, Pretoria, for the loan of which I am deeply indebted to Mr Austin Roberts.

1. Entamoeba aulastomi and Hexamita sp. from Haemopis sanguisuga have been cultivated in inactivated horse-serum diluted 1 : 10 in 0·5 NaCl solution + solid sterile rice-starch, and upon an inspissated horse-serum slope covered with the liquid medium + sterile rice-starch. Cysts of E. aulastomi appeared on or after the 9th day from subcultivation, but cysts of Hexamita have not appeared in the cultures.

2. The amoeboid phase of E. aulastomi divides by a simple direct method, without the formation of a spindle. There is no equatorial plate. It was not possible to count the number of chromatin granules.

3. The mature cyst is quadrinucleate, though occasional octonucleate cysts are found. Chromatoids are present but are absorbed before hatching. A. large glycogen vacuole is present in the uninucleate cyst. The nucleus divides by the formation of a delicate spindle but no chromosomes were found.

4. E. aulastomi are not harmed by being kept at 2° C. but they die out in the 2nd subculture if kept at 30° C. and within 24 hours if kept at 37° C. The cysts also are killed at 37° C.

5. If treated with N/20 HCl all amoebae are killed in less than 10 min. but the cysts are unharmed.

Habitat and record: About forty specimens, of both sexes, collected and presented to me by Miss Miriam Rothschild from a bream Abramis brama (wt. 13 lb. 1 oz.) taken from the Tring reservoir, December, 1931.

1. Heat is an important factor in stimulating bed bugs to obtain food. Light and atmospheric humidity do not influence the reactions to heat to any great extent, but the state of nutrition and moulting do interfere with them.

2. The bug detects heat very slowly. At a room temperature of 23° C., from a distance of 4 cm., about 1½ min. were required before a bug reacted to the heat of the hand. At a lower temperature a longer period was required.

3. At ordinary room temperature a differential temperature of about 2° C. was necessary to cause a reaction to heat.

4. Bed bugs, although attracted to heat, will be repelled when the temperature is too high. Bugs were repelled by objects at 43° C. at a distance of about 3 cm.

5. Bed bugs have a sense of smell, but only react when very close to the odoriferous substance.

6. The odours of blood, muscle, subcutaneous tissue and clean, washed skin seemed to have no influence upon the bug; the odour of bile repels them; while liver at first attracted and then repelled them.

7. The odour of perspiration, depending upon its state of decomposition, sometimes repels and at others attracts bed bugs. Of the substances tested the odours of sebum and cerumen had the greatest attracting power.

8. The bed bug apparently discriminates between foods by taste.

9. Negative reactions to water counterbalance positive reactions to heat and odour.

10. The tendency to be in contact with an object, rather than the negative reaction to light, underlies the gregarious habit of the bed bugs as well as their search for places of retreat.

The hatching organ of Lipeurus columbae Linn. is described. It is very similar to that already described in sucking lice, and unlike that of any other group of insects. This resemblance is further evidence for the affinity of the Mallophaga and Siphunculata.

In Bufo vulgaris there is a small flagellate similar to species described from insects and the Brazilian cavy. Such flagellates were formerly placed in the genus Monocercomonas but the generic name has been amended to Retortamonas Grassi 1879 by Wenyon (1926). The toad flagellate which I name R. rotunda n.sp. differs in structure from Monocercomonas bufonis Dobell 1909, which Grassé (1926) has removed to the genus Tetramastix Alexeieff 1916.

1. Shortly before the imago emerges, air accumulates under the pupal skin. This air is swallowed by the imago and passes directly into the stomach; the resulting distention of the abdomen helping to push the thorax forward so as to rupture the pupal skin.

2. After rupture of the pupal skin, the imago continues to swallow air, which causes the stomach (and therefore the abdomen) to expand further and thereby facilitate the emergence of the imago.

3. Within an hour after complete emergence of the imago, the air in the mid-gut commences to pass forward into the (hitherto empty) oesophageal diverticula, and after 12–22 hours the mid-gut no longer contains air. (Note. We find that the process of emergence here described for Culicidae also applies to some other diptera which, like mosquitoes, live for a part of their lives in water.)

4. In mosquitoes fed on liquid (e.g. raisin juice) other than blood, the liquid goes direct into the oesophageal diverticula and displaces the air from them more or less completely (the experiments of Nuttall and Shipley (1903, p. 177) showed the air to be thus displaced, but this point was not specially mentioned by them).

5. When mosquitoes feed on blood (whether previously fed on raisin juice or not) all the blood goes direct into the mid-gut. (Note. Traces of blood, negligible in quantity but sufficient to cause visible coloration, are occasionally to be observed in the diverticula. This appears more likely to happen in cases where no previous meal of raisin juice has been taken.)

6. When a mosquito is fed on raisin juice and subsequently starved for a few days, the fluid contents of the diverticula are entirely replaced by air. The experiments indicate that this air reaches the diverticula via the cardia, in the same manner as during their initial inflation.

7. In the case of “domestic” mosquitoes, the air in the diverticula becomes reduced in quantity (sometimes disappearing altogether) prior to hibernation, and increases in amount towards the end of the hibernating period.

8. In the case of male mosquitoes, the transference of air from the mid-gut to the oesophageal diverticula proceeds pari passu with the turning of the hypopygium, the two processes terminating at about the same time.

Host and Record. At least four specimens of the parasite were found attached to the sides and belly of a sail-fish Histiophorus gladius Day caught off the south coast of Ceylon. I was fortunate enough to obtain two of these, both females, complete except for the egg strings. They measured 135 mm. and 157 mm. in their total lengths. One of them, the smaller, is illustrated in Fig. 1.

Male unknown.

Female (Fig. 1): Scutum (2·2 x 1·8 mm.) much longer than broad, with well-marked lateral folds on the anterior half; cervical grooves rather far apart at origin, then faint and divergent; some very fine punctations on the lateral folds and in the area between them and the cervical grooves, the posterior region very glossy and almost devoid of punctations. Emargination very slight. Venter: vulva between coxae IV. Genital grooves only slightly divergent, not extending beyond the anus. Anal groove horseshoe-shaped, then shallow and divergent. Spiracles nearly circular and very large (larger than coxa IV). Capitulum long; basis triangular, without cornua or auriculae, its ventral surface divided by a transverse line. Porose areas large, sub-rectangular, with narrow interval. Palps fairly stout; hypostome lanceolate, dentition 2/2, about twelve teeth per file, the outer the stronger. Legs: coxa I deeply cleft into two equal flat teeth, recalling that of Rhipicephalus, and very unusual in Ixodes; coxae II–IV with an external tooth, diminishing in size. Tarsi long (especially tarsus I) and tapering, the pad nearly as long as the rather weak claws.

The cestode herein described was obtained from the intestine of a Schokari Sand Snake which died on 16. xii. 1929 at the Zoological Gardens, Giza, after being 6 months in captivity. The material (Museum No. 1717) was placed at my disposal by Prof. Khalil for study in the Department of Parasitology.

Life history of Ixodes ricinus.

1. Under laboratory conditions, at 60–70° F. the pre-oviposition period was usually found to last 15–22 days.

2. Eggs began to hatch after about 4 weeks at 60–70° F. and after 37 weeks at 50–60° F. in the laboratory.

3. Unfed larvae placed on a hedgehog mostly dropped off gorged in 88–120 hours (shortest feeding period 67½ hours). Larvae gorged on sheep in 65 hours.

4. From larvae gorged in August and kept in the laboratory, nymphs emerged after 6–7 weeks. From larvae gorged in September and October, nymphs emerged after 28–37 weeks.

5. Unfed nymphs gorged in 4–7 days, mostly in 5 days.

6. From nymphs gorged on sheep in spring and summer, and kept in the laboratory at 60–70° F., adults emerged after 10–19 weeks.

7. Females gorged on sheep in 7–11 days, mostly in 8–9 days.

8. Sex ratio: about 5: 9 (basis: 362 males and 671 females emerged from nymphs in the laboratory).

9. Longevity unfed: males and females survived 21 months; one male survived for 31 months in the laboratory. Larvae survived 2 years; some were able to feed after fasting 15 months, and nymphs after fasting 13 months.

Bionomics.

10. Hosts: one or more stages of I. ricinus have been found on the following hosts. Mammals: horse, dog, fox, hedgehog, hare, rabbit, stoat. Birds: hoodie-crow, rook, jackdaw, starling, golden plover, barn owl, kestrel hawk, and merlin hawk.

11. When Blackface and Cheviot sheep were kept on the same pastures in spring, the former became more heavily infested with ticks than the latter. It is said by shepherds that ewes weakened by lambing are more liable to infestation than strong barren ewes. Comparative counts of the infestations of a barren ewe and two ewes with lamb appear to confirm the shepherds' view. Non-acclimatised (experimental) sheep, when exposed on a tick infested farm, rapidly. lost condition at first, and subsequently began to recover. When these sheep, whose health and general condition were low, were compared with native sheep their average infestation with ticks was found to be higher than that of the natives. As the health and weight of the experimental sheep improved, the average infestations of these and of the native stock approximated.

12. Reports on the geographical distribution of I. ricinus in various districts in Scotland, received from sheep farmers and others, are recorded.

13. There is a distinct seasonal periodicity in the activity of I. ricinus. It appeared on sheep early in March, and became increasingly numerous during April-May. In June the numbers began to decrease, and steadily diminished until late August, when there occurred a slight increase in average infestation of sheep. This increase was of short duration and by the middle of November no ticks were found on sheep. The same periodicity was observed in the following spring and summer. An occasional tick was found on sheep during the winter, in mild warm weather. Adult ticks first appeared in early March. Nymphs appeared by the middle of March. Larvae were apparently most numerous in May–June.

14. The seasonal incidence of I. ricinus on sheep in 1930 bore no apparent relation to rainfall.

15. When the variations in average weekly air temperature for 1930–31 are charted in relation to the seasonal incidence of ticks on sheep for that period and the curves compared, there seems to be a correlation between temperature and tick activity. The data indicate that the tick infests sheep in the greatest numbers at 45–60° F. The lower critical temperature for tick activity in nature appears to be 40–45° F., and the higher 60–70° F.

16. Over a thousand gorged nymphs and many larvae have been collected in the field and bred out in the laboratory; in none of them has there been any evidence of hyperparasitism.

It has been determined that anaplasmosis may be transmitted by Dernmcentor andersoni under the following conditions: (1) Larvae may acquire the infection by engorging on a bovine whose blood contains anaplasms and may transmit the infection as nymphs to susceptible bovines; and (2) in a similar manner the nymphs may acquire the infection and transmit it as adults. The test of “hereditary” transmission was negative, i.e. the larvae did not apparently acquire the infection from adult females which engorged on carriers of anaplasmosis. Conditions of transmission by D. andersoni are the same as those which have thus far been determined by me for D. variabilis. The incrimination of these two species of tick points to the possibility that anaplasmosis occurring anywhere within the known range of distribution of that disease in the United States may be tick-borne so far as a coincident distribution of known tick carriers can establish this possibility.

Alexeieff (1911) described two trichomonads from the horse-leech Haemopis sanguisuga:Tetratrichomonas prowazeki and Trichomonas sanguisugae. T. prowazeki is characterised by its four anterior flagella of unequal length and its poorly developed axostyle. The feature which he considered to be of specific value in T. sanguisugae is the “chapelet de grains” in place of the basal fibre.

The accurate identification of cestodarian and cestodan helminths depends so much upon the correct interpretation of their internal morphological features that a rapid yet satisfactory routine technique in their preparation for microscopical examination is much to be desired. Not all workers publish their technical methods, and, among those who do, no two seem to be in agreement. Some of the collection and preservation methods, in particular, which are advocated, whilst admirable for museum specimens or histological study, are impracticable under the conditions of a field survey, where many host animals have to be quickly examined and rapidly accumulating specimens are preserved and studied by methods which will not strain unduly the limited facilities of a field laboratory or a small biological station.