1. Six species of Amitermes, one from Panama and five from California, have been examined for protozoa. Certain protozoa have been found in many or all individuals examined of all species, but they are much less abundant than are flagellates in termites of the three xylophagous families below the Termitidae.

2. Trichomonas lighti n.sp. has been found in all species, but not in all individuals.

3. Chilomastix minuta n.sp. occurs in Amitermes beaumonti.

4. Embadomonas termitis n.sp. is described from Amitermes beaumonti.

5. Endamoeba beaumonti n.sp. has been observed in five host species. In its size and nuclear structure it resembles Endamoeba disparata of Mirotermes hispaniolae.

6. Nyctotherus silvestrianus n.sp. has been found in three of the Californian species. It resembles N. termitis and N. ovalis, but is larger than the former and smaller than the latter. A long filament is attached to the end of the cytopharynx. A thickened, V-shaped structure lies against the cyto-pharynx. Several deeply staining fibrils arise from this V.

7. A coccidian has been found in one individual of Amitermes minimus. This forms sixteen banana-formed merozoites and three sporoblasts as in Chagasella.

8. Micro-organisms other than protozoa are very abundant in the intestines of all six species of Amitermes, and they are similar in all.

It is often desirable that a mid-gut showing oocysts be preserved for demonstration purposes or for record. The method herein described seems to have certain advantages over those usually recommended in saving considerable time during fixation, staining and mounting of the specimen, also in permitting pigment within oocysts being seen on any part of the mid-gut. The stain used (toluidine blue) is not taken up to any great extent by the nuclei of the gut cells, but appears to have some degree of selective action on the younger oocysts.

Five larval trematodes have been obtained from a search of many terrestrial molluscs. All are distome cercariae developing in sporocysts. One species appears to be Cercariaeum helicis Braun the sporocyst and cercaria stages of which are described here in detail. The other four species are new. Cercaria politae lucidae n.sp. and C. lauriae cylindraceae n.sp. the two Xiphidiocercariae described are rare in this locality, each species being found only on two occasions. The larvae obtained are also less abundant and less representative of the larval Trematode groups than those met with during my search of the local fresh-water molluscs for similar parasites (Harper, 1929, 1931).

During the investigation two new records have been added to the molluscan fauna of Forfarshire (Vice county, No. 90), viz. Polita lucida Drap., and Succinea elegans Risso. No helminth parasites were found in the last-named mollusc.

Description. Body more or less elongated, narrowing anteriorly and posteriorly. Length 1·34–1·441, maximum width 0·476, maximum thickness 0·433, both measured in the region of adhesive apparatus. Entire surface of the body, except adhesive apparatus and the region posterior to second testis, covered with fine spines. Ventral folds originate approximately at centre of body and meet a little behind the level of posterior third to form a shallow cavity occupied by the adhesive apparatus. Adhesive apparatus smooth, oval, 0·4–0–44 long, 0·26–0–3 wide, with narrow central depression, anteriorly reaching acetabulum and posteriorly anterior margin of posterior testis. In it are imbedded vitelline follicles, anterior testis, ovary and anterior portions of cirrus sac and uterus.

Seven species of cercariae and four of metacercariae collected at Roscoff, Finistère, during August, 1931, are described. They have been referred to appropriate systematic groups and wherever possible, probabilities concerning life histories are suggested. Four of the cercariae and two of the metacercariae are recorded as new to science.

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.

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.

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.

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.

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.

1. An account is given of the development of strains of Trypanosom gambiense in Glossina tachinoides.

Complete development with infection of salivary glands and hypopharynx occupies from 12 to 40 days and upwards, according to the strain of trypanosome used and the temperature conditions during development.

2. It is shown that the first or intestinal phase of development is passed within the extra-peritrophic space and that the lumen or intra-peritrophic space of the gut is not involved.

3. The importance of the proventricular infection as an index of maturing infections is stressed, and it is shown that filamentar crithidia are always present in this organ in the later stages of infection when infection of salivary glands is taking place. It has been proved that these filamentar crithidia may constitute up to 20 per cent. of flagellates in the proventriculus and are partly responsible for the further migration to the salivary glands.

4. An account is given of the infectivity to G. tachinoides of twenty-six strains of T. gambiense from epidemic and endemic sleeping sickness areas in Northern Nigeria. None of the twenty-six was proved to be non-transmissible and twenty-five of the strains gave Total Infectivity Rates in the tsetse of from 0·9–10·5, the Cyclical Developmental Rates ranging from 0·6–9·8.

5. No evidence has been obtained that strains of T. gambiense from chronic cases of human trypanosomiasis in endemic areas are less transmissible by tsetse than strains originating in epidemic areas.

6. An account is given of experiments in which G. tachinoides infected with T. gambiense were exposed to 37° C. for varying lengths of time. The effect of high temperature during the infecting period is seen in a marked and constant increase in the proportion of tsetse infected. In the case of one strain a total infection rate of 77·8 per cent. was obtained with true cyclical development in 73·5 per cent. of the tsetse used.

7. It is suggested that the temperatures at which experimental tsetse are infected in the laboratory with T. gambiense are excessively low, and an investigation is to be made into the optimum climatic conditions for development of the trypanosome in the fly with a parallel attempt to correlate this with the climatic conditions under which wild tsetse become infected in nature.

A method is described by which individual bed-bugs, weighing only 5 mg., can be accurately weighed, and their rate of loss of weight measured during starvation.

Fasting bed-bugs were kept for various periods at five temperatures, ranging from 8° C. to 37° C., and at four humidities—0, 30, 60 and 90 per cent. relative humidity—at each temperature. Analysis after the experiments showed that the same amounts of food reserves were used up at each humidity for one temperature, and, as more water was evaporated from those kept in dry air than from those in moist, the proportion of dry matter rose most rapidly in dry air. Protein was the main food reserve used.

Although the rate of loss of water was greatest in dry air, the rate of loss was relatively greater in moist air when the saturation deficiencies are compared. It appears that the insects conserve their water in dry air, but their surface area being so great in comparison with their volume, they cannot prevent all evaporation. This evaporation is at a rate nearly proportional to the saturation deficiency of the air.

In moist air water appears to be evaporated freely. It is suggested that the spiracles are kept closed more in dry air and less in moist, which accounts for the fact that the rate of evaporation is proportionately greatest in moist air.

A comparison is made between the results obtained with Cimex and Rhodnius.

1. The paper describes an experimental study on the effect of atmospheric humidity upon Rhadnius. The work was carried out on fasting males of known age, kept at 23° C. at different relative humidities; the proportion of water was determined after the lapse of definite periods of time. The normal male contains 30 per cent. of dry matter.

2. Taking the results after 42 days' starvation, at 30, 60 and 90 per cent. humidity, the weight of each group of bugs has fallen to 50 per cent. of what it was at the start of the experiment. Those kept in damp air have lost dry matter and water in the same proportion, so that the percentage of dry matter after starvation is still 30 per cent. of the total weight. Those kept in drier air lose more water but oxidise less dry material, so that the proportion of solids rises during starvation: in those kept at 30 per cent. relative humidity the proportion of solids rises to 39 per cent. The figures for insects kept at 0 per cent. humidity are consistent, but it is not possible to obtain them beyond the 32nd day.

3. Death is probably due to a rise in the concentration of the body fluid and not to the exhaustion of food material. This is shown by the fact that the exhaustion of solid matter is actually less in dry air than in moist, though mortality is only observed among the bugs kept in dry air.

It has already been shown (Imms, 1930) that the stem generation of the frit-fly in the Harpenden district is subjected to natural destruction, to a marked degree, by the agency of certain hymenopterous parasites. Among these, two species, viz. the Cynipid Rhoptromeris eucera Htg. and the Chalcid Halticoptera fuscicornis (Walk.) were found to predominate in numbers. Parasitisation, to a lower degree, by the Proctotrypid Loxotropa tritoma Thoms. was also noted and the Chalcid Callitula bicolor Spin. was recorded for the first time as having been reared from this same host. Evidence was also brought forward which o appeared to indicate that the parasitisation of frit-fly by the above combination of species increases in intensity as the season advances. In other words the stem generation of frit-fly, attacking late sown oats, is subjected to markedly heavier parasitisation than when it attacks oat sown earlier in the same season.

In a recent paper (Parasitology, 23, No. 4, 492) I described under the name Microcotyle sciaenae a new species of Microcotyle from the gills of Sciaena antarctica. Dr M. C. Hall, Chief of the Bureau of Animal Industry, Washington, D.C., has kindly pointed out to me that this name is preoccupied by M. sciaenae Goto (1894). I now propose the name M. sciaenicola in place of this homonym.