Infective larvae of Dirofilaria immitis commonly escaped from the tips of the Iabella and rarely from the mid-portion of the labium of Aedes aegypti as they engorged blood or just probed on mice. During the infective feed a small quantity of liquid, not more than 1 µI in volume, accumulated around the emerging larvae. Liquid was never seen when uninfected mosquitoes engorged on mice. This fluid is of insect origin and probably haemolymph that exuded from the lumina of the labella or labium during worm emergence. The presence of the fluid prevents dessication of larvae on the surface of the skin and maintains them in a liquid medium until they enter the puncture wound that remains after withdrawal of the biting fascicle. The possible effects of the fluid on the geographical distribution of mosquito borne filariae are discussed.

Batches of 10 Anisakis larvae from Greenland salmon (Salmo salar) were labelled with radioiodcin and fed to 10 haddock (Melanogrammus aegiefimis). Similar batches of larvae from herring (Clupea harengus) were fed to 8 whiting (Merlangius merlangus). At post-mortem from 15 to 190 hours after infection, 0 to 6 larvae were recovered from whiting (over-all recovery rate 18.8%) and 0 to 4 larvae were recovered from haddock (over-all recovery rate 27%). Larvae penetrated the wall of the stomach or of a pyloric caecum. They were first seen in the body-cavity 24 hours after infection and a delicate capsule was present around some of them by 34 hours. Most larvae were recovered from the body-cavity but, in haddock, two had penetrated the epaxial musculature.

Autoradiographs revealed that sporocysts of Cercaria helvetica XII and rediae of Sphaeridiotrema globulus, incubated in a medium containing [14C]-glucose, exhibited slight radioactivity in their body wall after only 30 seconds incubation. Activity in sporocysts and rcdiae gradually increased as the incubation period was extended until after 4 minutes, a heavy reaction was observed in the parasite body wall as well as in the germ balls and developing cercariae within the parasite brood chambers. The redial caecum appeared to incorporate the labelled compound much more intensely than did the redial body wall.

When uninfected Bithynia tentaculata, as well as B. tentaculata infected with either S. globulus or C. helvetica XII, were maintained in pond water containing [14C]-glucose, activity could be detected in the gills of both infected and uninfected snails after 5 hours incubation. After 12 hours a much heavier labelling was apparent in the gills, together with moderate activity in the haemocoelic spaces, foot musculature, stomach wall, and gut contents. After 20 hours a more intense labelling was apparent in these regions of the snail body and, in addition, some activity could be detected in the digestive gjand tubules of the host and, in infected snails, in the bodies of developing parasites. After 30 hours incubation the labelled compound had become incorporated into most of the host tissues but was most intense in the digestive gland tubules. Heavy activity was also evident in the parasites at this stage although certain cystogenous gland cells of the cercariae of both parasite species did not incorporate the labelled compound.

Two new species of helminths, Fastigiuris prudhoei from Ochotona rufescens Gray, 1842, and Trichuris mofidii from Rhombomys opimus Lichtenstein, 1823, have been identified and described from mammals collected in Iran.

The morphology of Diplostomulum (Tylodelphylus) xenopodis Southwell and Kirshner, a strigeatoid metacercaria from the pericardial cavity of the African clawed toad, Xenopus laevis, is described and its systematic position discussed. The parasite has both a high incidence and intensity of infection in host samples from the Cape: 60% of 410 X. laevis examined carried D.(T) xenopodis and 26% of infected hosts harboured 100 worms or more. Parasite longevity in excess of 3 1/2 years was recorded in laboratory maintained toads and the effects of experimentation on the host are considered particularly in relation to parasite survival and pathogcnicity. Attempted maturation of the metacercariae in Anas and Larus species was unsuccessful; aspects of the biology of transmission of the parasite in the natural habitat are discussed.

Five Macaca mulatta were each inoculated with 200 larvae of Brugia pahangi. One monkey showed no microfilariae and the other 4 only low and transient microfilaraemias. Another group of 5 monkeys were each given an original 200 larvae and 11 further infections with 50 larvae but no better microfilaraemias were obtained. These monkeys were killed between 176 and 185 days later and no adult worms could be found. A few adult worms were found in two further monkeys killed 60 days after infection.

Brugia pahangi infects mammalian hosts of several orders but the only primate found naturally infected is Nycticebiis coucang (Laing et al., 1960, Ash and Riley, 1970). Edeson et al. (1960) tried to infect Macaca inis, M. nemestrina, M. mulatta and N. coucang but were only able to detect microfilariae in N. coucang. On the other hand, B. malayi (sub-periodic strain) infects primates much more readily (Laing et al., 1960) in nature. Fredericks and Ramachandran (1968) successfully infected 26 of 27 M. mulatta with B. malayi.

The life-cycle of the cestode Proteocephalus percae (Müller), a parasite of the perch Perca fluviatilis L., involves two hosts and was studied both experimentally and by field observations in Hanningfield Reservoir, Essex. The hexacanth embryo is bilaterally symmetrical, with three pairs of hooks and paired glands. The copepods Cyclops (Eucyclops) agilis, C. (Mesocyclops) leuckarti and C. (Acantftocyclops) viridis were infected experimentally with P. percae eggs. The egg hatches in the intestine, the embryo penetrates the intestinal wall by means of its hooks and possibly by secretions from its paired glands, and the larva develops within the haemocoel. Development took 3–4 weeks at 14°C in C. viridis, but the rate of development varied at different temperatures and copepod species differed in their suitability as hosts for P. percae larvae. The adult cestode showed a yearly cycle of occurrence and maturation in perch. Egg production occurred in the spring, after which adult worms were lost from the fish to be quickly replaced by juvenile worms of the succeeding generation. Increase in length of the adult cestode population occurred in two stages, a period of rapid initial growth commencing immediately after establishment in the perch, and a second stage closely associated with maturation of the worms.

Culicoides nubeculosus, the vector of Onchocerca cervicalis, was found to have two daily peaks of activity when attacking horses in South Hertfordshire. The evening peak occurred just before sunset and was 2–2.5 times as great as the morning peak. Most of the attacking midges (85 %) landed on the ventral mid-line of the horse in an area stretching from the front legs to the sheath or mammae. The attractiveness of the ventral surface of the host was found to be related to illumination and to the arrangement of the host's body hair. 42.1 % of the C. nubeculosus landing on the host were successful in obtaining a blood meal.

An immature parafilarial worm recovered from the anterior chamber of the eye of a buffalo (Bubalus bubalis) is described. On the basis of characteristic cuticular ornamentation at the anterior extremity, an undivided short oesophagus and unequal spicules, the specimen has been identified tentatively as a male juvenile of Parafilaria bovicola. This is the first record for P. bovicola as an accidental infection of the eye of a buffalo.

Adults of Hepatojarakus malayae live in the bile duct of many species of Rattus in Peninsular Malaysia, ine life cycle of this parasite was studied in laboratory white rats. Eggs were passed out with the faeces at the early morula stage and hatched within 15 hours, giving rise to the first stage larvae. These developed to the third stage in about 36 hours and these were given orally to new rats in experimental infections. The migratory route of the larvae from the gut to the liver was traced. Penetration into the host appeared to be confined mainly to the fundic wall of the stomach. The larvae presumably followed the portal route to the uver. Here the final moult occurred before the young adults moved into the biliary passages.