Larval macrodistribution of cytotypes of the Simulium venustum/verecundum complex among 60 stream sites over a limited geographic area (Avalon Peninsula, Newfoundland) was investigated. Cytotypes included EFG/C, ACD, AA AC(gb), and CC2-3 (combined CC2 and CC3). Stream sites were classified into four types: outlets, trickles, small streams, and large streams. Factors that might explain patterns of occurrence (presence or absence) were examined using correlation, frequency, and cluster analyses. The data showed that larval EFG/C and ACD dominated outlet sites. The CC2-3 and AC(gb) cytotypes were most frequent at downstream sites. In downstream locations CC2-3 was found at almost all sites, whereas AC(gb) was most frequently found in cool, canopied streams, where the bottom consisted mainly of small stones and rubble. In the spring AA was most common at outlet sites. In the summer AA was most frequently found at outlets and trickles. The summer generation(s) of AA was associated with the distribution of trailing and emergent vegetation.

Data are presented from laboratory experiments to show the effect on the life history of Simulium vittatum and the S. verecundum complex of reducing available food supply. These experiments showed that development time was extended, survival declined, size decreased, and fecundity markedly reduced when food supply was reduced beyond a certain level. Differences between the two species may have an ecological basis. It is argued that such effects occur in natural populations of simuliids and that they have implications for studies of vectors and their control.

A study of the pre-imaginal simuliid fauna of South-East Queensland was conducted to elucidate some of the aspects of their ecology . A total of 17 species of three genera (Cnephia, Austrosimulium and Simulium) bred in the area . The highest diversity of species was found to occur in mountainous areas near the coast which had the following conditions : high rainfall, steep relief, cool temperatures, on the edge of forests with streams of the order 1-3 (using a 1 : 250,000 map) .More detailed studies of A . bancrofti, S. nicholsoni and S. ornatipes were made to investigate microdistribution, colonization, drift, pupation timing and population changes . Current velocity was the most important factor determining the distribution of A . bancrofti, while the distribution of S. nicholsoni was influenced by a preference for vegetation substrate and current velocity . Late instar larvae of A . bancrofti and S. ornatipes occurred in faster currents than early instar larvae . Pupae of these two species primarily occurred on the downstream side of submerged substrates . Colonization of a particular stream was dependent on the oviposition preference of gravid females while drift, looping, or descent on silk threads was used for larval dispersal from the oviposition site. Early instars of A . bancrofti drifted from quiet reaches of mature rivers to rapids, while S. ornatipes larvae appeared to be more sessile with limited dispersal from site of egg masses . Drift occurred throughout 24 hours with little change in total numbers . Early instars of A . bancrofti however showed a definite diurnal tendency while the proportion of late instars increased at night . Pupation of S. ornatipes was diurnal under undisturbed conditions . The larvae of A . bancrofti and S. nicholsoni both developed in the Brisbane River system, however the populations of A . bancrofti peaked in late winter, a dry season with stable water conditions while S . nicholsoni larvae were most abundant from late summer, at the end of the rains to the early winter . The larvae of S. ornatipes, which occur in small streams down to temporary trickles, were most numerous during the warm rainy period .Dr. W. Junk b. v . Publishers -The Hague, The Netherlands

The seasonal activity of the adults of 13 tick species was studied on cattle herds in the Central Province of Zambia from 1969 to 1972. The six main species, Boophilus decoloratus (Koch), Hyalomma marginatum rufipes Koch, H. truncatum Koch, Amblyomma variegatum (F.), Rhipicephalus appendiculatus Neum., and R. evertsi Neum. behaved as previously described for the Southern Province. R. compositus Neum. appeared from August, with peak numbers in September-October. R. simus Koch and R. tricuspis Don. appeared from October, for seven months and three months respectively. R. supertritus Neum. and Ixodes cavipalpus Nutt. & Warb. had a brief activity season from November to January, and R. pravus gp. and R. sanguineus gp. were active from December to July. The distribution of ticks over the body of cattle was determined by fractionised collections, which gave reliable quantitative information for nine of the species. A limited number of collections from sheep, goats and dogs are analysed in relation to season. Collections from 127 wild animals, mainly along the escarpment and riverine bush of the Zambesi, are recorded.

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