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The tick species commonly collected at the Northeast of Spain are reported in this paper. Data on hosts, temperature and humidity requirements, vegetation relationships, altitudinal distribution, and seasonal activity are included. R. sanguineus is commonly collected in areas with Mediterranean vegetation, esteppe, and semi- desertic esteppe, ranging from 190 to 1,000 meters above the sea level. R. sanguineus is related with sparse vegetal areas, and it is absent from areas with dense shrub or forests of every kind; sometimes, small populations may be collected in ecotones between Pinus spp. and esteppe formations. R. pusillus is closely related to areas of Mesomediterranean vegetation, sometimes subordinate to Pinus spp. and Quercus spp. The climate to which the species ally is always of continental type, with a hot and dry summer, and cold winter; although the species is commonly restricted to its main host, Oryctolagus cuniculus , several specimens have been collected from V. vulpes. Our data display the clear affinity of I. ricinus to the Supramediterranean vegetation (Aceri-Quercion faginae), places of Quercetum-Buxetum, as well as the Iberian Oromediterranean vegetation (Pinus sylvestris-Buxus sempervirens). Captures are scarce in forest of Fagus sylvatica , but data suggest that the species may be locally common on such places. Climate for the zones of collection of I. ricinus is Atlantic attenuated, with mild summers and humid winters. D. marginatus is strongly related to the xerophilic vegetation, widely spread through the Mediterranean, Supramediterranean, and hill levels, but does not colonize the true Oromediterranean vegetation. In our captures, the species is commonly collected in pubescent oak formations, but it does not penetrate in true forest associations. H. punctata breeds commonly on the Supramediterranean stage, clearly associated to Quercus spp., in wet areas. Both immature and adult stages of I. frontalis have been collected in areas of river vegetation (with hot and semi-dry summers, and mild winters, approx. 200 meters above the sea level) and in all the stages of the Mediterranean vegetation (meso-, supra- and oromediterranean). New host records are provided for both H. punctata and I. frontalis in Spain. Data are also reported for species scarcely collected, as H. hispanica, R. bursa, I. trianguliceps, and I. canisuga.

From January 1993 to June 1996, the epidemiology of myxomatosis and viral haemorrhagic disease (VHD) was studied in a free-living population of wild rabbits (Oryctolagus cuniculus ) in Spain by means of serological surveys and radiotracking. Myxomatosis was endemic and associated with the breeding period. Its serological pattern was characterised by a 100 per cent prevalence of antibodies in adult rabbits and a rapid increase in antibodies in young rabbits in their first year. No mortality from myxomatosis was detected in adults, and mortality in young rabbits could not be estimated because of interference by predators and scavengers and the deaths of many radiotagged rabbits inside their burrows. VHD was also an endemic disease associated with the breeding period. Adults had a higher prevalence of antibodies against VHD than young rabbits, teaching values of 80 to 90 per cent. During the study, there was an increase in rabbit numbers as a result of a decrease in mortality from predation which was associated with an increase in mortality due to VHD and in the prevalence of antibodies to VHD. Mortality from VHD was lower in rabbits with VHD antibodies than in seronegative rabbits, but some mortality from the disease was also detected in seropositive rabbits. The annual mean mortality rate due to VHD in adult rabbits was estimated to be 21.8 per cent., Funding was provided by the Dirección General de Medio Natural (Gobierno de Aragón) and a postdoctoral fellowship from CSIC-Junta de Andalucía (IFD97–2299) to C. C.

We looked for louse flies (Diptera, Hippoboscidae) in a mixed colony of 9 species of birds from 1991 to 1997. Alpine swifts (Apus melba) exhibited an unusually high prevalence (85.9%) by Crataerina melbae (Rondani, 1879). No birds from the other 8 breeding bird species were parasitized by this louse fly. We suggest that the number of potential swiftlike hosts as well as the size of hosts may account for the differential prevalence of the louse flies within the colony.