This paper reports initial data on genetic variability and genetic divergence in five populations of two cave dwelling orthopterans, genus Troglophilus. Most of the present literature concerning electrophoretic variation of cavernicoles reports low levels of genetic variability, e.g., cave populations of fishes (Avise and Selander, 1972), millipedes (Laing et al., 1976a), leiodid beetles (Laing et al., 1976b) and spiders (Johnston and Carmody, 1977). However several recent reports (Sbordoni et al., 1976a, 1978, 1979, 1980a, 1980b; Giuseffi et al., 1978; Dickson et al., 1979; Sbordoni, 1980) and additional unpublished data from our own genetical analyses on different cavernicolous animals, indicate that troglophilic and troglobitic populations of aquatic and terrestrial invertebrates subjected to long term cave isolation may display levels of genetic variability comparable to, or even higher than, the levels observed in non-cave invertebrates (Powell, 1975; Selander, 1976). As far as cave crickets (Rhaphidophoridae) are concerned, Cockley et al. (1977) report low variability in the camelback cave cricket Ceuthophilus gracilipes from Pennsylvania, with heterozygosity values ranging, in different populations, from 0.020 to 0.033. In contrast to these results our preliminary data on Dolichopoda geniculata (Cobolli Sbordoni et al., 1974; Sbordoni et al., 1976b) and a further extensive study of 23 populations belonging to five species of Dolichopoda from Central Italy indicate a fairly high degree of variability, with levels of heterozygosity ranging from 0.113 to 0.280 (Sbordoni et al., unpubl.). Mediterranean Troglophilus cave crickets are similar to American Ceuthophilus. Both are Rhaphidophoridae and even if not closely related (Hubbell and Norton, 1978), occupy parallel niches in the two continents, most of the species being adapted to the twilight zones of caves, feeding on living arthropods, guano and chlorophyllan plants, sometimes outside caves (Remy, 1931; Vandel, 1964). The range of the genus Troglophilus extends from Anatolia to Lombardy including Greece, Yugoslavia and Austria. In Italy this genus shows a disjunct distribution: two species, T. cavicola (Kollar) and T. neglectus Krauss, are limited to limestone areas along the foothills of the Alps in northern Italy, from Friuli west to pre-alpine Lombardy, namely the Lake Como region, where marginal parthenogenetic populations of T. cavicola occur (Capra, 1951; Baccetti, 1961). A third species, T. andreinii Capra, is present in Apulia where two subspecies have been identified: T. andreinii andreinii, which is widespread in caves of northwestern Apulia, and T. andreinii hydruntinus La Greca, confined to the southern edge of the Salentine Peninsula (Baccetti and Capra, 1969). We investigated the patterns of genetic variability in five Troglophilus populations, two belonging to T. cavicola from northern Italy, and three belonging to T. andreinii from Apulia. We attempted to evaluate 1) levels of heterozygosity in Troglophilus to compare them with both Ceuthophilus and Dolichopoda and 2) the degree of genetic divergence between populations and species. The populations