Description of the male and first-stage juvenile of Longidorus intermedius Kozlowska & Seinhorst, 1979 (Nematoda: Dorylaimida), and notes on its morphology and distribution.

Longidorus intermedius Kozlowska & Seinhorst, 1979 is redescribed from specimens recovered from oak (Quercus L.) forests in Bulgaria. The male and the first-stage juvenile were recorded for the first time, as were populations from Macedonia and Turkey. L. intermedius is identified here as the first species in the genus with only three juvenile stages and a pan-European distribution. The species was recovered from 36 of 46 oak forests in Bulgaria, found associated with each of nine oak species sampled and reached population densities of up to 289 specimens per 200 cm(3) of soil. The distribution of L. intermedius in Bulgaria, and in other countries, suggests that this species, like Xenocriconemella macrodora (Taylor, 1936) and probably L. aetnaeus Lamberti, Agostinelli & Vinciguerra, 1986, can be used as an ecological indicator for habitats where Quercus associations represent a primary vegetation type.