Sexual behaviour of Lepthyphantes leprosus (Ohlert) (Araneida, Linyphiidae), with notes on the function of the genital organs

INTRODUCTION The Linyphiidae are builders of horizontal webs, on the underside of which the animals live. In most species the reproductive period is limited to a few weeks ; after that time males are rarely met with. As in consequence all observations should be made in the course of a few weeks the species of this family are not very suited for the purpose of a lengthened and thorough investigation into the sexual behaviour. Tretzel (1954), however, observed the perennial occurrence of adult specimens of Lepthyphantes leprosus (Ohlert). Locket & Millidge (1953) and Wiehle (1956) likewise mentioned this phenomenon. The species moreover was known to occur in large quantities in the southern part of the Netherlands, viz., in the artificial marl-caves of the Kannerberg near Maastricht in the province of Limburg, particularly in the parts used by the local population for storing agricultural products. These qualities made Lepthyphantes leprosus an attractive test object. Most test-animals were collected from the caves in the subadult stage, which enabled me to work with virginal specimens. All animals were kept individually in glass-cages or glass-tubes. For the purpose of observing the sexual behaviour a male was introduced into the cage of a female. Observations were facilitated by the use of a binocular microscope with low magnification. The conditions, under which the animals were kept and observations were carried out, resembled those of the caves as nearly as possible : a temperature of 10°C and a high relative humidity. Although the caves are dark, a small light was used to make observations possible.