Studies on gastropod mating are important for understanding various taxonomic and ecological problems. Field observations on the copulation of Arion lusitanicus Mab. revealed four phases: recognition of the partners, courtship dance, copulation and spermatophore transfer, separation and parting of the partners; the slug behaviour during these phases and their duration are described.

The Occurrence and Sex Ratio of Diabrotica virgifera Le Conte Beetles on Sweet Maize (Zea mays var. Saccharata) In South-Eastern Poland Near Rzeszów in 2007-2009 Studies were conducted in 2007-2009 on sweet maize (Zea mays var. saccharata), Candle variety, in Terliczka near Rzeszów. The observations were carried out based on an permission from the Main Inspectorate of Plant Health and Seed Inspection, No. WF-411d/5/2008. The objective of the conducted study was to specify the occurrence dynamics of Western corn rootworm (WCR) (Diabrotica virgifera) beetles on sweet maize in order to establish the optimal period for their control. In addition their sexual structure between July and September were specified. In south-eastern Poland D. virgifera beetles began their flights onto sweet maize plants from the second decade of July. Male occurred first, and the flights of females began several days later. Moreover, it was found that the maximum number of males on plants is recorded earlier than that of females. During the feeding of beetles on maize the period of their most abundant occurrence was from the end of July to the third decade of August. During the flight of adult one population peak was usually recorded: in the third decade of July and the first decade of August, and only in 2007 was it in the second decade of July. In 2007-2009, D. virgifera ended their feeding in late September. Females dominated among the captured insects during the study years. Their percentage share in the total number of captured beetles was from 59.7 to 84.1%. The population of males in individual years varied, and their percentage share was between 15.9 and 40.3%.

A total of 5111 slug specimens of 8 species were caught in 1994-1996 in an urban habitat in Rzeszów (SE Poland), the most abundant being Arion rufus (L.). Other abundant species were: Arion fasciatus (Nilsson, 1822) Deroceras reticulatum (O. F. Müll.) and Limax maximus L. The abundance of slugs varied between the seasons and depended on weather conditions (rainfall, temperature, air humidity); reaction to frosty winters varied between species.

Arion lusitanicus Mab. has two peaks of abundance in the vegetation season. One falls on mid-May when immature individuals dominate in the slug population. The juveniles feed on young plants and grow rapidly. Another mass occurrence of the pest falls on August at the emergence stage of winter plants. The population density remains high during 4 to 6 weeks, almost till the end of September. Adult individuals are predominant in the slug population in late summer and autumn, whereas juveniles hatched from the eggs laid in August appear later.

Spermatophore formation and transfer in slugs are complex and still obscure. In the slug Arion lusitanicus Mab. the spermatophore is formed 30-35 minutes after atrium eversion; as long as the copulating slugs are connected, each spermatophore is partly in the donor's epiphallus and partly in the recipient's spermatheca duct; spermatozoa are released in the spermatheca duct 12-13 hrs after the spermatophore transfer; the spermatophore tunicle in the spermatheca dissolves within 48-72 hrs.