It is difficult to generalise about mite behaviour. Most are tiny creatures which either crawl or run through soil and leaf litter, or in other habitats. Others are rather sedentary. Some mites practice phoresy (e.g. Uropodina, many Astigmata) which usually involves a specialised juvenile stage being carried by a larger host animal into an area with more favourable conditions. In some groups males use a penis-like adeagus for direct sperm transfer into the female reproductive system, while other practice indirect sperm transfer usually via spermatophores.