This behaviour may be interpreted as a consequence of competition between many males for few females. In other species the males guard their females at least for the time necessary for the spermatophore to discharge its contents into the female. Sometimes a complex mating behaviour precedes copulation. Females in such cases may be endowed with effective mechanisms to keep off males from copulatory attempts. A few hours or days after copulation eggsacks are formed by the female.
Most species produce paired eggsacks .
These sacks are carried outside the body under the abdomen and consist of eggs embedded into a mass of secretions. Depending on size and life style a few to several dozen eggs develop inside their protective cover. Some parasites produce several thousand eggs. The eggs are probably still nourished by the females. After a few days the larvae hatch and the eggsack is cast off.