Invloed van voedselaanbod en stroomsnelheid op de microhabitatselectie door larven van de Bosbeekjuffer (Calopteryx virgo)

In The Netherlands Calopteryx virgo only occurs in unpolluted first to second order lowland streams in the east and south of the country. The distribution is strongly related to the high demands of this species to its habitat. However, little is known about the major factors driving its habitat selection, namely larval food choice and fouraging behaviour. Therefore, an analysis was made of the behavioural patterns of this species. In an experimental study, twenty larvae of C. virgo were observed in an aquarium and fed with waterfleas (Daphnia spec.). The prey was only caught when positioned in front of the head of the larvae for a few seconds. Literature suggests that C. virgo might catch its prey by using mechanoreceptors, which observe vibrations in the water caused by prey movement. However, vibrations of the water are difficult to distinguish from vibrations caused by prey. Therefore, C. virgo larvae probably occupy a microhabitat that protects them from turbulence, at least during predation activity.