Posted by Andre on 08-01-2008 13:32
#9
Tony Irwin wrote:
Can you tell me what evidence there is that this species hibernates as adults? I have seen Eristalis tenax and Eristalinus aeneus hibernating in buildings and caves, but I have never seen an Episyrphus hibernating - only flying aound or sitting on vegetation. I had always assumed that November and December individuals were active (often on Hedera blossom) through the autumn, and that individuals in March had emerged from overwintering pupae. Has anyone seen individuals or aggregations of Episyrphus actually hibernating in sheltered situations like Eristalis does?
From "Syrph the Net Species account":
" Flight period: February/ November, with a number of overlapping generations; overwinters as an adult and may be found hibernating among ivy, or in caves etc. On exceptionally mild, sunny days in mid-winter this species can sometimes be found in flight - presumably specimens that have been hibernating. Sarthou et al (2006) show that the occurrence of E.balteatus adults under these conditions is linked to availability of shelter and potential resting/hibernation sites (in forest), in an agricultural landscape. This species is a pronounced migrant."
So there's enough reason for discussion on this matter! Fact is that mainly female individuals are found flying in wintermonths...
Edited by Andre on 08-01-2008 13:35