Monday, February 15, 2010

Losses of hibernating larvae

Checked hibernating iris larvae in my Wiltshire wood yesterday. Although there was no St Valentine's Day massacre, I must report that two larvae were lost to apparent predation during the first half of February and another has shrivelled up and died. This is the second larva that has done that over the last month, and I anticipate more as some others are looking a bit small and shrunken. I should have measured them. Next time I will.
The problem of hibernating larvae shrivelling up and dying is familiar to those of us who breed iris. Does anyone have any idea what causes it? From my limited captive breeding experience the problem seems to be prevalent in some winters, perhaps wet winters; and it occurs mainly in late winter / early spring.
Possible explanations are:- 1) winter weather - is desiccation associated with particular types of winters? 2) Poor food plant quality during the autumn? 3) some form of virus, which may be weather triggered?
The two larvae that have succumbed were in very different positions; one was in a fork, the other on a bud.
So, at present I seem to be losing one a week to predation, and now have 29 left. Nearly all apparent predation has been in one area towards the northern end of the site, where flocks of tits are particularly active.
The things one stoops to in the interests of science! My natural inclination is to put little gauze cages round each larva to keep the predators off...

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