Overwintering third instar larvae. From the left: stag beetle, lesser stag beetle and rose chafer.
Photo by Maria Fremlin. Colchester, Essex, UK. 5 February 2014.
Even though these three detritivore/saproxylic species live close together, a close examination of their gut revealed three different overwintering strategies.
1 - Stag beetle Lucanus cervus larva. Note how dark the body of this larva is body; its gut is full of food.
It seems that in a region with relatively mild winters, like Colchester where I live, stag beetle Lucanus cervus larvae carry on feeding at this temperature. And perhaps at even lower temperatures. I have observed an active larva in captivity feeding at 4 °C. These larvae are quite mobile and if the weather cooled down for a very long period they could always move down away from the frost line. There are stag beetles Lucanus cervus as far north as Southern Sweden, not to mention Central Europe - all regions with very cold winters. However, in those regions I do not know what their overwintering strategy would be.
2 - Lesser stag beetle Dorcus parallelipipedus larva. By contrast with the larva on the left, the body of this one is almost translucent. This larva has stopped eating. And it has prepared itself for the winter by emptying its whole gut and filling it with a special winter anti-freeze fluid. See below.
Dissected overwintering lesser stag beetle larva. Photo Maria Fremlin.
3 - Rose chafer Cetonia aurata larva. This larva has quite a different shape; note that its lower abdomen is rather dark. It has also stopped eating, but only its midgut is full of anti-freeze fluid; remarkably, the hindgut remains full; the hindgut is underneath the distended darkened area. See below.
Dissected overwintering rose chafer larva. Photo Maria Fremlin.
Further reading about overwintering strategies:
Insect winter ecology - in Wikipedia.
Neven LG, Duman JG, Beals JM, Castellino FJ (1986) Overwintering adaptations of the stag beetle, Ceruchus piceus: removal of ice nucleators in the winter to promote supercooling. Journal of Comparative Physiology 156:707-716.
Xu, L, Neven, LG and Duman, JG (1990) Hormonal control of hemolymph lipoprotein ice nucleators in overwintering freeze susceptible larvae of the stag beetle Ceruchus piceus: Adipokinetic hormone and juvenile hormone. Journal of Comparative Physiology B, 160, 51-59.
Walters KR Jr1, Serianni AS, Voituron Y, Sformo T, Barnes BM, Duman JG. (2011) A thermal hysteresis-producing xylomannan glycolipid antifreeze associated with cold tolerance is found in diverse taxa. Journal of Comparative Physiology B, 181(5):631-40.
Last modified: Mon Feb 22 2016
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