Caddis Fly

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 I had a walk down to the bottom field today to have a look at the stream. In Cumbria the stream is called a "Syke" or "Sike" meaning that it is a stream that sometimes runs dry; these are especially common on a limestone bedrock where the stream percolates through the rock and often continues to run underground. I turned over a few stones and the most obvious things to see were the caddis cases. These images are of the underneath of stones that were submerged in the stream.



These stone structures are made by the larvae of the caddis fly (otherwise known as the  sedge fly). The larva use silk to bind together pieces of whatever substrate is lying about (some cases are made out of little twigs for example). The structures are hollow tubes and water (with oxygen and food) is sucked in at one end and blown out of the other. The larva moving about in the tube helps with  the water circulation.
Often the flies hatch out all at the same time (an emergence) and this is an important source of food for fish, bats, and birds. The flies look a bit like moths but with hairy rather than scaly wings and are mostly nocturnal. Caddis cases are a useful indicator of relatively unpolluted water as they don't tolerate pollution well and are big enough to be easily identified in the field. We do get fish and eels in our stream but it tends to get silty and water from the road drains into it as well as fertilisers washing off the fields.
Many years ago itinerant tinkers would go from village to village selling pans and kettles and so forth. For ease of carrying they often sewed the pans onto the outside of their coats. Little wonder then that they were often known as "caddis men" for their resemblance to the caddis larva cases.
Whilst I was at the stream I noticed this common blue damsel fly - it must be a male because the females aren't blue!

Our stream, a narrow trickle at this time of year but floods in the winter. This is a tributary of the River Eden.

Diary
Overcast this morning. Fox on the trail cam last night. Moth trap produced 23 moths and two cockchafer beetles and 4 burying beetles. A brimstone moth too - the first this year.




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