Just found this(knew I had it somewhere) from Stuart. It's a 50/50 mix not 70/30 as I said before...
Adult Caddisfly Collecting Notes 2010
If you get any adult caddisflies (but not the larvae) just put them into a tube. As soon as
possible put this into a domestic deep freeze for about 2 or 3 minutes. This is considered a
humane way to immobilise/kill an adult caddisfly, but please don’t leave them in too long as
they will drop to bits! Next, fill the tube with either neat vodka (or similar clear spirit such as
gin), or a 50/50 mix of isopropyl alcohol and water, any of these will preserve the caddisflies
until they can be identified. Please do not use neat isopropyl alcohol or surgical spirit as this
desiccates the caddisfly making it very difficult to work with while trying to confirm its
identity.
Write on a small slip of paper (see “Helpful Tips” below) in pencil, where (the approximate
location) and when (the time & date) you caught the sample along with your name. Put this in
the tube with the caddisfly samples (alcohol will have no effect on either the paper or writing
in pencil). Please do not stick a label on the tube as these, often, just fall off.
Drop the tube back in the post to me with your name and address along with any other notes
of interest on the capture. I can then post back another empty tube in return. You can put the
tube in any type of envelope, they do not need to be padded, these tubes are very strong and
will not leak. However, you will need to put a “large letter” stamp on the envelope due to its
thickness with a tube enclosed.
I do not get much chance to analyse samples until the long winter evenings, hence the reason
to preserve them in alcohol.
You can expect many different types of adult caddisfly to be on the wing from mid March to
the end of November. They range in size from 3mm to nearly 30mm and we have almost 200
very varied species, most are found near water but they can turn up anywhere, some are very
common and others incredibly rare. So, even if you only think you have one please send it
along for me to check. Plus, don’t worry if you think you have caught the same type twice,
again please send it along as this information is useful for the "flight period data".
At the year-end and after all the samples have been identified I will put together an annual
review. A copy of the review and data will then be sent to you, from this you will be able to
see the species you caught and sent in.