Sunday, 3 December 2017

Starting to retain specimens - a simple guide

Some photographic recorders start to want to know what they are missing out on - there are frequently species that cannot be done from photographs and it is frustrating not to know what they are, especially if you are trying to generate a picture of what occurs in a garden or favoured wildlife site. What can be done?

The option several members of the UK Hoverflies Facebook group have adopted is to collect specimens and store them for the autumn when they send them to me for identification. I have written about this before, but it is always worth an update.

Killing specimens

There are several ways of doing this:

The simplest is to pop the container with your fly in it in the freezer for 24 hours - very few summer insects will survive such a time in the freezer.

An alternative is to use ethyl acetate or nail varnish remover - couple of drops on a piece of tissue popped into the container (beware that Ethyl Acetate is a solvent of some plastics, especially polystyrene which is often used. So, if in doubt use a small glass tube.

A further alternative is to take the fresh early growth from cherry laurel and crush it up into small fragments before putting as a deep layer in a tube or bottle and covering it with a wad of tissue paper - tightly pressed down. This is the traditional entomologists' 'killing bottle' and makes use of the cyanide released from these young leaves. I use this system for bigger flies, sawflies and other Hymenoptera (and any other big insects that are otherwise difficult to kill quickly).

Storing specimens

In an earlier post I showed how John Bridges does this using little plastic envelopes. It is a great system but he and I did hit a bit of a problem with mould, so I think that the alternative is to use a breathable envelope - I have previously shown how to make these too but here is the sequence again:

Stage 1. cut a piece of paper about 7cm square

Stage 2. Turn one side over to form a triangle

Stage 3. Turn over one side to seal the edge - it is often a good idea to stick this down with a slip of masking tape.

Stage 4. Put relevant details on one side that will not get torn when the package is opened. Key data = Date and Grid reference. My package is for specimens collected in the field and stored for several different schemes so I also put my initials and the group it contains.

Stage 5. Place your specimens inside to envelope - in this case fungus gnats from one site visit. In the case of hoverflies it is not a good idea to put more than one per package as they are bulky and if they lie next to one another they may form a damp area that attracts mould.

Stage 6. turn over the open end and again seal with masking tape.
These envelopes should be left in an open ventillated place for perhaps 24 hours so as to aid drying. After that I would store in a box - probably best to be breathable rather than a sealed plastic box that can build up condensation and mould - I have had problems in the past with mould and now leave my specimens in a more open situation for several days before using a cardboard box to store them.


I once sent an envelope of fungus gnats to Peter Chandler in a poorly protected package - he later wrote to say that they had arrived  in many tiny pieces but he had managed to construct a list from the genital capsules of some of them! That was an object lesson for me, so I now send my samples in plastic boxes - the sort you get from a takeaway Chinese meal.

What happens next?

When specimens reach me they go into a box of samples awaiting identification - which I do intermittently; which reminds me .......! I have several to do and had better get on with them today!

And the benefits?

Eventually, you will get a spreadsheet back from me detailing what you have caught. This spreadsheet will also go on the HRS database so there is a more detailed account of species in your area. This in turn helps both distribution mapping and our knowledge of species' abundance and phenology. It also helps to improve the interpretations of distribution using predictive models that use occurrence data to predict distribution and to assess trends (e.g. Frescalo or Maxent).

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