Things to think about

When collecting for science (as opposed to 'pretty displays') there are only usually 2 things to think about:

1. How best to protect the specimen in the short & long term?
2. How best to present the specimen so that it can be identified as easily as possible?

With each group of insects you may find different answers to these questions, depending on how hard/soft the specimen is and which features are used in the identification keys. Some keys assume that specimens are preserved in alcohol (eg. spiders / molluscs) and others assume they will be dry (eg. most insects).

In the following article I will assume that we are talking about Diptera & Hymenoptera (my specialities). Also, please remember that a lot of this is my personal preference - other people might/will disagree!!

Mounting specimens

I pin most specimens on their sides (lateral pinning) with very fine micro pins; slightly diagonally so that I don't destroy the same feature on both sides.

I then make a 'stage' using a thin strip of plastazote (high density foam) and push a thick (size 3 or above) 'continental-sized' entomological pin (the 'stage-pin') through one end so the stage sticks out perpendicularly. The micro pin is then pushed firmly into the foam stage.

The stage is positioned half way up the stage-pin, to allow room underneath for labels, but not too close to the top of the pin where fingers are likely to interfere with it. (see right).

Staging combined with side-pinning protects small/medium specimens very well while displaying as many features as possible. The stage-pin is strong and easy to hold/manipulate when moving the specimen and the stage absorbs most vibrations.

This method lends itself very well to bulk-collecting of groups that take a while to identify.

I will go out for a day in the field and catch maybe 50 insects of various orders and families. I pin them with micro pins and immediately put them in a flat, clear, plastic box with a sheet of foam at the bottom (see right) and 1 label containing all the data for that group of insects. At this stage they have not been identified so all we know about them is the collection data.

When I have time to identify them I put a specimen on a stage; identify it; and put the specimen's labels (copy of the data & a seperate label for the name) on the big stage-pin, under the stage.

Alternatively you can direct-pin (see right), 'top-down' (dorsally) but I only do this with very large specimens (eg. Tachina spp. or bigger).

Also, with Hymenoptera many people prefer gluing the insect to strong card but I feel that very fine micro pins are

• much easier to use (glue is very messy)
• allow for moving later (glue can be dissolved but it isn't easy)
• need not destroy much/any surface features

But in general I like to have 1 mounting method for most of my specimens and glue doesn't work well for groups like Diptera, which have fragile bristles.

Equipment

My standard kit (see right):

1. L-shaped foam block for holding pinned specimens under the microscope
2. drilled aluminium pinning block for positioning stages & labels at uniform heights on the stage pin
3. very fine waterproof ink pen for writing labels (0.1 thickness)
4. box of continental-length pins & pre-made stages
5. box of spare foam strips for stages and some glass tubes containing micro pins and more continental pins
6. small pair of scissors (for cutting up labels)
7. curved and straight pointed forceps (I don't like the grooved 'entomological' forceps because they 'twang' pins too often)

This all fits neatly into a plastic 'tupperware' box for storage and transportation.

Pins

I use a variety of different pins for different jobs:

• "Continental" length (38mm, size 3 or 4 - approximately .55mm diameter) pins for use as stage-pins or sometimes for direct-pinning very large specimens. I would never use a thinner pin because thin pins flex too much and, although they push into foam relatively easily, you will have to push them into cork at some time and this is much harder! If the specimen is small enough to need a thinner pin then you should be staging it.
• Micro pins for direct-pinning most of my specimens:
  • D3 size (0.01" x 10mm) for larger specimens
  • A1 size (0.0056" x 10mm) for anything small

Microscope

A good binocular microscope with lighting system is an essential part of any entomologist's equipment and is probably the most expensive thing you will buy. Ideally you want to invest in something that has very good optics and a good, bright white light. You don't need to have very strong magnification - about 5x-40x is perfectly adequate for most flies & wasps. When you are ready to buy a microscope the main thing is to try out plenty of different models and test them with a few of your own specimens.

Mine is a MEIJI zoom binocular microscope with a zoom range of 0.7x - 4.5x and 10x eyepieces giving me 7x - 45x total magnification. The light is a small Mini-Fluor fluorescent light attached to the microscope itself.

I do occasionally struggle at the top end when trying to identify something really tiny like a pteromalid wasp, collebollan or see the detail on a Siphona epandrium. But I just know my limitations and avoid these as much as I can. In most of these cases (when you get to magnifications over 50x) it would probably be advisable to prepare slide mounts and use a stage microscope instead.

You might also like to think about buying a spare 10x eyepiece fitted with a graticule. A graticule projects a grid or measuring line onto the image and allows you to measure distances and ratios accurately. This is very important when trying to work out the relative width of the frons in tachinids or the ovipositor/tibia ratio in ichneumonid wasps.

Working with genitalia

Some identifications either rely on being able to examine the male genitalia or you can use the genitalia as a good confirmatory character. For this reason I always recommend that if you have a male dipteran you should always try to hook out the genital capsule when you first pin the specimen. You might not need to do it but it's much easier to do while they are soft and pliant, than try to relax an old specimen later.

All you need to do is to use a fine micro-pin and gently tease open the genital capsule. You should find that it hinges on its dorsum and you can hold it open with a few crossed micro-pins until the specimen has dried and is set (see right).

Sometimes you will have to remove the genitalia completely and in these cases they can be clarified in a weak solution of potasium hydroxide (KOH) but it isn't usually necessary. Be very careful with this chemical - it is strongly caustic and care should be taken to keep it away from the skin and eyes! In either case I normally store separated genitalia in little plastic capsules that can be pinned beneath the specimen, just above the data label (see right). The genitalia are suspended in a solution of glycerine.

Alternatively, some people choose to store the genitalia in a chemical called DMFH. When dry DMFH becomes a hard, long-lasting and transparent droplet that both protects and holds the genitalia, yet allows it to be examined and can be dissolved later if necessary.

Labels

All specimens should have at least 2 labels:

• the data label (under the stage) containing:
  • Place of capture (region, place name & map reference)
  • Date of capture (often with the month in roman numerals)
  • Name of collector
  • (optional) method of collection
• the determination (or 'det') label (usually the lowest label) containing:
  • Species name
  • Sex
  • Name of determiner
  • Year of determination

If the specimen was reared from a host or collected as a larvae you might also want to give it a rearing label (under the data label) containing:

• host name
• date of capture
• any other notes relating to the rearing

These labels are made from card or thick 160gsm paper so that they don't drop or rotate on the pin. Never use thinner paper - it won't grip the pin properly and it will start to spin round and need replacing very quickly.

I normally print as much of the static information as I can, using laser or inkjet printers fitted with indellible inks. At the begining of each year I print:

• A sheet of part-completed data labels for each of my favourite collecting sites containing all the information except the day & month of collection.
• Sheets of completed det labels for the groups I study most frequently. I collect a lot of tachinids and I am also asked to det tachinids all throughout the year so it makes sense for me to carry around sheets of pre-printed det labels to save me having it write them each time. Obviously, I print more labels for the common species and less of the rarities.
• A sheet of 'blank' det labels (with just my name and the current year) which I will use for all non-tachinids.

Storage

As I mentioned earlier, I use the flat, clear, plastic boxes for unidentified specimens and they keep everything clean and dry and take up very little space.

When the specimens have been identified they go into long-term storage - a larger, wooden store box (see right). Second-hand boxes can be bought from most natural history museums and you can just line the bottom with a 5mm or 9mm sheet of Alveolit foam. Alternatively you can buy new boxes from entomological dealers.

As long as these store-boxes are kept dry, indoors the specimens inside should be safe for decades. If you are worried about pests (eg. Anthrinus beetle larvae) getting in and eating the specimens you can always freeze them for a week or more in a domestic freezer. Museums do this as a matter of course because many insecticide chemicals (naphthalene etc) are now banned.

I arrange identified specimens in 4 vertical rows, using the longer axis of the box. They are grouped taxonomically down to sub-family and then by genus/species alphabetically there after. But with larger collections you might want to group by tribe too.

Posting specimens

Sometimes it might be necessary to send pinned specimens to another expert for identification. This need not be a problem as long as you have good, sturdy boxes with a deep (9mm) later of dense foam attached firmly to the bottom. Into this pin your specimens and if you think the stages might spin you can hold them in place with more 38mm stage-pins.

It is also possible to send specimens from Malaise trapping in glass tubes of alcohol protected by plenty of cotton wool and a sturdy cardboard box. But this might cause some raised eyebrows if you send them internationally because customs never like to see alcohol being brought into the country, whether it has flies in or not!