How I Pin Small Flies

This post is in response to a couple of questions received from Martin. Hopefully it will prove useful to anybody else reading this too, just to show that using micropins on tiny flies isn't necessarily a Dark Art best left to the professionals. Without doubt, I'm one of the clumsiest, butter-fingered, accident prone people out there, if I can do this then so can anybody. All you need are the right bits of kit.

I almost entitled this post "How To Pin Small Flies" but that would infer that I knew what I was doing and was following official guidelines, whereas in fact I just do it my own way which may be right or may be wrong. So here goes an account of this morning's exploits with a fungus gnat.

Sorry for the date stamp, I was playing with my new camera!

This is inside of the laundry shed I keep waffling on about. Usually there are laundry bags piled up everywhere, but it's empty at this time of year whist the hotel is closed for refurb. I painted the walls and ceiling last year to enable me to spot small insects more easily. Naturally, that's not quite how I put it to the bosses at the time...

A particularly well fed spider lives behind the edge of the bulkhead light!

Anyway, I grabbed a fungus gnat, plus two others, and brought it back where it was duly dispatched with a small dose of ethyl acetate. Here's a pic of the kit I use when pinning flies

Plus my microscope and a desk lamp!

If I was carding beetles I would dispense with the box of micropins and the strips of  Nu-poly and instead have my sheets of card, some glue and water, a small plastic lid that I use to mix them and a hooked micropin embedded into a match stick which I use to pull out legs and antennae etc. Most folks use a tiny brush for this but I prefer a hooked pin, presumably harking back to my days of microlep setting.

My micropin storage box

I used to keep my tubes of micropins loose in amongst various other bits and pieces of entomological paraphernalia, but occasionally the lid of a tube would work loose and I'd find hundreds of tiny pins strewn everywhere in the bottom of the Tupperware tub I kept everything in. So now I keep them all together in a plastic box which has a snap top lid. It just keeps them a lot safer and tidier and reduces the chances of spillage by about a hundredfold. As you can see, I labelled each tube with the different sizes of pin. I get mine from Watkins and Doncaster, so use their codes on my tubes which makes it a lot simpler whenever I need to order more. I use stainless steel headless pins which can be found by scrolling down here.

I have pre-printed labels that I use, all I need to do is fill in the date and add my name to the top label. The bottom label I fill out as and when I identify the beast in question to genus or species. If I can only identify it to family, I add a temporary label which could read, for example, "Chironomidae (625spp)". My hope is to replace these temporary labels with proper bottom labels, but some are unlikely to be progressed beyond family - or even superfamily - level anytime soon.

Right, so that's the kit. Now for the pinning technique itself. 

I lay the dead fly on a small piece of plastazote in the position I want it to sit on the pin. I decide which micropin size to use, this being entirely determined by the size of the fly and whether I intend to side pin or direct pin through the top. In reality, I almost always side pin small flies and almost always direct pin hoverflies but I tend not to follow hard and fast rules. It's a good idea to pin all flies that have been side pinned facing the same direction (ie left to right or vice versa) which not only looks neat and orderly in a storebox, but helps with direct comparisons with similar looking species. Sadly my flies are pinned facing every direction imaginable, something I need to work on improving.

All in readiness for side pinning. These happen to be A2 pins

There are a couple of tricks to pinning small, fiddly stuff like these. Without a doubt the most important being what you use to pick the pin up, followed by where to hold the pin as you move it. If you get those two things wrong you'll either end up pinging pins across the room, never to be found again until the day you step on it (lost micropins terrify me, I'm almost always walking around my room barefoot), or you'll find yourself unable to grip the pin securely enough to manoeuvre it around properly. This is my current weapon of choice 

The No.4 Superfine Stainless Steel Forceps

These forceps are not cheap (over twenty quid) but have been worth every penny. I've previously used blunt-ended or round-ended forceps with grooved tips to grip the pin more securely. And I used to drop lots of pins or send them twanging into oblivion, never to be seen again. But these fine-tipped bad boys are amazing, I hardly ever twang a pin nowadays. And it definitely helps to hold your forceps as close to perpendicular to the pin as possible; holding a pin with the forceps angled obliquely lengthwise along the shaft is far more likely to cause it to slip and ping away than if you hold it square across the shaft. One final word of caution; it is very easy to damage the tips of these forceps. I dropped mine onto the floor and bent a tip, resulting in my ordering a replacement pair since the dropped one could no longer grip pins properly. They come with a plastic sheath that sits over the tips when not in use which helps to protect the tips themselves and, as an added bonus, it stops me accidentally stabbing myself with them! Mine are always covered unless being used.

Back to pinning the fly

So here is my fungus gnat laying in the position I wish it to sit on the pin. I insert a pin into the plastazote next to each fly I am pinning (see previous pic above this one) making sure I have the sharpened tip at the bottom. That sounds pretty bloody obvious, but these pins are so very small and fine it's often difficult to see which end is which! I use my microscope to double-check if I'm not entirely sure. With the very smallest flies, a pin inserted upside down may badly dent the insertion point and will provide resistance when later mounting into a nu-poly strip, potentially enough resistance to bend the pin and send it twanging across the room never to be seen again. And taking your fly with it! So yeah, check the pin is the right way up, obvious as that sounds.

Note that I'm holding the micropin low down, almost where it is jabbed into the plastazote. I've discovered that this is a good, stable way of holding the pin and it reduces the effect of hand shake. Pins held right at the very tip nearest you will inevitably ping, so I hold them low down. You need enough pin exposed beneath the forceps to drive through the fly's body and into the plastazote beneath in one smooth action. Then, when it's securely held in the plastazote, slowly release the pin, raise the forceps further up the shank and push down some more until a good part of the pin has been exposed below the fly. Obviously there needs to be enough pin showing above the fly for you to be able to grasp it in your forceps and move it to the nu-poly strip.

Fly is now sitting roughly midway up the micropin

  

After that, it's just a case of inserting the pin into the nu-poly strip and using a mounting block to get the correct height for the strip and accompanying data label(s). Always make sure the nu-poly strip is firmly supported by a layer of plastazote when you insert the pinned fly (see pic further up the page) otherwise it will bend and the pin will go in at a funny angle. 

That's about it, really. I use a pinning stage to set everything at uniform heights but it's not completely necessary. I use a Pigma Micron 005 pen to write the data labels, which I've just found online here. These use a 0.2mm wide line of ink allowing me to write in clear but tiny lettering without any blurring or smudging.

Martin's second question related to the literature I use to get a fly to family. 

The Key to the Families of British Diptera by Unwin (1981) is available as a downloadable pdf or from various bookstores. I have the 1991 edition, which you can see in the image above. I'm not sure whether it's a reprint or has been updated from the 1981 edition. This is a good, easy to use key but should not be used for European flies as it is purely British orientated. I was warned that it doesn't always work out properly, and that proper grown up dipterists use the other book in the image above. So I went and bought that too. The European Families of the Diptera by Oosterbroek (2006) costs a whacking sixty quid, but it is just brilliant and if you really want to get into flies then you need to have this book, it's just that simple.