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Hooked pins

Making and mounting a hooked pin

There are two recipes here: one for a basic mounted hooked pin and one for the new improved Washington hooked pin.

The basic mounted hooked pin

You’ll need a headless entomological pin. If you don’t have any headless pins, snip the head off a headed pin with wire-cutters. Holding the pin firmly in pliers, press the point hard against a pane of glass and drag it to one side, keeping it at about 90º to the glass. Examine the tip under the microscope to see if you have rolled a satisfactory hook onto the end. You might need a few goes. Surprisingly, this causes no perceptible damage to your windows!

Larger pins can be mounted in the Watkins & Doncaster needle chuck (D431 Universal needle holder). But you might just as well mount the pin in the end of a matchstick, a piece of thin dowel, or an old pencil. Holding the pin with pliers again, push the non-hooked end into the wood. To make it easier, you could make the end of the pin sharper by snipping it diagonally with the wire-cutters. Once you’ve made a hole, take the pin out again, dip it in superglue or epoxy resin and then glue it back into place.

The Washington hooked pin

Clive Washington writes: “I have never been a fan of the plain ‘hooked pin’ for extracting genitalia. It is generally too springy and can easily catapult the specimen across the room [too true!]. It’s also easily damaged or bent, and when mounted in a pin chuck feels badly balanced and clumsy. I thought it would be a good idea to have a much thicker stiff pin with a very fine end. These are actually available from specialist microscopy suppliers for a frightening price.

My solution to this problem has been to use a syringe needle as a handle for a hooked micropin, with an appropriate length of the micropin protruding from the hollow end of the needle. In my case I use a B3 micropin which has been hooked by brushing it across a glass plate, then I put a bend of about 30 degrees in the centre of the pin. Using fine-nosed jeweller’s pliers I then push this kinked pin into the sharp end of a 27g 0.5 inch long syringe needle. When the bend on the pin enters the needle it will of course take quite a lot more force to push it into the needle (that’s what holds it in of course) so be careful not to slip and impale yourself. My preference is to leave about 2mm of the hooked micropin sticking out of the syringe needle end. You can make different sized versions but this small one suits me. I’m quite comfortable holding the syringe needle by its plastic hub but if you want a larger grip then the needle can be mounted on any sized plastic syringe barrel.

Since making this tool I have dissected several dozen Stenus, various Staphylinini and some flea-beetles and have not yet lost a specimen. The needle is much stiffer than the plain pin and handles sensitively. It’s still in good, unbent condition and when it does start looking tatty then it is the work of a few minutes to replace the whole thing afresh.”


2 Comments

  1. Don Stenhouse says:

    Quite ingenious Clive!
    I have used matchsticks and Lydie Rigout needle holders (which I stick with now) but find that it makes sense to make the pin as short as poss – I too have sent genitalia flying through the air! The pin holders tend to go rusty just where the chuck screws on. I have a few syringe needles knocking about so may try this.

  2. Clive Washington says:

    I’ve now further modified my technique, as I get older I find I like to have something more substantial to hold. I now use disposable wooden chpsticks as handles. Several billion people have been using these for thousands of years and they seem to quite like them. The end of the stick is finely tapered by sanding, then split or slit with a fine saw, and the micropin sealed in place with superglue. The whole thing is tidied up to the finest possible point by sanding when the glue has set. The critical thing is to have as little pin sticking out as possible, mine are about 2mm protruding. The wood stick is an excellent support, being rigid and damping any possible vibration and springiness.

    If you use good quality pins, then it will be hard to put a hook on the end by tapping it on glass, as the end will simply snap off. The solution is to let down the temper on the pin by passing it through a flame for a second. You can then craft an extremely fine hook on the end. However you won’t be able to re-harden it so it wil be more vulnerable than your straight pins. Mark this pin holder with a red ring so you can find it quickly.

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