Preparing Chrysididae

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Preparing Chrysididae

Postby Alex » 27 Jan 2016 19:36

Thought I'd write up a small example of a way to prepare Chrysididae onto clear plastic tabs, as some people have asked me about it. Might as well just make a post and link people to it.

Intro
Preparing chrysidids is not easy - I spend far too much time doing it, partly because I'm a bit of a perfectionist but also because I enjoy the results. However, the most important thing by far is not actually the preparing itself, but the way the specimens are killed and stored!

Collecting and Storage
If specimens are killed and/or stored in ethanol, the muscles and other soft tissues become permanently hard, almost impossible to re-soften to any adequate degree for nice mounting. Even after drying, or directly from the wet storage. Obviously it is good for preserving DNA, especially when specimens are stored at high (>96%) concentrations (water destroys DNA over time, so the less there is around the better) or taken out and allowed to dry quickly after pinning/gluing.

I use ethyl acetate or simply a freezer (if close to home) when collecting, which makes the specimens very soft as long as they do not dry, and even when kept dry for many years they are easily re-softened with water. Or even better by a mix of ca 10% acetic acid in water (I buy acetic acid that people use for pickling vegetables & baking). This mix also works better than pure water to soften ethanol stored specimens, but still not very well. Specimens can also be stored for a long time in a jar on top of tissue paper wet with the acetic acid, although I have not tried this myself -> link, also contains a lot of useful info about prepping, labeling etc.

Some coleopterists use hot water as a way to make stiff specimens soft, especially large beetles, but this technique should not be used with chrysidids! The reason is that the hot water permanently changes the colours of the specimen, as it changes the dimensions of the multilayer cuticular reflectors that produce the structural colours, and thus changes the wavelengths that are reflected back/absorbed.

Items


1) A pair of fine forceps 2) Clear acetate plastic tab 3) Specimen to be prepared (Trichrysis cyanea female in this case) 4) Some fine brushes 5) A thick, size 4-6, pin in a 0.5 mm mechanical pencil (nylon pinhead removed), I find this much more useful than just gripping a pin with my fingers 6) Pins of various sizes

Not pictured; Glue (I'm using animal based, water soluble entomological glue, but any water based glue will probably work), dilute acetic acid (10%), syringe (see below)

Re-moisturising specimens
My specimen was dry, so to quickly make it soft again I used the "syringe"-method. If the specimen is already soft just skip this step.

7) specimen added to a syringe together with the acetic acid solution 8) all the air is pushed out and a finger placed over the opening 9) the plunger (purple bit) is pulled back slowly (if done to quickly it can sometimes damage specimens, but its rare) creating a low pressure inside the syringe with draws air out of the specimen and replaces it with water 10) let the inside pressure equalise.
Do step 8-10 maybe 2-4 times depending on specimen size, how dry it is, if you can still see large amounts of air escaping from the specimen etc. Take out the specimen and remove excess water with a bit of tissue paper.

So now you hopefully have a soft specimen, its time to start the actual prep work.

Prepping

11) Put the specimen on its back on some moist paper or on foam, under the stereo microscope
12) Remove genitalia/ovipositor with a fine pin or very carefully with pair of forceps. Take care not to crush the genital capsule in males. Next open up the mandibles, extend wings (pin down if needed), antennae, then legs to make sure everything is soft and movable. It doesn't matter if the body parts spring back to a bunched up position after you let go of them, its mostly to make sure everything moves. It can take a while to get comfortable manipulating small things under the scope, its simply something that has to be learned by doing. Imbibing large amounts of caffeinated drinks beforehand is not advised ;) .
13) Turn the specimen around, readjust the legs if underneath the body. On large or especially uncooperative specimens I use pins to arrange the appendages in this step and let them dry an hour or so before continuing. If things does not move, or start drying, add some dilute acetic acid with a brush or a forceps to the stuck body part, and see if it helps. 14 Clean the plastic tab with water or better ethanol to get rid of dirt and fatty oils, pin it, and using a pin scratch the small area where the thorax will sit, to let the glue have something to adhere to. I went a bit over board this time, just a few scratches will be enough.



15) Put a small drop of glue on the plastic where the thorax will be positioned, the glue shouldn't be so thin that it gets drawn up all over the specimen by capillary action.
16) Lift the specimen into place, and push down on the thorax so it really sticks to the glue. Also glue the ovipositor package to the tab so its not lost 17) Use brushes, pins, forceps together with acetic acid mix to get the wings legs and antennae in position. To get the wings out of the way add a small drop of water to the edge of the plastic tab and they should stick to the surface tension. If certain appendages are very "uncooperative" you can add a small bit of glue underneath them. But usually the surface tension of the water is enough to hold things in place. 18) Place the pin with the tab end down against the foam so you get this view in the scope.

If you want you can stop after step 17, but as the wings are pointing straight out specimens will take up more space in a collection and will easily get damaged when handled. To some degree the wings also cover some parts of the mesopleuron in lateral view.


19) Another shot of the angled specimen, take care so that the end of the tab is firmly up against the foam to prevent any movement of the tab. 20) Set one pin underneath each wing pair, then add the pins above. The pins should press against each other just a tiny amount, or at least touch. If the wings are hard to put in place add some acetic acid mix to the tegula and wingbase, it usually helps. Sometimes its enough with just pins above or underneath to get the wings in position, but when the specimen dries they often start to move. 21) The completed prepared specimen, let it dry in this position over a couple of days before removing the pins.

It can take a long time per specimen, but with soft specimens it becomes quite easy and quick after a while. Its certainly not the only way of doing, or the best way, but its what I've come up with by experimenting over the years.

Hope this guide is of some use!
/Alex
Last edited by Alex on 27 Jan 2016 22:13, edited 5 times in total.
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Re: Preparing Chrysididae

Postby Alex » 27 Jan 2016 19:55

When the specimen is glued to the tab parts of it often dries before the prep is done, or the glue prevents a femora to move etc. It can then be hard to add small amounts of liquid to a specific area without covering the whole animal in a drop of water, or disturbing already correctly placed body parts. Using a single pin to add liquid is next to useless as the drop rises away from the pin apex only to "jump" over to the specimen as soon as it comes into contact with the drop. Brushes, even if small, are hard to control in my experience and often does not let go of enough liquid.

I find the forceps very useful when adding controlled amounts of liquid to specific areas. Simply dip the closed forceps tip in the water/mix to pick up a tiny amount of liquid. Then by adjusting the distance between the two forcep-prongs its possible to add small amounts of liquid to very specific points. For example a single antenna, or even just a part of if:


I even keep a large drop of water on back of the plastic tab to draw from, that way its possible to work under the scope the whole time.
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