Preserving large Lepidoptera pupae

[lamprima2]

I have a few large (50-60 mm) Sphingidae pupae that I like to preserve rather than wait for the hatching. I guess the most "scientific" way is to preserve them in alcohol or formaldehyde, however, I'd prefer keeping them pinned in the drawer. Should I immerse them first in alcohol or acetone and then let them dry? Alternatively, I could keep them for a while covered with silica gel granules. Or euthanize them by freezing, pin, and dry in the container in the presence of desiccant, such as CaCl2?
Please advise.

[Trehopr1]

I must admit that I have never tried preserving moth pupae however, I would be inclined to probably drop them in a bottle of 90% rubbing alcohol and leave them there for a couple of months and then pull them out and pin them.

90% rubbing alcohol really stiffens up anything you drop in it and by submerging it or them the alcohol will thoroughly saturate the pupae inside and out stiffening up everything quite nicely and you should have no ill effects afterwards.

As to some of your other suggestions I cannot comment but they all sound reasonable. Others can certainly chime in on any ideas regarding those other methods or chemicals.

I believe my suggestion also remains much safer than say acetone which is so much harsher a product and it might possibly discolor the natural coloration of the pupae --- in some cases.

[lamprima2]

Trehopr1,
Thank you for your reply.
Alcohol can certainly fix the proteins in the pupae, however, it
cannot dissolve the fat. That's why I thought about acetone which can replace both water and fat (the pupae are dark brown, almost black, there is no problem with discoloration). Perhaps, this is an overkill and I just need to pin the pupae and let them dry out. I was looking for a simple practical solution, based on someone's experience. I cannot believe that no one on this Forum has collected dried pupae.

[lamprima2]

Update on large pupae processing:
Manduca sexta pupae were euthanized by freezing,
and stored in 80% ethanol for two months. The result was disastrous: upon drying, the pupae became covered with whitish flakes. It looks like the outer layer of the pupa's cuticle (epicuticle?) is peeled off. Next time I will simply pin the pupa and let it dry in the presence of CaCl2 or bury it in silica-gel, rather than exposing it to organic solvents.

[Trehopr1]

Hello lamprima2,

Very sorry to hear that your experiment was disastrous. I was afraid that using any man-made solvents would severely dry out or damage the test subject.

This is why I suggested using 90% rubbing alcohol. At the museum where I worked for 8 years we stored many things in 70% alcohol but, we also stored other things in 90% to fix the tissues without necessarily drying them out.

I've never known 70% or 90% rubbing alcohol to damage anything. Yes, initially when you drop something in it there is an exchange of bodily fluids and rubbing alcohol and this is where you will see the rubbing alcohol change color. However, once you dump out the bad alcohol which has become discolored you refill it and check it again in a little while to see that it still remains clear.

Wishing you better luck next time if you have another test subject.

[jhyatt]

I would think that freeze-drying would be the best method to preserve large pupae, but of course you'd have to have the proper equipment to do it...
jh

[lamprima2]

Trehopr1 and jhyatt,
Thank you for your replies.
I did exchange the alcohol solution a few times until it became clear.
There is no problem storing any specimens in alcohol,
however, my goal was to preserve dried specimens.
I do not have freeze-drying equipment.

[Trehopr1]

Perhaps, lamprima2 just let it "fix" itself for a little while in the 90% alcohol and then put a pin in it and let it dry.

The older cuticle of the pupal case should be thick enough and strong enough to be just fine and in time the insides will dry out and harden.

Then you can have your pinned.specimen.

[lamprima2]

My backyard has no shortage of M.sexta, and our local Home Depot has
plenty of Jalapeno. I'll try again, and let you guys know.