In addition to the ethanol tolerance mentioned by the other people who have responded to your question, some fly larvae are able to close off their spiracles. It is likely, given the low metabolic needs for oxygen in many insects, that they could "survive" for some time without breathing. Furthermore, the wax layer of the cuticle is often functions to prevent desiccation, but that means that it is unlikely to be very permeable. I too would be happy to try to help you with identification if you would like to share images with me

The adaptation Joachim refers to permits fly larvae from many families to develop in decaying substrates. Unless you intend DNA analysis, you'd be better dropping the maggots into near boiling water before moving them to ethanol for long term preservation. The reason is two fold: first it readily kills them; second dimensions of the larvae are preserved as the proteins denature quickly. In Ethanol, inter-segmental membranes become flaccid and the length (particularly) becomes unreliable.

PS: post me some images and I'll see what I can come up with regarding identification (or at least who best to ask).

What do you mean by survive ?

In addition to the ethanol tolerance mentioned by the other people who have responded to your question, some fly larvae are able to close off their spiracles. It is likely, given the low metabolic needs for oxygen in many insects, that they could "survive" for some time without breathing. Furthermore, the wax layer of the cuticle is often functions to prevent desiccation, but that means that it is unlikely to be very permeable. I too would be happy to try to help you with identification if you would like to share images with me

Thanks so much to all who've responded so far, great info and makes sense. I like the ethanol tolerance theory for lineages that live in decaying fruit where yeast is converting fructose to CO2 and EtOH, but it's a little puzzling that this species by all appearances is NOT frugivore, yet has kept that trait! Seems there is a potential paper in here somewhere. These larvae seem to be doing pretty well, likely adapted to consuming gastropod tissue. Next question we have is of the CSI variety: is this maggot potentially a cause of death of the snail, or arriving via egg deposition after the fact, i.e. mortality. Perhaps some good pics will help put an ID on it and get us closer to this issue. @ RG by "survive" what I intended to say was we observed them under dissecting scope and they continued to "wriggle" while submerged in the 80% ethanol for about 23-25 mins, at which point they ceased all movement.

We will get some images and post them. Thanks again.

Ah a snail parasite. Possibly Family Calliphoridae, subfamily Ameniinae, Amenia sp. Then again it could be Sciomyzidae or Sarcophagidae.

As to ability to survive in ethanol, I had a 500 ml jar full of American Soldier Fly (Hermetia illucens, Stratiomyidae) larvae from my overwet compost heap that survived (were still active) more than a week in 80% ethanol despite changes of the ethanol every 2 days.

Agreed with Christine above - there are calliphorids that are snail parasites. Likewise, could be another dipteran simply taking advantage of suitable food source.

Serves me right for not reading the description of the larvae. None of the aforementioned families (Tephritidae, Calliphoridae, Sciomyzidae or Sarcophagidae) have larvae with a dark sclerotised head. That character belongs to the Lower Diptera(previously included in Nematocera) and some Lower Brachycera. Images definitely needed.

Larvae of flies, when placed in any type of liquid substance capable of respiratory valve to close and stay alive for 20 minutes.

The cuticula of many dipteran larvae is very tough because they live in decaying or rotting substrates where they are subject to a plethora of substances that could potentially harm them. If you for example collect maggots from a cadaver the larvae will die from asphyxiation after some time. But if you don't heat the larvae up to at least ca +80*C anaerobic bacteria will continue to grow inside the maggot potentially ruining the sample. This shows that the cuticula can withstand alcohol for several years.

I think they are just not soluble in alcohol...^^

Like other animals with cuticle or with a thick enough skin. And as it has been told they can survive for a while under anaerobic condition after having closed their spiracles. Add some detergent in your 80% ethanol and their survival time rate will drastically reduce.

As pointed out above, the wax layer of the cuticle will keep the ETOH from entering the body of the maggot and the spiracular openings are often designed to keep the fluids external. In some cases, the spiracular openings may facilitate a plastron respiration, allowing for prolonged survival. When collecting it is essential to fix the maggots by placing them into a fixative, such as KAA, or into sub-boiling water to break down this layer and allow the ETOH to permeate the maggot. If this is not done, the maggot will decompose internally, leaving the cuticle relatively intact but useless for identification purposes. Proper fixation will also fully extend the maggot, allowing for the actual length to be determined and external structures observed. Typically I use the hot water method as it is easier and works as well as the KAA, KAAD, etc.

Dear colleagues, I personally am doing several studies on the establishment of fly larvae.

The death of the larvae in ETOH generally occurs within a few minutes (Blow-fly) by asphyxiation.

The problem dell'annerimento is given by putrefactive processes due to poor indoor penetration of ethanol in the tissues as a result of the processes of protein cogulazione. The ethanol should be used only on samples with dimensions of 3-5 mm.

I think Meaghan Pimsler suggestion that the larvae are able to close off their spiracles probably is the main reason they survive. This is the well documented method cockroaches use to resist drowning. Adding a little detergent to the liquid usually can circumvent this defense.

On a lighter note even houseflies, after such alcohol exposure in their juvenile state yield bad parents :-).

Hi Brendan. There are not many families of Nematocera or Brachycera that have larvae with banded cuticles, "spiny" segmentation, an anal extension/clasper, and are carnivorous/saprophagous on on dead animal matter. The size doesn't help either in terms of identification. To be honest I cannot find anything that fits the description at this stage so other colleagues requests for an image look like the best way forward. Of course we may be dealing with a Hawaiian indigenous species, which would make identification difficult for all us "outsiders".

The interesting thing about these beasties is that if they are nematocerans they would have spiracles on most segments (holopneustic, peripneustic or hemipneustic forms) or if brachycerans they are more likely to have only prothoracic and/or anal A8 (terminal) spiracles. There is likely to be a big difference in sensitivity to alcohol. Generally Nematocera are pretty sensitive to alcohol being mainly aquatic or semi-aquatic, so for my money the likelihood is that these are Brachycera of some sort.

In relation to the spiracle question. If these larvae were more or less full grown when you found them they may have been apneustic larvae, i.e. have no spiracles so they would "drown" and alcohol could only enter across the cuticle. As others have pointed out dipteran larvae generally have adaptations to limit a) water loss and b) chemical ingress so alcohol is slow to penetrate, which is why we need to kill in hot water to prevent internal maceration and discolouration, and allow the fixative to penetrate.

So with this little mystery I would be most interested to see what they are.

I used to keep at -70 degree Celsius, Anopheles gambiae mosquito larvae’s in ethanol 70 percent. After several months, for processing purpose, I opened eppendorf tubes 1.5ml containing larvae’s, I was surprised to observe that some of them are moving in a petri dish. I asked a colleague to be eyewitness.

Here's a pic of the beast in question. Not great quality but best we could get right now, length is ~1mm.

Dear Colleague,

I tried to make a immersion larvae of Calliphora in ethanol 70% v / v. The death came in 2-3 minutes.

Hi Brenden

Now we have an image it becomes easier. These are almost certainly moth fly larvae of the genus Psychoda (family Psychodidae). As they normally live in foul waters with high organic content, often with other unpleasant materials present, they would have a high tolerance for many materials, almost certainly including alcohol.

To add to the comments about fly larva survivability in harsh environments, I was involved in pest management in a vinegary... Fruit flies (vinegar flies) were of course abundant by the pound (from fly traps), but the amazing thing is that fly larvae were living quite happily in highly concentrated vinegar ... Vinegar is a weak acid of course, but I doubt most other larvae could survive this environment. The physiology of this adaptation must be fascinating.. Moth flies as described are also known as "filter" flies from sewage treatment facilities, and as noted, they can survive in very harsh conditions. Moth flies are an indicator organism in commercial kitchens and food processing facilities - showing deficiency in proper sanitation. I once saw them in an hospital day surgery due to organic accumulations at the base of an operating table. A bit of a shocker in that environment. The cleaning procedures which included crude mopping had resulted in this accumulation over an extended time. It signalled a total review of their procedures as well as upgrading of the maintenance at the base of the operating table by a meticulous sealing.

Hi,

Pleas check the level and activity of P-glycoprotein. I recomend http://www.ncbi.nlm.nih.gov/pubmed/13678840. However it is not about insects but may help to explain the case.

Maria

If you want to be sure and kill your maggots, you might want to heat the alcohol to boiling using a lighter.  Don't be too enthusiastic, or it'll boil over and there's always the chance of catching fire. The heat should cause them to open their spiracles and also help to "fix" the specimens so they don't turn black.  And, speaking from experience, brachycerans can live a looooonnnngggg time in 80% ETOH.  Then, again, these were stratiomyiids from Bad Water in Death Valley so they were probably a little more likely to be resistant to all sorts of things.

Genus Philosepedon (Psychodidae) is known to breed in dead snails. Larvae of this groups are very unknown. If you ever find them again, It would be great! I am currently working on Psychodidae larvae as well as adults. Tell me if you need any help with them.

Hi Danilo, thanks for your answer, so are you working with this group?  We breed endangered tree snails in captivity and simply found these larvae in a dead snail, and I think we wondered whether they might have contributed to the cause of mortality or were merely feeding on decaying tissue.