Identifying Parasite

[TortoiseshellJenny]

Not exactly sure if this belongs here, but after an 8 year break, due mainly to so many parasitic wasps, I am trying to raise caterpillars again. I had 47 caterpillars, and they are now all starting to turn into chrysalises. 17 so far have. I know they are Small Tortoiseshells, and from the fact that they shed their skin three times with me and it was consistently every three days, I think they must have been about 5 days old when I picked them up.

One of them seemed to have a black goop coming out its back end and I thought something had gone wrong with it turning into a chrysalis as it had not managed to anchor itself onto anything, but two dark reddish/black goops have just come out the back end of another caterpillar. I managed to get a photo but it's not very clear, and I did get some videos too but they aren't very clear either, plus I'm not entirely sure how to include them here. What also gives them away as parasites is the fact that the first caterpillar is almost certainly dead yet is still twitching every now and then. But with so many caterpillars in each container yet to turn into chrysalises, I am reluctant to open up the containers. I was really just wondering if anybody knew what type of parasite this was?

I did do a Google search, but the main parasitic wasp it kept coming up with was Sturmia bella and I know it's not that because they are white, are they not? Plus all of the chrysalises are so far okay.

[Vince Massimo]

Hi Jenny

The conditions you describe sound more like symptoms of a viral or bacterial infection rather than a parasitic attack. The affected larvae should be removed from the container to avoid others becoming infected. A general clean-up of the container may also be in order, like removing droppings and all old food plants. I'm not sure what sort of containers you are using, but improving ventilation should also help.

Vince

[Pete Eeles]

Hi Jenny - it sounds like your livestock is suffering from a pathogen (virus, fungus, bacterium, ...). Without knowing what type of container / cage you're using, it's difficult to provide any specific advice. In general terms, however, (and as Vince suggests) you need to sterilise whatever you're using since it sounds like the disease is being passed on from caterpillar to caterpillar. Any diseased larva should be removed immediately, the container sterilised, old food plant removed and clean conditions and new food plant provided.

Cheers,

- Pete

[TortoiseshellJenny]

Update:
So all but the two infected caterpillars, which are now dead, have turned into chrysalises. Also the two that this happened to were in different containers. I didn't keep 47 caterpillars in one container. They were split into 4 plastic lunch box type containers that I got from a supermarket, and I just punched holes in the top. Still a little nervous to disturb the chrysalises so soon after they have changed, as back in 2004 I had 4 Painted Lady Caterpillars, and when the fourth one turned into a chrysalis I turned the lid upside down exposing them to give them a bit of air almost immediately and the fourth one didn't harden in the correct shape so didn't hatch. Actually have some funny stories about those Painted Ladies.

I haven't done this for the last 8 years, and it was on a bit of a whim that I decided to try again this year, so the containers aren't perfect. I'll look back at all the problems I've had and see if I can come up with something better for the future.

[Pete Eeles]

... and I just punched holes in the top.

Actually, there's no need to do that; there's enough air inside most containers to last several days.

I turned the lid upside down exposing them to give them a bit of air almost immediately and the fourth one didn't harden in the correct shape so didn't hatch.

Newly-formed pupae should be left alone for at least 24 hours to allow them to harden.

You might find this article useful: http://www.dispar.org/reference.php?id=87

Cheers,

- Pete

[TortoiseshellJenny]

Newly-formed pupae should be left alone for at least 24 hours to allow them to harden.

Which is exactly why I wanted to leave them for a bit. Unfortunately I have already cleared out two of the containers, although not the ones with the dead caterpillars in them. I hate doing anything to chrysalises. I don't even handle the caterpillars. I discovered I've lost one chrysalis to this as well (in a different container to the other 2, but I did manage to very carefully remove it), and I think one of the chrysalises is a bit malformed, so so far I think I have 18 healthy looking (touch wood) chrysalises, and one that may not hatch, 8 in one container and 11 in another. The 8 of them in one container actually couldn't be better. They are all hanging upside down, nicely spaced apart, and all look healthy, so with any luck, as long as I just leave them alone, I'll have at least 8 hatch out.

Great article though. I skimmed through it but I think I'll print it out. I might be an amateur at this, but I've been raising butterflies since I was 3. I started with Large Whites and they would usually be just about to hatch as we went on holiday, so we would just take them with us, as we would usually just drive four or five hours away. In later years I moved onto Peacocks and Small Tortoiseshells, and also had 3 Painted Ladies and one Red Admiral (which turned into a chrysalis within 24 hours and hatched in 9 days!!) I don't really raise moths as they tend to hibernate as caterpillars over winter, although when I was younger we did hatch a female vapourer moth, and I used to see loads of Grey Dagger caterpillars around, but they now seem to have disappeared from the North of Glasgow. I did it right up until I was 20, 8 years ago and then stopped, but all the boxes I originally had got cracked as I used them for other things. Like I said, starting again this year was on a bit of a whim, so next year I'll make sure I'm a bit more prepared.

I'll give an update on chrysalis numbers when I've cleared out the other 2 containers, and then I'll update again on how many hatched.

[TortoiseshellJenny]

Okay, with the help of my Mum, I have very, very carefully cleared out the other two containers, and I have 14 chrysalises in one container and 9 in the other, so that means I hopefully have 41 chrysalises that could hatch. I'll let you know how I get on, but if all 41 hatch, I don't think 41 out of 47 is too bad for one year of rearing caterpillars - that's an 87.2% success rate.

Also, I read your article Pete, and I couldn't believe there are companies that sell butterflies for events! It was the first I'd ever heard of it and I was outraged. That is completely unethical.

[David M]

Also, I read your article Pete, and I couldn't believe there are companies that sell butterflies for events! It was the first I'd ever heard of it and I was outraged. That is completely unethical.

Hear, hear.

This kind of practice saddens me too.

[Jack Harrison]

TortoiseshellJenny wrote:
... and I just punched holes in the top.

Pete: Actually, there's no need to do that; there's enough air inside most containers to last several days.

As a youngster I always punched holes in lids. That is quite unnecessary. I keep the container with eg Orange-tip pupa (in the fridge) firmly closed throughout the winter and have a much higher survival rate than if left outside. But this clearly depends on may factors, eg the species.

Jack