Spontaneous generation?

[dbur]

They told me in grade school it didn't happen.

I found this tomato worm in the driveway. I dumped him in a bucket and a few days later he had turned into a cocoon. I put him in a cup with a lid. Over the space of one night these little maggot worms appeared in there with it.

I tried to stack some but the little worms kept moving, in slow motion, but enough to make the stacks difficult.

1x no stack:


~1x, 7 image stack PM with lots of wide area retouching:


~3x, 9 image stack. One of the cute little maggot faces smiling for the camera (or maybe it's the other end):

Isn't he sweet?

[Pau]

Your teacher was right . You can find a better explanation.

May be parasitoids emerging of the big coocon?
or perhaps someone wanted to complete your collection...

[Harold Gough]

The pupa is a typical Hornworm (aka Hawkmoth) type.

The larvae are of those of parasites. I would normally expect to see cocoons containing braconid wasp parasites:

http://www.cals.ncsu.edu/course/ent525/ ... sites.html

The larvae in your images look more like Diptera, the two dark structures being posterior spiracles.

I believe it is this Tachinid Winthemia manducae:

http://colinlmiller.com/wildlife/dipter ... themia.htm

Harold

[ChrisRaper]

Looks superb - definitely tachinid larvae - just let them pupate and emerge and let's see what they turn into Tachinids are much more interesting than moths anyway! If you get flies and would like them identified I would be happy to take them and key them through.

[Harold Gough]

Tachinids are much more interesting than moths anyway!

Bravely spoken!

Harold

[dbur]

I figured it would be some kind of fly or wasp larvae.

What's puzzling is there is no indication of anything have broken through the pupa case. Maybe they squeeze out through tiny holes I can't see.

I suppose this pupa is done for and I won't be getting any moth.

The flies can be a consolation prize, but I'll be in trouble if they get loose in the house.

[ChrisRaper]

In general a fly maggot will turn into a brown pupa while a wasp maggot will spin a silken cocoon ... usually mottled in colour. They will have broken out somewhere on the pupa but the chitin on the pupa might have closed back over?

It's highly unlikely that you'll get a moth now ... but the flies will be an interesting lesson in parasitoid/host ecology and knowing which species of fly attacks which species of moth is very useful too ... some very common tachinids have little or no host data.

Keep the puparia at cool room temperature and if any flies emerge give them a few days to fully inflate their wings ... any normal net cage will do. To kill them off the easiest thing to do is to put them in a freezer for a few hours ... humane and chemical free If you send them to me then I can have a go at identifying them. Genus is easy ... and I have friends who can perhaps help to get to species

[dunksargent]

I'm amazed that the moth pupa survived long enough to pupate if it had the parasites chomping away inside the larva. At what stage of its life would the moth larva/pupa have been impregnated with the parasite ova?

dunk

[ChrisRaper]

The attack strategy of the tachinid depends on what it is. Various strategies are used depending on the target host and the tachinid genus/tribe:

• - lay eggs directly on the host
  - stab the host with a piercing organ (note: they do not have hard ovipositors, unlike wasps) and push an egg in
  - lay newly-hatched larvae near to host larvae - the parasitoid larva locates the host and jumps on board before burrowing in
  - lay eggs on the host's foodplant, which are ingested and then hatch in the host's gut. Interestingly this explains how captive-bred moth larvae that have never seen a fly can end up parasitised ... because their foodplant was contaminated. A friend in Australia asked me last year how his Monarchs could have been attacked when they had always been indoors.

Hosts are usually the larvae or Lepidoptera or Coleoptera but can also be Hymenoptera (Sawflies), Orthoptera, Hemiptera, and even some ground-living Diptera etc.

Tachinids are not as host-specific as most of the wasp parasitoids and tend to attack related hosts in a selected range within a habitat ... i.e. "medium-large, hairy, exposed Lepidoptera larvae on heath". There are some host specific tachinids, though they are the exception that proves therule

[dbur]

How long should I be waiting for these tachinids to fully develop?

[rjlittlefield]

Speaking of ID's, I suspect the caterpillar was not quite a "tomato worm".

Judging from what I can see of the pupa, it looks more like a Big Poplar Sphinx Pachysphinx_occidentalis or some closely related species.

The most obvious difference is that the tomato sphinx pupa has a proboscis that stands out from the rest of the pupa. Google image search on Manduca quinquemaculata pupa to see what I mean about that.

I can't quite see the proboscis in the dorsal views here, but there are other differences in overall shape and surface texture that make me think Pachysphinx.

--Rik

[dbur]

This is what it looked like as best I can remember:
http://hsny.org/blog/2010/08/tomato-horn-worm.html

I was slothful and didn't get a photo while it was still a caterpillar so it may have had some minor variations. It definitely did have the pointy thing on the end though.

[rjlittlefield]

Or perhaps like this: http://bugguide.net/node/view/26809/bgimage.

--Rik

[dbur]

Or perhaps like this: http://bugguide.net/node/view/26809/bgimage.

--Rik

It actually looked more like the tomato horn worm than that.

[rjlittlefield]

A simple check is whether the pupal case has a separated proboscis like at http://insect-collector.blogspot.com/20 ... worms.html, or no obvious proboscis at all as at http://lepidoptera.jcmdi.com/m/sph/occi ... spupae.jpg. If it has a separated proboscis, it's not Pachysphinx, and if it doesn't, it's not a tomato worm (Manduca).

--Rik