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Cockroach Larvae

Cockroach Larvae
Virginia Beach, Virginia, USA
March 27, 2008
Size: 1.5mm
I dissected the case and imaged some of the larvae within. This is a 100% crop of a 1:1 magnification image. The larvae are about 1.5mm in length.

Images of this individual: tag all
Cockroach Ootheca Cockroach Larvae


Moved from Ants, Bees, Wasps and Sawflies.
Yes, I think so. Chalcidoidea may even be safe... Eulophidae or Pteromalidae are the possibilities I know of. Evaniids would have just one larva per ootheca. There are egg parasitoids in Platygastridae too, though, so this is probably a good placement for now.


I wonder if it is safe to move them to Parasitic Apocrita, at least, if we don't know anything else.
I am glad that they got moved out of cockroaches.

So almost three years later...
I was looking for another cockroach and stumbled across this conversation again!

So I know for a fact these are not cockroach larvae and found some amazing images in the paper "The Biology of the Cockroach Egg Parasite, Tetrastichus hagenowii (Hymenoptera:Eulophidae)" by Louis M. Roth and Edwin R. Willis. These images look a lot like what we have here and the paper states that this parasitoid is known in the southern and eastern United States.

Does anyone know a way I can add the image to the comments here so you can all see it? I just saved it as a JPEG on my computer. I am no good at these things. Otherwise I guess I could upload it somehwere on bugguide and then refer to it as long as I cite the correct source.

Cockroach larvae?
I found a very young snake 5 inches in my pool and put it in an empty gatorade bottle. The next day i caught a large cockroach and put it in the bottle dead so the snake would have something to eat. The sanake ate the roach except casing and wings. Did the same a couple days later and the snake ate that one too. Today the snake is dead with dozens of larvae? crawling around the snake and throughout the plastic bottle. Some of the larvae are white 1.5mm with a dark spot that moves along the length of its body when the larvae moves. The other larvae? Are somewhat smaller with a dark oblong blob and a faint spot that moves like that in the white ones. My guess is the larvae ate there way out of the snake. Comments are welcome.

It would be best if you could submit a picture.
Cockroach nymphs do not look anything like this, they are just smaller than the adults, and wingless. These larvae are wasp parasitoids of the cockroach ootheca, and ate the cockroach eggs. I don't know of any parasites of snakes that would eat their way out like that, but if the snake died (if you left it in the bottle outside it's likely to get very hot and not very good air exchange, which could be why it died, also depending on how big the cockroaches were, the cockroach exoskeleton may have perforated the digestive tract along the way) maggots would come fairly quickly and begin to feed on it. The way you describe the dark spot moving as the larva moves does sound like a maggot.

There may be copyright issues loading the image here (or anywhere) without the copyright owner's permission, but maybe loading it and then immediately frassing it would be OK? It would give a 30 day viewing period.

Yeah I was worried about that too.
It is published in Transactions of the American Entomological Society and available online for me (Through the UW) on JSTOR so I didn't know if it'd be ok to post it as long as I cite it or how that would work.

you either need the copyright owner's permission (either directly or though something clearly stated like a Creative Commons license) or you have to wait for it to fall into the public domain.

Well it was published in 1954
So I'm not even sure if the two authors are still alive or not! Let alone who holds the copyright...

Oh well, I showed this to our professor Dan Young and he said they are for sure Hymenoptera larvae. He doesn't know which, he isn't familiar with the parasitoids of cockroach ootheca, but there are several.

Moved from Cockroaches.

Embryonal stage...
Or parasitized egg-case? I think Cockroaches have a direct development, i.e. small "baby -cockroaches" hatch from eggs instead of these grub-like larvae.

Not cockroaches
Cockroach immatures look nothing like this, they're just nymphs which look like small adults. Here's a good example of what roaches look like at hatching :

This is definitely some sort of parasitoid, looks like a fly.

Did you see
Richard's comment below? These aren't hatchlings, the case was opened while they were still developing, so the question is whether they can look like this before they're ready to hatch. The fact that they were lined up in neat rows, like sardines, without any evidence of munched pre-cockroaches, suggests to me that these are in fact the immature cockroaches, but if you have contrary information on cockroach development, please let us know.

I see spiricles
If you look at the larva all the way on the right, there is a small brown crescent towards the bottom of the picture. I believe that is a spiricle. I also think I can see another in the anal opening, which is called amphipneustic, which is a character of many tachinid larvae. Eggs wouldn't have that. Also, were they moving when the case was opened? From the oothecae I've dissected the eggs didn't move or wiggle, although they were lined up as described. I would also think the dark material inside the larvae would be cockroach digesting. I didn't mean to ignore Richard's comment, I just really think this was a parasitized case, which is very interesting!

When opened, these larva were lined up like rows of sardines. I thought they were the developing baby roaches.

Maybe you're right
The darker "cores" inside the grubs could well be the future babies. But that would mean there is an intermediate stage between egg and 1rst instar nymph, which I ignored.
Indeed, there is often a so-called "primary larva" stage among hemimetabolous Insects, like e.g. Odonata.
Maybe the story goes the same for Cockroaches and Mantids. I'll try to find precise info about the topic.

Then, the correct word would be embryo I guess, if these are in fact cockroach embryos. Would embryos look segmented like these ones? Hard to believe.
We don't even know for sure whether the egg case is a roach ootheca or something else. It doesn't look like the ones I have seen. What other bug could it be?

Definitely a cockroach ootheca
I will say with absolute certainty (a rare thing) that this is a cockroach ootheca. It looks rather different from the ootheca of the German cockroach, which the female carries around until her young hatch, but it is quite typical of cockroach oothecae in general. It's also typical for the female to cover them with debris as this one was.

How many
of these larvae were there? From what I've read there would be ~10-25 cockroach eggs in an ootheca. The evaniid wasps parasitize cockroach oothecae, but there should be only one larva per ootheca. I'd be interested to know what else might emerge from one of these...

There were...
at least two dozen lined up in there (a dozen or so in each half est.). I wish I could have done a clean split of the two halves, but it didn't work out that way.

Definitely a disguised cockro
Definitely a disguised cockroach ootheca. The little guys inside are partially developed cockroaches. They would be lined up in two rows as you describe. If the young hope to get out of the ootheca, they must mature at the same time expand by swallowing air, and jointly pop open the seam. The ootheca will open like a purse and the young scramble out after which the ootheca snaps closed again. Anyone underdeveloped or not quick enough remains sealed inside and dies.

Do you have a reference? We could add this to the guide page if you can give us the reference. Please.

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