A rare pure-white larva. What is it?

Asked November 16, 2015, 4:03 AM EST

A while gaggle of these larvae were eating on a tree in the mountain resort named Karuizawa, in Japan.
I have been unable to identify it.
I had trouble getting close enough to get better pics...

Outside United States insect identification garden insects tree insects and diseases

6 Responses

I am not an expert on the insects found in Japan, however, I strongly suspect the insects in your photos are a type of woolly sawfly in the genus Eriocampa (Family Tenthredinidae). Sawflies are actually a type of primitive Hymenopteran, and are related to bees and wasps. Their larvae look more like caterpillars and feed on the leaves of plants. A few types, especially those in the genus Eriocampa, secrete a coating of white waxy filamentsthat covers the body as a deterrent to predators and parasites. I was able to find a few scientific articles indicating that there are several species of Eriocampa sawflies found in Japan, but they didn't included photos. However, I have included a link below to a webpage which shows photos of one of the species of Eriocampa which we have here in the United States and you can see the similarity. If you know what the host plant is and do an internet search for sawflies on that host plant, you may be able to come up with a specific name for yours because many of the species are fairly host specific. It is also possible that this could be a sawfly in a different genus that also produces the waxy coating, but you would need an entomologist from Japan to confirm that possibility.

http://bugguide.net/node/view/32179/bgimage

Gary—As always, thanks for your good search efforts!
You are right: the photos of the Eriocampa are pretty similar to my 'whatever'.
That said, I would like to note that the white appendages on my worms seem to be denser and more uniform in presentation compared with the photos. Also, my worms were at least 2 inches long, which seems a bit large for bees, etc. If memory serves, the worms crawled along the stems quite rapidly. Overall, I think my worms would (did) make me think only of moth (or maybe butterfly) larvae, whereas the photos in the bugguide would make me scratch my head in considerable uncertainty and perplexity.
Sadly, I do not know trees very well and so cannot identify the one in my photo. Can you?
Also, I returned to the same site the following year (in the same season) to take more photos, but...the tree had been 'disappeared' and I found no others in the area.

Larry Stiver

Larry, Yes, you are right that the larvae in your photos don't look exactly like the photos I sent you which were of a sawfly species found in the US. I was not aware of any caterpillars of butterflies or moths that secrete a white waxy coating. However, after a little more searching on the internet, I discovered that there is a type of skipper butterfly caterpillar in India as well as at least one of the giant silk moths from SE Asia which have waxy filaments, so maybe a unusual caterpillar is still a possibility. The "filaments" on your larvae do look much more symmetrical, suggesting that perhaps there might be filamentous "appendages" of the exoskeleton underneath the white coating. That might be more typical of a caterpillar than of the sawfly larvae that I am familiar with. And yes, the 2" length would be a bit large for most sawfly larvae, but again I don't know what might be occurring over in Japan. Unfortunately, from your photos I can't see what the head capsule looks like or see how many prolegs these larvae have, either of which might help me determine if this is really a caterpillar or a sawfly larvae. These do not look like skipper or giant silk moth caterpillars, so if this actually is a type of caterpillar, it is something I am completely unfamiliar with. However, if it was a caterpillar, I would think there would be some kind of photos of it somewhere on the web, and I just cant find anything with my searches that matches yours. One other factor, most caterpillars tend to be solitary, while sawfly larvae often live gregariously. Since you have several larvae in close proximity in the photo, I still think it is more likely that these are some type of sawfly. But without better photos or actual specimens, I just can't give you a better identification.

Gary-
Would you be able to get someone to identify the tree? That might help ID the larvae, which most likely favors that tree. The tree was on the edge of a woods, but it may have been intentionally planted by the landscapers of the resort.

When I took the photos it was raining so I was holding an umbrella. I was also leaning over a railing on a boardwalk! Meanwhile 3 friends had gotten pretty far ahead of me and were looking progressively irked! Those are the reasons the photos are not sufficiently good for our investigative work! If I had known what a puzzle the larvae would end up being, I would have done a better job!

Again, if memory serves, there were about a dozen Snow Whites scattered around on the tree branches. They were solitary. I spotted them on the tree from 20 yards away (on a cloudy, rainy and thus rather dark day).

Anyway, thanks!

Larry S.

Larry, I am not a plant person, and I don't know anyone here at MSU who might be able to identify the tree from just a photo. As you indicated this might be some kind of ornamental tree that isn't even native to Japan. If it was an ornamental that was also planted here in the US, then maybe one of the plant people somewhere in the Ask-an-Expert system might know what it is. However, even if we knew what the tree was, that may not lead to us being able to identify what might feed on it. Unfortunately, I just don't have the resources here to identify foreign insects unless they are something common enough to show up in a book or on the internet. I think to solve this mystery, you are going to need to find an entomologist somewhere in Japan that can recognize this from the photo.

OK, Gary, I will see if I can find someone here (Japan).
Thanks for sticking with me for so long on this!

But I can't fully reassure you that you won't see my name on a new Question submission in the future!

Larry Stiver