Location: Arcata,Ca USA: N 40.86652 and W -124.08284
February 10, 2011 12:15 am
I want to register on your sight but hitting the register button redirects me to the log in page again – I’ve tried it for a few days now. Am I missing something or are you having a problem? I love insects and the philosophy of your sight – I have a lot of photos and some stories – I can even donate something . Why am I denied WTB? Included here are some photos of the I found this cocoon on one branch and thought some cruel wasp had laid eggs on it. From what I can tell it is a cocoon of the Rusty Tussock Moth (Lymantriidae: Orgyia antiqua) Just guessing at the species but it seems a trademark for the genus. The female lays eggs on her own cocoon after emerging and mating. She is flightless apparently. She must just sit tight and use a pheromone to attract a male. I hope the host plum will manage to weather both its early blooming and the hungry caterpillars that start munching away when spring really does come
First, let us apologize on two counts. First the delay in a response is due to our limited staff. We are unable to even read all the requests we receive, and when we are very busy we tend to select emails based on the subject lines. The subject line on your email did not immediately catch our eye. Additionally, the editorial staff at What’s That Bug? is distinct from the technical staff. We have an ace webmaster who does not answer any identification requests, and the editorial staff is quite inept at dealing with any website technicalities. We will promptly forward your registration problem to the webmaster in the hope that he can guide you through the technical problems you are experiencing. Now that we have finished begging for your forgiveness, we need to tell you we are positively thrilled to post your images of Tussock Moth Eggs from the genus Orgyia. We would not be able to positively provide a species identification, and we wonder how you arrived at the Rusty Tussock Moth, a European immigrant, as the correct species. Other members of the genus Orgyia have a similar method of laying eggs. We are linking to a FlickR posting of an adult female Rusty Tussock Moth shortly after laying her eggs, and BugGuide has photos of other members of the genus. Though we do not think it is possible to provide a conclusive identification for your eggs, we would not eliminate the possibility that they belong to the Western Tussock Moth, Orgyia vetusta, which BugGuide does report from California. The Rusty Tussock Moth has been reported from Oregon on BugGuide, which indicates the common name Vapourer for the species, though that common name seems to be accurate for the entire genus. BugGuide also provides this information: “Caterpillars are generalist feeders on the foliage of flowering trees in the Rosaceae, Fagaceae, Ericaceae, and Salicaceae.” Plum is in the family Rosaceae, so your identification is entirely possible.
Update from Rueka
Absolutely no problem on the delay, I hardly felt there was one. It is wonderful to get a response at all and I am most happy for yours. Such detail and such an interest, and curiosity, in the little moth eggs I found, so much more gratifying than, ” Oh that’s kinda gross. What if they hatch or something?” What is “or something” I wonder? Are caterpillars ominous beings? Am I blind to some lurking danger? Ok, yes there is “Tussockosis” I suppose but I am not planning on eating them or rubbing them in my eyes. I just can’t see putting this very high on my list of things to fear in the world. Now if I were a tree perhaps I would be a little more afraid of them. As I am not a tree however, I really hope they do hatch so I can photograph that too and maybe get a more precise narrowing to species. The common names for so many of these Orgyians are a complete mess so I am going to avoid them now. I must admit to having guessed as far as Orgyia antigua goes, the result of a few quick searches (possibly similar to yours) in Wikipedia and Bug Guide and maybe some other places where I compared the assumed range, and feeding habits, and my photographs to theirs. The photos I found of O. antigua (eggs) looked “dead on” compared to mine and my ignorance of this behavior filled in the blanks. The host plant families (as you noted) seemed to match for O. antigua and rosaceae. Perhaps my identification to species was a bit hasty based on so little. However, There are at least three others in the genus Orgyia common here in N.W. California. One of my books, California Insects (Powell & Hogue, 1976), states that O,vetusta is (or was) restricted to sea coast dune habitats while a much more common (literally garden variety) O. gulosa (often mistaken for O.vetusta) has a wider range. I am not finding what O. gulosa eats and, at the moment of writing this, I have no internet to reference ( how did we all make it so far before the internet?). Powell and Hogue, unfortunately, do not mention the common host plants for O. vetusta either. My eggs were about 2km inland and in town. Alternately, I can’t ignore O. pseudotsugata who may, or may not, be limited (as larvae) to cocooning on conifers ( Insects of the Pacific North West Haggard &Haggard 2006). This one might be the true “native” but seems the least likely to lay eggs on a plum tree. Yet, the conifer forests are closer than the dunes by a hair and a leaf. I wonder if they (the caterpillars) travel by silk balloon? What fun that would be. The Insects of the Pacific Northwest does not even mention O.vetusta or O. gulosa but notes O.antigua as being “very common” in costal areas et.al. and provides an eerily familiar looking photo of a cluster of cocoon nested eggs. I am glad that we all seem to have an easy way to agree on the genus anyway. So, all that said, my money is still on O. antigua as the most likely depositor of these lovely cyclopian orbs; especially, considering the hapless plum picked by mum for her progeny to feed upon. Although I am still,clearly, guessing and maybe a little reluctant to let go of my half baked initial ID. I think that all we can do is wait to see if they make it through the winter and hope that something identifiable emerges that doesn’t disperse itself while I’m sleeping or out stumbling upon, and being distracted, by some other arthropodic curiosity.
Thanks so much for your interest, and for hosting such a wonderfully entertaining and informative website full of great “bugs”.
Thanks for the update Rueka. We have one additional thought regarding dispersion of the caterpillars. A caterpillar that is hatched from an egg that was laid on the food plant would have no need to balloon away to another location that might not have any suitable food. Spiders often balloon away from the site of hatching, but they are predators. We can’t help but to be reminded of that old adage “The fruit doesn’t fall far from the tree” when it comes to these Tussock Moths. The female is flightless and cannot fly to a new location, so her eggs will be laid upon the same plant that she fed upon before her metamorphosis. One begins to wonder how a species with flightless females can ever manage to change its range or location with such limited mobility.
Daniel and co.
I apologize for the reference to ballooning. My tongue was a little in my cheek there on that. I was waxing romantic. Your question regarding the motility of the female is a good one and stumped me a bit too while I thought of all this until I connected it to the Tussock moth “epidemics” that sporadically occur in western coniferous forests. This is well documented and occurs specifically with O. pseudotsugata and related sub-species. I need not look this up. I have seen it. I had just almost forgotten. The caterpillars literally drop from the trees and travel en-mass over the ground presumably in search of more trees. I think most caterpillars avoid this out of fear of predation but most of the Orgyia are apparently toxic so are left alone by savvy predators. I would conjecture that they leave the tree they hatch from when the food supply becomes scarce as a result of their over whelming numbers. But as the female is flightless it could also be an innate strategy to drop and crawl along looking for better pastures before metamorphosing. Of course in most cases when the populations are balanced and there is plenty of food the female would have no reason to leave the tree unless she just felt genetically driven to move on. I would be surprised if my little eggs are O. pseudotsugata though just because they are in a plum, but I wouldn’t rule it out entirely either. I think the caterpillars will seek out any high place during their final instar and make a cocoon regardless of food sources. I’ve seen them wedged in cracks in walls of concrete after an “epidemic”. However that was long ago and in mountains east of here. It was the eggs I had not seen before – or had not noticed. I’m so glad I found them. It has been a nice distraction to figure it out and piece it together a little. I still get to look forward to actually identifying these guys after they hatch. Thanks for the insights. I’ll be sure to let you know what happens.