Can you help identify these Caterpillars
Sat, May 23, 2009 at 8:33 PM
Dear Bugman,
I recently found a silk nest filled with these black-brown caterpillars. They have rusty hair covering their bodies and have distinctive white and orange markings. The orange markings in a triangular shape and there are 2 to each segment of their bodies. the white markings are found along their sides as well as down the top of their bodies between the orange markings. Several people have said they could be Painted Ladies, yet they really don’t resemble any pictures I have found.
Thank you for your help
Penny
Kelowna British Columbia, Canada
Western Tent Caterpillars in Captivity
Dear Penny,
We regret to inform you that these are not Painted Lady Caterpillars, nor any other lovely butterfly, but rather, they are Western Tent Caterpillars, Malacosoma californicum, which can be viewed on BugGuide. The larvae are social and gregarious feeders that construct silken nests for protection when not feeding. Here is what the Washington State University Biology and Control of Tent Caterpillars website indicates: “The western tent caterpillar ( Malacosoma californicum pluviale Dyar) is often the most numerous in western Washington. Its orange and black markings are familiar to many people. This species spins tents on the tips of branches. The eggs hatch in early spring just as the new buds break in April or May. The young larvae begin feeding in groups. The larvae of both species molt (shed their skins) four times during their 5- to 6-week growing period.
As the caterpillars mature, they begin to feed in small groups or singly. Just before they spin their cocoons in mid-June, they crawl about looking for a protected place in plants or on structures to attach their cocoons. The adult moths emerge in approximately 7 to 10 days. The moths are stout-bodied and light brown. They often fly in clusters around street or porch lights on summer evenings. After the moths mate, the females lay 100 to 350 eggs in a froth-covered band around small twigs or branches of host trees. The eggs mature in 3 weeks but do not hatch until the following spring.
Tent caterpillars are primarily a nuisance. They do not transmit diseases to humans, do not bite, and are not poisonous. During years when large numbers of these caterpillars hatch, they can cause slippery roads and walks when they leave the trees.
Benefits of a caterpillar outbreak can be numerous in a natural setting. While caterpillars are distasteful to most birds, some birds feed on them. When alders and other trees are defoliated, the shrubs and trees below receive increased sunlight, giving some of them a boost in growth. The eaten leaves pass through the caterpillar’s body and emerge as little pellets which can break down easily, returning nutrients to the forest floor. Pupae provide nutritious meals for small mammals, and moths are eaten by birds and bats.
Where trees are crowded or stressed, the defoliation could be a life and death matter. Weak trees may die; healthy trees will leaf out again. In a natural setting, surviving trees can prosper in the absence of competition.
Healthy ornamental trees and shrubs should survive even serious defoliation. Trees which have been under stress (excess cold, heat, crowding, drought, flooding, etc.) may succumb and require more protection.
Natural Enemies
Tent caterpillars have numerous enemies. One is a tachinid fly which parasitizes the larvae by depositing white eggs on the caterpillar’s body. When the egg hatches, a small maggot burrows into the caterpillar and begins feeding. Tent caterpillars are also subject to a virus disease called wilt. While such natural enemies will reduce the number of tent caterpillars eventually, this process is gradual and may take 2 or more years. During that time, the affected trees may suffer such severe damage, that they will not recover. ”
Western Tent Caterpillars
¶ Posted 24 May 2009 § ‡ ° underwing caterpillars?
Dear Bugman,
We LOVE your site and use it regularly. We also have it linked on our greenhouse/nursery website to encourage our customers to i.d. and learn about bugs rather than freaking out, pouring chemicals on them and otherwise engaging in Unnecessary Carnage. Your site is a fantastic resource — educational and entertaining! So anyhoo, the lumps on this pin oak tree were spotted this afternoon by one of our fellow treehuggers. Upon closer examination, we all had to rub our eyes a couple of times to be sure we weren’t seeing things and confirmed that they were two pinky finger-sized caterpillars perfectly matched to the smooth gray bark of the immature pin oak. When they were still they looked just like part of the tree trunk, and we had to touch them before they began slowly making their way down to the bottom of the trunk headfirst. They had a soft fringe all the way around their bodies — I wish my photo was clearer. They were the coolest dang bugs I’ve seen in a long time. The closest thing I can find on your site is an underwing caterpillar, but the one you have matches a corkier bark. Are their different species that match different trees? Oh yeah, we’re a few miles south of Lawrence, Kansas, as the moth flies. If you can help us out between photograms, we’d be much obliged. Your friend,
Plantlady
Dear Plantlady,
We agree with your assessment that these well camouflaged caterpillars are Underwing Caterpillars in the genus Catocala, but we are at a loss for the exact species. BugGuide has over twenty images of Underwing Caterpillars posted.
Correction: (06/29/2008)
Daniel:
The pair of “underwing caterpillars” are actually two larvae of the “large tolype” moth, Tolype velleda. Very striking, aren’t they!
Eric Eaton
¶ Posted 28 June 2008 § ‡ ° Eastern Tent Caterpillars
Here is a picture I took while hiking along the C&O canal in Maryland. These things are EVERYWHERE and until I took a look at your site, I thought they were Gypsy Moth Caterpillars. My 4 year old son and I were at the National Zoo the other day and while the elephants couldn’t hold his attention, he was facinated by these caterpillars inching along all over the place. He then collected several and gently placed them on his shirt and then proceeded to strut around the zoo covered in them like some caterpillar tamer on Animal Planet. Alas, I did not have my camera with me that day. Thanks for the great site!
Tracy
Hi Tracy,
Thanks for your touching story. We have recently received several images of individual Eastern Tent Caterpillars, Malacosoma americanum, but we have not posted them. Your photo is a textbook example for identification purposes.
¶ Posted 08 May 2008 § ‡ ° Tent caterpillars
and a closeup….This was taken near a child’s park in Asbury, NJ on Mother’s Day 2007. I found this about them on Wiki “Tent caterpillars are moderately sized caterpillars in the genus Malacosoma in the moth family Lasiocampidae. Species occur in North America, Mexico, and Eurasia. Twenty-six species have been described, six of which occur in North America. Some species are considered to have subspecies as well. Although most people consider tent caterpillars only as pests due to their habit of defoliating trees, they are among the most social of all caterpillars and exhibit many noteworthy behaviors. Tent caterpillars are readily recognized because they are social, colorful, day active and build conspicuous silk tents in the branches of host trees. Some species, such as the eastern tent caterpillar, Malacosoma americanum, build a single large tent which is typically occupied through the whole of the larval stage while others build a series of small tents that are sequentially abandoned. The forest tent caterpillar, Malacosoma disstria, is exceptional in that the larvae build no tent at all, aggregating instead on silken mats that they spin on the leaves or bark of trees. Tents facilitate aggregation and serve as focal sites of thermal regulatory behavior. They also serve as communication centers where caterpillars are alerted to the discovery of new food finds, as discussed below.”
Debbie
Hi Debbie,
Thanks for sending us your photos and providing the factual information.
¶ Posted 13 May 2007 § ‡ ° We saw lots and lots of nests of these worms in the nooks of small trees at Bear Mountain NY. We didn’t notice them until the peaks which are around 1000 ft in altitude. They may have been at lower altitudes but we didn’t notice them there as much. Any idea what this insect is? We assumed it spins the nest so it’s maybe related to silk worms?
Ted
Hi Ted,
This is the tent of the Eastern Tent Caterpillar, Malacosoma americanum. The female lays eggs on tree branches in the fall and the egg overwinter, hatching in the spring. The caterpillars are social and spin the tent for protection.
¶ Posted 07 May 2007 § ‡ ° Hello again from the Yucatan of Mexico
You helped me with a lovely (and pesky) melon moth a month or so ago and now I have a new question. The attached photos show a woolly caterpillar that has a hard and shiny reddish head. One photo shows how they gather at the base of trees during the daytime. At night they climb the local trees – one they seem to like a lot is a wild fig – and eat the leaves until they look like lacework. Then, as the sun comes up they stream down the tree trunks to gather in hollows and under logs. They are really doing a number on the trees and if they are going to hatch into something noxious I may consider spraying them to reduce their numbers near the area where we live. We live in a dense jungle so won’t be anything close to eliminating them overall. Another characteristic is that they sometimes have a spiderweb-like thread that they emit. I googled the description but don’t find anything. I have looked at all of you photos and don’t see one that looks quite like it nor any description of the behavior. Can you help?
Kathe Kirkbride
Hi Kathe,
Your written description and photos indicate this is probably some type of Tent Caterpillar, though many do not form tents. Huge aggregations often do considerable damage, but these large numbers are cyclical and do not occur every year. Loosing leaves is not a life threatening situation for trees. Poison might do more harm than good.
¶ Posted 24 December 2005 § ‡ ° Can you help?
Every year in August in Michigan( all through michigan), I see this web like mass in trees. I asked the locals, they had no clue what they were, they didn’t even notice them. Do you know what it is?
Yvette
Hi Yvette,
This is a Fall Webworm, Hyphantria cunea, nest. In the fall, these social caterpillars can build enormous webs that cover the leaves. Here is a site with more information.
¶ Posted 23 October 2005 § ‡ ° rockin’ caterpillars
These little fellows were twitching in their mass cocoon. The picture was taken in early summer. Can you identify them?
Mike
Boise, ID
Hi Mike,
These are Tent Caterpillars, probably Eastern Tent Caterpillar, Malacosoma americanum. Here is a link with additional information.
¶ Posted 23 September 2005 § ‡ ° 
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