Colorful silkworm caterpillars feeding on vegetation.
These coloful and spiky fellows are silkworms of the species Apatelodes pudefacta. The large, rather fluffy and spiky-winged adults are often mistaken for hawkmoths, and the tufted caterpillars can resemble tussock moth or dagger moth juveniles. In fact, the genus name “Apatelodes” literally means “looks like Apatela,” a reference to the old genus name for dagger moths. (“Apatela” later became “Acronicta.”)
This particular species gets two obscure references in its name. The species name “pudefacta” means “ashamed” and is likely a play on the related species “diffidens” meaning “diffident.”
The moral of the story is that scientists cannot be trusted to name things in non-confusing ways.
A luna moth caterpillar with an Argentinean peso for scale. For some reason this was the only coin I could find.
I wasn’t going to do another caterpillar post but I haven’t had a chance to key out the springtails for the other post I’m working on, so here you go. As you can see, they’re still growing like fiends. Also, I haven’t been to Argentina in two years; how is that peso still in my wallet?
Overnight all my caterpillars turned into evil masterminds. Or so it would appear. Just days before they all appeared to be perfectly innocuous little caterpillars who sometimes tried to chew off their siblings’ faces. But now just look at that caterpillar! He’s clearly up to something.
Someday soon I will be a beautiful butterfly.
I can’t find much in the literature on this reared-head posture–which appears to be pretty common in this family of caterpillars–but popular opinion around the internet seems to be that this is a defensive/camouflage posture to make the caterpillars look less like food to hungry predators. They do resemble little green twigs, although it’s kind of creepy when they’re all lined up in a row staring at you. It also puts them in a good position to employ another defensive response: clicking and puking!
A luna moth caterpillar in feeding posture on a partially eaten leaf.
When disturbed, late instar luna caterpillars and many other bombycoids (silk moths, hawk moths, emperor moths, etc.) make an audible “clicking”, “squeaking” or “crackling” noise with their mandibles and then regurgitate noxious chemicals. The regurgitant is apparently broadly deterrent to both vertebrate and invertebrate predators: in the kind of science experiment I love, Brown et. al (2007) demonstrated that both ants and mice reject food treated with caterpillar puke.
I haven’t heard mine click, but they have spewed brown goop all over when I change their leaves. I chose not to eat them, so it was apparently an effective deterrent for human predators as well.
>>The Luna Moth Saga
Newly hatched caterpillars.
The luna caterpillars are still rocking along so far. They eat like hungry hungry hippos so it’s a race to keep them well-foliated. I’ve been making lots of trips down the street for more walnut leaves. But how can you not love these sweet little faces?
Sweet little face.
Fun story: Today when I was snipping of bits of leaves to move the caterpillars to fresh foliage I accidentally snipped one caterpillar in half. (I did mention I’m terrible at caterpillars.) Anyway, the two nearest caterpillars immediately started chowing down on their dearly departed sibling like it was the best thing since bacon ice cream. Then, apparently, they got so carried away they started trying to eat each other, and for the first time in my life I got to break up a caterpillar fight.
I’m fuzzy like a teddy bear! And may also try to eat your face!
My caterpillars are a bit overcrowded at the moment, so I’m planning to spread them out across a few more containers. On the other hand, I suspect if I don’t they’ll take care of the issue for me.
First this quarter, next the WORLD.
>>The Luna Moth Saga
Acrobat ants (Crematogaster) suspending their caterpillar prey in a tree.
I spotted this impressive sight early this summer. A dozen or so acrobat ants gripped and suspended a huge caterpillar upside down from a tree branch above me, as other workers started to pick it apart. As arboreal ants, acrobat ants have some of the most impressive gripping ability I have encountered. I judge this by the time I have spent aspirating ants from trees for various projects for the lab–in particular the day I helped the post-doc collect several groups of 50 of these guys. These guys can really hold on. By the end of an hour I was light-headed from the aspiration attempts, and reduced to using the tube to try to pry the ants loose.
In fact, as Myrmecos author Alex Wild brought up a while back, a number of plants have adapted to take advantage of arboreal predators by providing wooly footholds to help them hold on.
A swallowtail caterpillar everting its osmeterium.
Here’s an immature form of the swallowtails we saw in the last post. Late instar swallowtail caterpillars like the one above have aposematic coloring, warning of the toxic chemicals they have gradually sequestered from the plants they eat. Swallowtail caterpillars also have another unique defense mechanism–an organ called the osmeterium, located in the head. When threatened, caterpillars evert the osmeterium, which resembles two brightly colored fleshy ‘horns’ on the caterpillar’s head. The osmeterium emits foul-smelling terpenes which, along with the startling appearance and the caterpillar’s thrashing movements, helps to ward off predators.
A tiger moth caterpillar climbs a grass stem.
When I was little I was always taught not to touch caterpillars because they might sting. ‘Especially the fuzzy ones.’ This training has survived in me and even today I am leery of the fuzzy variety of caterpillars, despite knowing that the stinging caterpillars are vastly in the minority and fairly distinctive. Luckily, friend and caterpillar expert Laura Ann was with me when I encountered this particular fuzzy fellow in the Welder Wildlife Refuge, so I not only had the opportunity to pet the little guy, but to try him out as a mustache and unibrow. He was a bit too active for either post. “Arctiids are fast,” Laura Ann pointed out helpfully, as my temporary unibrow made its escape.
A fuzzy black tiger moth caterpillar.
Tiger moths, family Arctiidae, take their name from the pattern common on many members’ wings, which often includes orange and black markings on a white background. These are relatively common visitors to light sheets here in Texas. Their caterpillars are often fuzzy, giving them the common name “wooly bears” or “wooly worms.” Like other caterpillars, its prolegs (the additional pseudo-legs it has as a larvae) are equipped with one or two rows of tiny curved hooks called crochets (see prolegs on the picture above). The hooks allow them to climb smooth surfaces like plant stems and leaves. The patterns and placement of these hooks are used for identifying many immature Lepidoptera.
An inchworm (family Geometridae) climbs flowers at the Welder Wildlife Refuge, in Texas
Inchworms (also called loopers and spanworms) are a type of caterpillar that take their name from their unique method of moving. Rather than crawl along leg by leg, these caterpillars have adapted to take advantage of the length of their bodies and “inch” along, contracting the front and back portion of their bodies. Even the placement of the prolegs (false extra appendages found in some insect larvae) has adapted to this behavior–inchworms lack prolegs in the middle of their body. Inchworms are typically colored in greens or browns to blend into their environment. Some, such as the caterpillar below, may have extra filaments to aid in their disguise. Caterpillars may strike poses to resemble twigs, stems, or even bird poop!
A filament bearing geometrid on a plant stem (Flynn, TX).
The “inchworm” style of movement has independently evolved in several lineages of caterpillars. However, by far the most abundant and diverse group are the caterpillars of the geometer moths, in the family Geometridae. This family name literally means “earth measurer” and these moths are often better known for their caterpillars than their adults.
Inchworm inching along.
Tent caterpillars in webbing (Sam Houston National Forest).
These gregarious caterpillars get their name from the elaborate ‘tents’ of webbing around they weave as a unit. There the young caterpillars dwell in relative safety, warming themselves early in the year, and escaping the high temperatures that may occur later in the year. The layers of webbing forming the ‘tent’ create a range of temperatures which allows the caterpillars to thermoregulate efficiently. Here you can see where the webbing has been torn open to reveal the mass of fuzzy orange caterpillars beneath. The caterpillars leave the tent to forage, laying down scent trails to find their way back and to alert tentmates to tasty finds. This behavior is remarkably similar to that of ants.
Tent caterpillars are members of the moth family Lasiocampidae. Adults are typically dull brown and somewhat fluffy.
An opened nest of tent caterpillars.