Category Archives: Acronicta

Inflated caterpillars

There are several ways to preserve caterpillars for study. You can boil them and drop them into a jar of alcohol, you can freeze dry them, or you can inflate them.

Inflate them?

Yes indeed.

The photos in this post are all of inflated caterpillars, in the genus Acronicta, found at the Cornell University Insect Collection (CUIC).

CUIC_Acronicta_albarufa (1) copy

Acronicta albarufa

Inflating (or “blowing”) caterpillars is a traditional technique that is no longer taught or commonly used, however it can produce fabulous results. The caterpillar remains dry and can be kept in a drawer along with adults, which makes them easier to study than specimens in alcohol. Their external features are usually well maintained – specimens from the early 1900s don’t look much different from modern specimens.

However they are lacking their internal organs, and the last couple of segments are destroyed in the preparation process. The technique is also quite labor intensive and requires unusual equipment. So how does it work?

CUIC_Forbes_Acronicta_aceris (4) copy

Acronicta aceris

I have talked to a few entomologists who have inflated caterpillars, but not since their undergraduate or graduate school days. I have found a few resources which describe the process. Here is a description from the University of Minnesota Agricultural Experiment Station:

Basically you cut a slit into the posterior end of the caterpillar, and using a pencil, roll out the guts (starting at the head end). You must be careful to not destroy the hairs and other features of the exterior. Then you insert a glass tube and inflate the caterpillar, and keep the caterpillar inflated as you heat it in a small make-shift oven. One colleague described using a coffee can over a bunsen burner for this purpose.

Once the caterpillar is dry, the glass tube is removed and the caterpillar can be prepared for pinning. Either a wire or stick can be inserted, or the caterpillar can be glued onto the wire or stick by its prolegs underneath the body.

CUIC_Forbes_Acronicta_americana (1) copy

A box of Acronicta americana adults, caterpillars, and pupae

From the photo above you can see that even caterpillars with lots of hairs can undergo this technique. In fact, they look incredibly lifelike.
CUIC_Forbes_Acronicta_morula (6) copy

Late (above) and early (below) instars of Acronicta morula

Another benefit of inflating caterpillars is that the body shapes are extended and not distorted by being kept in a liquid. The important bumps and hair positions are kept as their were in life. However the body may be a bit overextended depending on how well it was squished and inflated.

CUIC_Forbes_Acronicta_psi (6) copy

Acronicta psi

One reason I particularly enjoy the inflated caterpillars is that they are easy to transport and trade – so there are many European species in collections here in the USA. Caterpillars are not often kept in collections to begin with, so to have these specimens available to me for study is quite exciting.

As you can probably guess, I’m going to set up my very own caterpillar inflating oven as soon as I can! And I’ll have another post soon on even more inflated caterpillars I have found at other collections.

Sources: _____________________________________
University of Minnesota, 1908. 16th Annual Report of the Agricultural Experiment Station. Bulletin #105. How to Collect and Preserve Insects. Pages 119-146.

I warned you

Aaaand we’re off – to see if some of my caterpillars are chemically protected.

This is my arm right now:

I’m about to go rub some caterpillars on another lab member.
(It’s ok, we’ve filled out the human testing protocol paperwork.)

So far I’m intrigued that these three species have all given me the same type of reaction in terms of timing, appearance, and sensation (it burns, and then itches). Other people in the lab have reacted to them as well, but I want to document this in a systematic fashion. It could be an important phylogenetic character. So far we’re pretty sure two of them are in the same clade, and the other we are going to add to our molecular dataset soon.

For science!

Here I am with some caterpillars (Acronicta impleta)… that I am about to start testing for chemical defenses by rubbing them on my arm. From a few reactions I’ve had, it seems there is one clade within the genus Acronicta which are chemically protected. I am still sporting a rash from a caterpillar I rubbed on my arm a week ago. For science!

CaterpillarArts

I am so excited!!!

I just purchased a custom order from CaterpillarArts on Etsy. She opened up her shop a week ago, featuring beautiful little caterpillar pendants. When I saw her work I had to ask for my favorite species, Acronicta funeralis. I know it’s a tricky one, but AJ blew me away with how accurately she was able to re-create this caterpillar.

I can’t wait to get this little guy in the mail next week!

For comparison, here is a photo I took of a real Acronicta funeralis last summer:

Please check out her shop, more goodies are being added frequently – I just saw she has a few crystalids as well!

Word of the day: Hypognathous

(The word of the day is taken from the Torre-Bueno Glossary of Entomology)

Hypognathous, having the head vertical and the mouth directed ventrad, e.g., most exophagous Lepidoptera and Hymenoptera larvae

Like this!

Acronicta falcula

Puddling

Here is a story about a rather desperate moth.

I have a number of female moths in the lab which I am hoping to get eggs out of. As I checked them today, I realized one of my Acronicta americana was actually a male. Not sure what to do with him, I put him on my friend’s shirt to hang out a while before being released.

Back in my office a few minutes later, I heard a yelp from the lab. I walked over to see the moth climbing on my friend’s beard, probing him with its proboscis. Then it went straight for his mouth!

Moths and butterflies have a behavior called “puddling”. Males (some females do this as well) will suck up liquids to gain nutrients such as sodium. Butterflies and moths can be observed puddling around puddles, ponds, mud, dung, damp concrete… and apparently, some are also attracted to saliva. Males are the usual suspects because they will offer these extra nutrients to females as a sort of nuptial gift along with their spermatophore during mating.

This moth was fed sugar water while in his enclosure, but apparently the allure of sweat and saliva were too much to resist.

Here is a video, to show just how excited this moth was:
I wonder if other moth species would lap up human saliva so eagerly? I am not sure anyone in the lab is going to jump up and volunteer for that study.

I’ve been looking for you

I was really hoping to get Acronicta hasta eggs this summer. I missed the first brood, but there should be another round of mating/egg laying this summer. That’s the nice thing about Acronicta, most of them have two broods per year. It’s a nice safety net if I mess up the early spring window for collecting.

Two weeks ago we came across this big guy… Acronicta hasta. There is no way this species should be in its final instar already! The female must have emerged in April when we had some of those crazy warm days… and somehow the caterpillars managed to survive a long stretch of cold nights with only a little vegetation starting to grow.This might explain why some species were hard to get this spring – the strange weather threw off a lot of insect life cycles.

The early instars are all green with a red stripe down their back. They sit on the upper surface of leaves, flaunting themselves to birds. It is not know if they are chemically defended, or if the red stripe serves as aposematic warning coloration. They feed on cherry, which is not exactly a poisonous plant. This is why I would love to experiment with them! A study by Singer et al. (in press) has shown that birds tend to leave this species alone.

The last instar, however, is black with yellow spots and a maroon red stripe down its back. It prefers to rest on twigs or bark, as seen in this photo (this was its natural resting position when we found it):

And here it is in the sunlight:

Since this species burrows into wood to pupate, it makes sense that they would don a darker appearance – you probably do not want to be a bright green caterpillar on bark. If they are really only bluffing with their red warning stripe, it would be a good idea to try hiding some of the time.

Babies

I have been inundated with hatchling caterpillars… ahh, this is how life should be. My favorite part of entomology is catching and caring for the insects themselves. For the past week I have been rearing a few species in the lab, but some of the clutches were so large I had to transfer them to sleeved branches outside. If you keep too many caterpillars together, they are more prone to disease. Last year I lost many caterpillars to something I called the “butt sickness”… we do not know if it was a bacteria or virus, but it caused intestinal issues until they perished. The butt sickness spread through a few dozen of my caterpillars. Poor little guys. I don’t want that to happen again!

Also, feeding caterpillars picked leaves (as opposed to rearing them on living plants) stunts their growth. This has been documented in books and passed along through anecdotes, but I am not sure if it has been systematically studied. I do know that many of my adults emerging now, which I reared last summer in the lab, are much smaller than wild caught specimens. We would prefer to get healthy, normal sized adults for our collection.

Of the caterpillars I am putting outside in netting, some will stay there until they are ready to pupate and I will simply observe them through the netting. I am interested in whether they rest on the upper or under side of the leaf, if they change their habits depending on the time of day, and whether their behaviors change when they change colors.

Others will be removed once they are larger to use in bird predation experiments. I have a meeting with a collaborator from another university tomorrow to get equipment for that.

Here are some of my little darlings. This species is Acronict lobeliae. It goes through several color/pattern changes throughout its life as a caterpillar. This is the second instar.

Here I am moving some caterpillars to their new enclosure outside. I call these my “poodles” because of their fluffy end segments. They are actually Acronicta impleta. You can sort of see them… the black fuzzy specks that are about 4mm long…

Some of the sleeves all set up.

And my sign! Hopefully nobody will mess with my set ups. I have some sleeved caterpillars in a few locations, some more secretive and one smack dab in the middle of campus.

This is my first time rearing caterpillars outside, so I am hoping everything goes smoothly. I have more eggs waiting to hatch, and more eggs are on their way from a collaborator. I am going to be doing much more serious blacklighting this week and next week, hoping to get some more females.

Word of the day: Multisetiferous

(The word of the day is a random word on a random page of the Torre-Bueno Glossary of Entomology)

Multisetiferous, bearing many setae

Setae are sclerotized hairlike projections of the cuticle. People often use the words “setae” and “hairs” interchangeably. Caterpillars have two types of setae: primary and secondary. The primary setae are mostly homologous (shared) across lepidopteran families. Each setae is named with a letter and number related to its position on the body. For example D1 is dorsal setae #1. Any differences in the number or arrangement of primary setae can be useful in diagnosing the family, genus, or species of a caterpillar. Secondary setae are only present in a few groups, the ones which tend to be exceptionally hairy. Thus, a wooly bear would be deemed multisetiferous.

Some of my Acronicta species are multisetiferous, like this fuzzy Acronicta americana. Just look at those tufts!

Word of the day: Exuviate

(The word of the day is a random word on a random page of the Torre-Bueno Glossary of Entomology)

Exuviate, to undergo ecdysis; see moulting

Watch out, that caterpillar is about to exuviate!
A variation of the word is exuviation, another word for ecdysis.

Apparently there are a lot of ways to describe the fact that immature insects go through molts in order to grow.
The resulting cast-off skins are called exuviae.
There are also related exuvial droplets and fluid to aid in the molting process, exuvial glands, and exuvial space (the space between the new and old skins during molting).

I dug through my photos and found this cutie, Acronicta afflicta, next to his exuviae. Most caterpillars build a molting mat out of silk, produced by silk glands on their head, that they can grab onto. They dig their little crochet hooks (found on the prolegs) into the silk and use that grip as leverage to get out of their old skin. If you disturb them during this process you may accidentally rip them apart (they have a strong grip!) or otherwise disrupt the molting process. This gets to be tricky when we are rearing lots of caterpillars and need to transfer them to new foliage, so we often cut out the small piece of leaf they are on and transfer them that way.

Ryerson Lab

Functional Morphology, Sensory Biology, Behavior, Biomechanics

I spell it nature

Trying to make sense of the world through science and language.