Funny Larvae

Firefly larva © Corey Kallstrom

Who would think that insect larvae can be interesting? They don't have much to offer when compared to their adult counterparts. We can't help but notice adult insects. They fly, they buzz; in fact they can make quite a racket during hot summer nights. Some blink their little green lights over the meadows. Others wear flamboyant colors that seem like works of art.

Glowworm (Phengodes sp.) © Ashley Bradford

Larvae, on the other hand, at least most of them, lead obscure, secluded lives, hiding in secret places. They are rather colorless and shapeless worm-like things, with stubby little legs or no legs at all, with tiny eyes or no eyes at all. None of this is surprising. Larvae have only one function in life, eating and growing bigger. They have nothing to do with the more exciting things like sex. That is left for the adults. Well, larvae actually have two functions. They possess strategies for fighting or evading enemies. Despite such dull lives some insect larvae manage to be quite interesting.

Lightning bug larvae have green lights along their bodies. They look like little trains, and that is what we call them in Argentina, trencitos. One wonders about the purpose of these lights. Adults use theirs to attract members of the opposite sex, but larvae have nothing to do with that. These lights must serve another purpose. It turns out that lightning bugs are highly toxic and bad tasting, so the lights are telling predators to stay away and avoid the unpleasantness.

Monarch caterpillar

© Beatriz Moisset

Some caterpillars use the same strategy. The monarch butterfly caterpillar wears bright black, yellow and white colors arranged in a bold pattern to advertise its toxicity obtained from feeding on milkweeds. Other caterpillars have a variant of this method. The eastern swallowtail butterfly is large and colorful with a pattern of black and yellow. The larvae change their appearance dramatically as they age. The nearly fully grown caterpillar is bright greenish yellow with two large eyes on its head, except that these are not real eyes but just look like them. It is thought that this feature serves to deter predators that erroneously assume that they are dealing with a larger and more powerful creature at the sight of these large eyes. They have another feature for defense against enemies. When threatened, they pop up two bright antenna-like threads. These appendages emit a nasty smell that seems to be effective in keeping other creatures away.

Eastern swallowtail butterfly caterpillar.

Showing its osmateria when threatened

© Beatriz Moisset

Some larvae feed on extremely poor food, such as leaves or wood. It is rather remarkable that they manage to extract nutrients out of them, especially the ones that feed on wood. Most of what they eat goes through their digestive system and comes out of the other end with little modification. A partially rotten log may contain long tunnels filled with what looks like sawdust. They are the holes made by beetle larvae as they grow and advance in search of more food. The sawdust is their poop, which takes the name of frass. Some caterpillars live inside a bunch of leaves which they tie together and curl up so they can hide from predators while they munch away. If you open one of these bundles you find a large amount of frass surrounding the caterpillar.

Caterpillar and some of its refuse or frass

© Beatriz Moisset

Larval tunnels on wood (possibly a beetle)

filled with frass

© Beatriz Moisset

At the other end of the spectrum, there are larvae whose mothers have provided with a rich, highly nutritious food. Many wasps and bees do that. In the case of wasps, the food is insects or spiders; bees, on the other hand, collect pollen and nectar for their brood. These larvae live in splendid isolation inside small compartments, called cells, built by their mothers. The amount of food supplied is slightly larger than the future adult bee or wasp. Almost all of it is converted into flesh and nothing is wasted. At the end of the larval stage, only a small pellet of fecal matter is produced. It gets the name of meconium, comparable to the first bowel movement of a newborn baby. The baby's meconium is the accumulated waste of a few months; so the similarity is strong.

Cell of Crabronid wasp larva (Trypoxylon collinum)

Opened cell reveals the fully grown larva and the pellet of meconium (left)

No remains of the spiders that fed this larva

© Beatriz Moisset

A lot more can be said about larval poop. A number of larvae use their own fecal matter to keep enemies away. Some carry their own feces as an umbrella, others build a little case. They hide inside it the way a snail hides inside its shell. Some insect larvae don't use real poop, but it looks like it. A whole group of caterpillars is called bird-dropping caterpillars. Still others fling their waste as far away as possible so as not to give away their position to possible enemies. I don't need to repeat these stories as I have written about them in two articles that you may find interesting: "The Poop Bug and the Golden Beetle," 2009 and "Poop Flinging and Other Poop Strategies," 2012.

Golden tortoise beetle larva carrying its feces

© Beatriz Moisset

Neochlamisus beetle larva and its fecal case

© Beatriz Moisset

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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2017

Milkweed's last hooray. Part two

Polished lady beetle (Cycloneda munda) on dying milkweed leaf

The milkweed food chain would be incomplete without predators and parasitoids. Most of them are out of sight in November; but a few are around feeding on whatever is available, mostly aphids.

Multicolored Asian lady beetle (Harmonia axyridis) pupa

Two species of ladybugs or lady beetles find abundant food on the dying milkweeds. A shiny adult polished lady beetle (Cycloneda munda) may be getting ready to hibernate. A little farther a pupa of the multicolored Asian lady beetle (Harmonia axyridis) stays still on a leaf. It is rather infrequent to find one so exposed. This one is darker than most pupae of this species, but as its name indicates, color variations abound. In another month it would become an adult, out of its pupa. It would turn out darker than most of its kind.

Multicolored Asian lady beetle adult

 Another type of aphid eater is present in numbers and feeds on the two species of aphids mentioned in the previous post. The larvae of syrphid flies are blind and worm-like, lacking legs. Despite these disadvantages, they have no trouble finding aphids to feed upon, provided that the mother was careful enough to lay her eggs near a growing and prosperous colony of aphids.

Syrphid larva (Eupeodes americanus)

Syrphid larva (Eupeodes americanus)

It is impressive to see these maggots thrashing around until they find a plump juicy aphid. They hold it with their strong mouth parts and proceed to suck all the internal fluids until the prey is reduced to a deflated piece of skin. You can see the front end of the larva acting as a pump, expanding and contracting. Oddly, the other aphids in the colony have no fear, no premonition of what is in store for them. I have seen them approaching and then walking all over a syrphid maggot in total indifference.

 

 

Syrphid larva (Eupeodes americanus)

 

In a couple of weeks this will be all over. No more active life in the milkweed patch; just a few flying seeds carried by their fluff. The monarchs are long gone. All others remain in the area in hidden places safe from the weather and from the occasional winter predator. They will all return to their usual activities next year, when the milkweeds start sprouting new shoots and providing nourishment to them.

Milkweed's last hooray
List of articles

© Beatriz Moisset. 2012 

Don't Kill Your Friends

Larva of Coleomegilla maculata, pink spotted lady beetle © Beatriz Moisset

Please, don't go about killing any bug in sight. Some of the ugly ones are your best friends. Take the little "alligator" shown here. If you look closely you will notice that it is devouring aphids.

Same as above, notice the aphids being eaten © Beatriz Moisset

 
The aphids escape notice at first sight. They are the ones that are sapping the juices from your plants and this little guy is going around vacuuming them as fast as it can.

Adult Coleomegilla maculata on spring beauty © Beatriz Moisset

And here is the kicker, that ugly bug will turn into a ladybug when it is fully grown.And remember that it probably eats more aphids at this stage than when it is fully grown. So, if you think about it, maybe it isn't ugly after all. It is beginning to look rather pretty, don't you think?

Polished lady beetle © Beatriz Moisset

List of Articles

© Beatriz Moisset. 2012

Poop Flinging and Other Poop Strategies

Caterpillar shelter

Many insects eat rather non nutritious plant parts. So they need to consume large amounts, extract the nourishment, such as proteins, and discard the rest at the other end. In simpler words: they eat a lot and poop a lot, or if you prefer, they produce large amounts of frass or waste material.
Wasps are some of the worst enemies of caterpillars. They are constantly seeking them to feed their young. Many wasps are superb at controlling insect pests. I would think twice before hurting one of them; they are our friends. Without them, there would be population explosions of plant-eating caterpillars.

Leaf-roller caterpillar and its frass

Caterpillars have devised different ways to hide and keep these ferocious predators from finding them. The so-called leaf-rollers fold a leaf, stitch it together with their silk and stay inside the little tunnel munching away in relative safety. The amount of frass that accumulates inside these little shelters can be impressive. One wonders how they can live in such conditions. Not pretty!

Tiny black dots of frass hurled by caterpillar

Unfortunately for the caterpillar, the smell of their poop is an excellent clue to their presence. You may say that predatory and parasitic wasps have a nose for food-related aromas. So, certain caterpillars have developed a singular strategy. They throw their waste material as far as they can; which can be pretty far. Eight to twelve inches for a caterpillar not much bigger than a grain of rice! That is as if you could throw the you-know-what several yards away.

The curious thing is that many moths and butterflies belonging to different families have come up with the same poop-flinging solution to hide from predators. Among them there is a skipper that you may probably have seen visiting flowers, the silver spotted skipper. It gets its name from the brilliant spot on its hind wings. When this skipper was a caterpillar it regularly shot cannon balls of its own frass as far as a couple of yards away. How about that!

Silver-spotted skipper

Bird-dropping caterpillar

(by Malcom NQ, Flickr)

Another poop strategy of sorts is that used by many caterpillars called bird-dropping caterpillars. Their appearance, as the name tells you, resembles a bird dropping. Apparently the ruse is convincing enough to discourage would be predators. No real poop is involved here, but it is worth mentioning in an article about poop strategies.

Leaf beetle larva hiding under its poop

And then, there are other insects, particularly a group of leaf beetles that have turned things around completely. Instead of leaving their poop behind, they proudly carry it around as a shield. Some build a sort of basket or nest above and around them. Others have a projection shaped like a coat rack, from which they hang their byproducts, castoff skin and poop. You can read more about one of them in The Poop Bug and the Golden Beetle

More on frass strategies

Silver-spotted skipper caterpillars and Adelie penguins both can fling poo to startling lengths

How caterpillars use their feces to fool corn

 
List of articles 

© Beatriz Moisset. 2012