I previously wrote about incomplete metamorphosis, where insect babies (nymphs) hatch from eggs more or less looking like adults. Complete metamorphosis is a totally different game–the babies (lavae) look absolutely nothing like the adult form, to the point where you may not even know that they are insects at all. Once you know what to look for, identifying larvae is much easier.
Questions to ask when you see something that might be a larva:
- Where do you see it? On a plant? On the ground? In the water?
- How is it shaped? Does it have a visible head? Does it have legs?
- If it does have legs: how many? What do they look like? Are there any other appendages, like jaws or prolegs?
Photo examples above:
Green lacewing larva. These larva are predatory and have large biting jaws. Some species also use camouflage, covering their bodies with debris which may include the emptied out husks of their prey. If you ever see a white fluffly blob meandering around on a tree, chances are you are seeing a green lacewing larva.
Mosquito larva (Asian tiger mosquito). Mosquitos spend the first part of their life in the water–females lay eggs on the surface of stagnant water, and after hatching the larvae wiggle around with their tails out of the water (they breathe through a tube at the end of their abdomen–you can see a little knob in the photo). It’s interesting to note that mosquitos are flies, yet I don’t think anybody would mistake a mosquito larva for a maggot. Even within insect orders there is substantial diversity.
Lady beetles. While the lady beetle family has a variety of species that look very different from one another, most people picture a black-spotted red beetle when they think of a ladybug/lady beetle. The larvae of these particular lady beetles also look fairly similar, and it can be hard to tell them apart unless you know what to look for. In general, they are black and orange, are textured and look “armored,” and have three sets of fairly long legs. You will often find them on plants that have aphid infestations, as the larvae are predatory on them.
Leaf beetles (blue dock beetle). Leaf beetles are another very large group with few similarities between species. You will typically find leaf beetle larvae (you’d never guess) on leaves of their host plants. These larvae can do a substantial amount of damage to crops if they go unchecked. Like lady beetle larvae, they have three sets of legs and a segmented, textured body. When I first saw these larvae, I was able to guess what species they were because this plant was infested with the adults (and they were the same color!)
Scarabs. Another beetle, but this one is much different. Scarabs are an enormous group of species, but their grubs generally look the same and develop concealed underground or in rotting wood. The grubs are soft and fleshy, with three sets of very long legs and a prominent head capsule. It is fairly rare to see one without busting up old logs or digging holes, but they do occasionally venture out in to the wide world. The adult shown here is a masked chafer, but I’m really not sure about the ID of the grub (they are hard to tell apart!)
Io moth. On to caterpillars! Most people are familiar with caterpillars (the larvae of butterflies and moths), and may even be able to identify (or at least recognize) a few. But caterpillars can be tricky as well, because they look so different from one another, and there are a few other types of insects with caterpillar-like larvae. Sawflies, for instance, can look almost identical to caterpillars, except they have a different number of prolegs. Prolegs are those little fleshy suction-cup things caterpillars have to keep them from falling of leaves they are feeding from and living on, but they are not true legs, and butterflies/moths rarely have more than 5 pairs of prolegs (inchworms and loopers have two or three sets!). Sawflies will have more than 7 prolegs. Some caterpillars protect themselves with venomous spines, like this io moth caterpillar. If you are able to get a side or bottom view of a caterpillar, you can see the number of prolegs to confirm that what you see is a caterpillar after all.
Tawny emperor. These caterpillars are interesting to me, because their head capsules are covered in little horns (I think it makes them look like Dutch rabbits!), but otherwise they look fairly standard for caterpillars. As with all larvae, you’d never guess what the adult looks like from seeing the babies.
Posted August 18, 2017