Friday, July 16, 2010

The Very Hungry Caterpillar

As it is currently the Year of the Tiger, I would love to be able to say that this big, fat caterpillar I found in my garden is the larva of a western tiger swallowtail, one of the few species of butterfly that flit through our neighborhood. But I'm afraid that would be a lie. A tiger swallowtail caterpillar is club-shaped and has eerie eyespots on its back that make it look like a creepy little snake lurking in the leaves, a perfect disguise for scaring off a hungry bird.

(Or a prying kid. I can still remember clambering through shrubs in our Long Island backyard as a kid and suddenly coming face to face with a hideous lime-green Something with enormous yellow-and-black eyes bulging from its head. I screamed and ran. Two decades passed before I figured out it was nothing but the caterpillar of a spicebush swallowtail butterfly.)

No, the sad truth is, I have no idea what this caterpillar is. I thought at first it was the young'un of the cabbage butterfly (also called the cabbage moth, even though it isn't one; in that sort of mood, you might as well call it the cabbage frog, or the cabbage gnu, since it isn't a frog or gnu, either). But that plump larva apparently has yellow stripes, not white.

Not that many of our cabbage-butterfly larvae (known as cabbage loopers) ever survive to become yellow-striped green teenagers. Last year, we planted lots of broccoli, collards, and kale in our garden, so our little vegetable patch promptly became a mecca for fluttering crowds of cabbage whites ready to lay eggs on suitable host plants for their young. When I discovered hordes of little green caterpillars inching and munching their way through the crop, I looked for good ways to dispatch them--and there are many--before settling on a most excellent one: hire your money-hungry kid to find and collect them at a bounty of 10 cents per larva.

Our resident bounty-hunter amassed a fortune in this enterprise and even enlisted her cousin for an afternoon. The caterpillars went on to become snacks for a friend's chickens.

This one, however, wasn't gobbling up our crops. It clung to the stem of a perennial in a planter, a tall purple-flowered spike known as veronica or speedwell. (I fully intend to name a character Veronica Speedwell in that novel I fully intend to write one day.) So it was left unscathed.

We're guessing it might be the larva of a yellow Clouded Sulphur butterfly. But there are an awful lot of caterpillars that meet the description of "green with white stripes." If I had a dime for every species whose larva fit the bill, I'd be almost as rich as my daughter.

Thursday, July 1, 2010

Dragons in the Garden, Part II

This dragon-like little creature lurks in a shrub outside my front door. I've seen others of its kind skulking in the garden, and have witnessed adult humans yelping and shrinking away from them. But these insects are not only completely harmless to people and plants, they are also a gardener's best friends.

Because these menacing mini predators are none other than the babies of that scourge of aphids, a ladybug.

In this insect family, it's the adults who are endowed with all the features that make people say, "Awww." They're pudgy. They're round. They come in Gummi-bear colors. They often have polka-dots. They trustingly walk on your arm. Sometimes they forget to completely fold their wings underneath their wing cases and potter around looking like church ladies with too-long petticoats or little boys who've forgotten to tuck in their shirt tails. What could be more charming?

(OK, they also ooze foul-smelling yellow fluid from their joints if alarmed. Nobody's perfect.)

The larvae, however, won't be winning any Beautiful Baby contests anytime soon. Upon hatching, they look a bit like deer ticks (minus one pair of legs). They grow into elongated little black alligators, eventually acquiring bright orange, red, or yellow markings. (Thus far I haven't been able to determine whether lady-beetle larvae are as foul-tasting to birds as the adults are and if these colors serve as fair warning to them.)

Mama lady beetle considerately lays her eggs on a leaf in a veritable smorgasbord of aphids, so when the larvae hatch, they blunder into a feast. I imagine that'd be like waking up in the morning surrounded by chocolate croissants. The babies tuck into the meal about an hour or two after hatching, stabbing aphids right and left with hollow mandibles and slurping them up like milkshakes.

Then they probably enjoy a nice aphid-dinner mint.

A typical larva with a good appetite may gobble up 30 to 40 aphids a day over the course of four or five weeks. (According to many sources, "the convergent lady beetle may eat its weight in aphids every day as a larva." This sounds like an awesome statistic until you realize that you don't know how much a lady-beetle larva or an aphid weighs. Still, that's a lot of chocolate croissants.)

But wait, kids! It's WORD PROBLEM TIME! According to a 2007 scientific paper, "Molecular sabotage of plant defense by aphid saliva," a typical adult aphid weighs approximately 1 milligram. If an aphid weighs 1 mg, and a lady-beetle larva stuffs itself with 40 aphids, how much does the larva weigh?

Adult lady beetles consume a lot of aphids too, but they're not as voracious as the growing youngsters, plus they can fly away if your garden runs out of aphids and other small chitin-clad snacks. The larvae can't.

I once watched a lady-beetle larva approach a cluster of fat aphids on a stem--so delighted with its find that it was nearly rubbing its hands (if it'd had hands) together with anticipation like a cartoon fox in a henhouse--only to be met by a hostile ant that was guarding the aphids; ants tend to little herds of aphids so as to enjoy the honeydew they produce. The ant was ferocious; the larva seemed surprised; the aphids were oblivious. The ant won the gladiatoral event, but sort of by default--the larva did what looked like a pratfall, falling off the stem in astonishment, actually a very effective "I'm outta here" reflexive response. This time the ant was the one to dust off its virtual hands, satisfied with a job well done.