Black swallowtail caterpillars have good taste.  

Call them culinarily-inclined critters, but don’t call them late for dinner or underestimate their hunger. Swallowtails eat well and eat a lot, more than two times their body weight per day. All of these meals allow them to grow and grow — through five instars or development stages — before they metamorphose into a chrysalis. 

Before the eat-fest, caterpillars started their lives as eggs. These are laid singly by Mom, and one adult black swallowtail butterfly can deposit thirty to fifty eggs a day and up to 430 eggs in her lifetime. Caterpillars develop inside and will eat their way out of the egg and devour the shell as its first feast. 

Most caterpillars are specific in terms of their eating habits. In fact, many caterpillars can only eat a few plants and are dependent on these for their survival. Think monarchs, which are a one-plant wonder, eating only milkweed. 

Black swallowtail caterpillars have a hankering for herbs, being partial to parsley, dill, caraway, carrots and, one of my favorites, fennel. Besides these garden plants, swallowtail caterpillars will also dine on native and introduced plants such as Queen Anne’s lace, rue, wild parsnip and even poison hemlock, among others greens. Hemlock, while known to be poisonous to some, won’t affect swallowtails, which can detoxify its poison. 

It is not just an all you can eat buffet for the swallowtail caterpillar. Between and during feedings, swallowtails must avoid predators.  To do this, these caterpillars use cryptic coloring that makes them appear as bird droppings. Thus, to say they look like crap would not be inaccurate or insulting. It is simply a survival mechanism.   

Another tactic is to use their osmeterium — a bright orange, forked appendage that comes out of the caterpillar’s head — for protection. This biological weapon has a stinky chemical repellant that no foe wants to be at the business end of. 

Swallowtail caterpillars are now making their last stand. Soon that delicious greenery will wither and die as most plants senesce for the season, leaving the hungry caterpillar to go into its winter survival state. That would be a chrysalis. This structure is held fast to a plant by a silken thread hammock at the top and a Velcro-like stem called a cremaster to anchor the hind end of the chrysalis to a twig, stem, or other plant part. 

In our region, swallowtail caterpillars have two generations, while southern populations can have three in a season. The first-generation chrysalis will hatch in eighteen days but the last one will overwinter. Another good reason not to clean up your yard and garden, these and many other insects are amongst the leaves and debris that some folks consider messy. 

A large and beautiful black swallowtail butterfly will emerge from the overwintered chrysalis in spring. These butterflies are protandrous, meaning the male emerges before the female. Female fertility improves with weight so it is to their advantage to stay as long as possible as a caterpillar and eat as much as possible to try to put on weight for their reproductive success after they emerge. Males are smaller than females, though their colors are brighter and bolder. Females also have more blue in their wings than males. 

After emerging next spring, these long-tailed lepidoptera will be ready to mate and bring forth the next generation by laying those eggs.  And on and on it will go from there, which seems a good life: eat delicious food, resist predators, sleep for a while and then start again.

Suzan Bellincampi is Islands director for Felix Neck Wildlife Sanctuary in Edgartown and the Nantucket Wildlife Sanctuaries. She is also the author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.