The weight of a caterpillar can vary significantly depending on its species and stage of development. Generally, most caterpillars weigh anywhere from a few milligrams to several grams. For instance, a common monarch caterpillar may weigh around 0.5 grams when fully grown, while larger species like the tomato hornworm can weigh as much as 4 grams.
After hatching from an egg, caterpillars start very small, often less than a gram, and then gain weight rapidly as they eat and grow. They typically undergo several molts during their larval stage, shedding their skin and increasing in size—and weight—each time. Ultimately, the weight is an important factor for their survival, as it directly affects their ability to store energy and eventually pupate into a butterfly or moth.