In Part I of this article, I discussed how we can use simple pitfall traps to capture nutritious foods for pet reptiles, amphibians and invertebrates. While writing, it occurred to me that one of North America’s largest and most interesting beetles, the caterpillar hunter (Calosoma scrutator), often turns up in such traps.
Interesting but Ignored
Caterpillar hunters exhibit many qualities that render them ideal terrarium subjects. They are large, bold, diurnal, brightly-colored, voracious predators, temperature-hardy and breed well. Despite this, like most US natives, they receive virtually no attention from hobbyists. Caterpillar hunters are, however, much in demand elsewhere – on my last visit to Japan, entomologists at the Tama Zoo (which hosts a huge building and an outdoor exhibit for insects) assured me they would accept all that came their way.
Our native caterpillar hunters are mostly large and brightly-colored, and spend the day searching for insects and their pupae. Over 2,000 species (Family Carabidae) roam our forests, fields and parks, with 40,000+ having been described worldwide. One, the forest caterpillar hunter, was imported to the USA from Europe in 1905 to battle gypsy moths. The grub-like larvae of most are also predacious, constructing burrows from which they ambush passing insects.
Caterpillar hunters are the most numerous predators within many habitats. Calleida decora, for example, achieves densities of over 5,000 individuals per acre on US soybean farms. Much favored by farmers battling the velvet bean caterpillar, a single beetle may consume 7-10 caterpillars each day, and each female produces 800-1,000 eggs.
Caterpillar hunters make fascinating terrarium subjects. Clad in beautiful iridescent colors, most are not at all shy about revealing a range of interesting behaviors. They do well at normal room temperatures and can be housed in planted terrariums or simple plastic enclosures. Adults hibernate during the winter, with some species reaching at least 3 years of age.
I have bred two species in captivity, and it seems likely that many others would be equally cooperative. Caterpillar hunters can be fed crickets, newly molted (white) mealworms and their pupae, waxworms (which, being caterpillars, are a favorite!) and wild-caught insects.
As certain species defend themselves with irritating secretions, caterpillar hunters are best handled with gloves of tongs.
An interesting account of caterpillar hunter behavior is posted at
Caterpillar hunter image referenced from Wikipedia and originally posted by Fritz Geller-Grimm
Caterpillar hunter larva image referenced from Wikipedia and originally posted by Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org