You may be asking yourselves: what is it with the weird title of this article?
Not only is it to catch your attention, but it also notes the difference between this and two of our previous articles in the Millstone News; one dealt with fuzzy caterpillars and the other with eastern and forest tent caterpillars, all caterpillars that use their hairiness for defence against predators. In this article we look at a few examples of butterfly and moth ‘cats’ whose body surface is not covered by hairs or tufts.
The life cycle of butterflies and moths consists of egg, larvae (caterpillar), pupa, and adult. The adults mate and lay their eggs on or near host plants and the caterpillar that emerges from the egg is essentially an eating machine. It feeds on host plants to grow in size and build up sufficient reserves to last through the pupa stage and into adulthood. Caterpillars are composed of a head with strong eating mouth parts and two simple eyes, three thoracic segments each with a pair of legs, and ten abdominal segments typically with five pairs of false legs, termed prolegs, to allow the caterpillar to move to new sources of food. Caterpillars are vulnerable to predation while feeding and have evolved various physical and behavioural adaptations to help protect the larvae from birds, insects, spiders and other predators. As you can see in the following picture these adaptations are not always effective.
Our survey of hairless caterpillars starts with one of the most widely recognized butterfly larvae. Your best chances of seeing a monarch butterfly caterpillar is by checking out the young leaves of milkweed plants on which this caterpillar feeds. It incorporates into its tissues cardiac glycosides found in the milkweed’s white sap that are distasteful to would-be bird predators. Accordingly, while this caterpillar has two sinister looking fleshy filaments at its front end and two shorter ones at its back end, it does not need these or a hairy covering for protection. The bright green, yellow, and black striped caterpillars can grow to six centimetres in length before pupating. We were pleased to note the increased numbers of milkweed plants, many of which hosted a monarch butterfly caterpillar, near the cottage this summer.
The snowberry clearwing moth caterpillar has a distinctive fleshy horn at the back end of its 4.5 centimetre body. They feed on honeysuckle and snowberry. In addition to their seemingly menacing horn, they thrash violently from side to side when disturbed and may also regurgitate a sticky green fluid to evade predators.
Another horn-bearing caterpillar is the gallium sphinx moth. These caterpillars are highly variable in body colour, ranging from green to brown or black. Along with their menacing red or black fleshy horn at their backend, they also possess distinctive sub-dorsal spots along both sides of their bodies. They can grow to seven centimetres in length, preferring to feed on members of the family of evening primrose plants.
The colouration of the spiny oak slug moth caterpillar is highly variable. One distinctive feature of this two-centimetre-long caterpillar is the front end which possesses three pairs of elongated lobes and the backend which has two pairs of elongated lobes that bear numerous stinging spines for protection. These secretive caterpillars can be difficult to locate as they usually hide between leaves during daylight. They feed on the leaves of a range of woody plants. This one was feeding on basswood leaves.
The European corn borer is an introduced species that is a member of the large family of pyralid moths. The caterpillar bores into the ear of corn and feeds on the cob, out of sight of many predators. It is an important pest. We were not happy to discover this one when we husked the corn for our cottage corn roast.
The red-humped oakworm caterpillar is a member of the family of prominent moths. Some members of this family are capable of shooting acid from a neck gland and others regurgitate fluids to deter predators. This caterpillar can grow to two centimetres feeding on beech, chestnut and oak leaves. It is most often observed in the fall which is when this individual was photographed.
The brown hooded owlet moth caterpillar has stunning markings in shades of yellow, black, red, and white, presumably to ward off would-be predators. They feed primarily on the flowers of asters and goldenrod, growing to 4.5 centimeters in length. This caterpillar is often attacked by flies who lay their oval white eggs on the caterpillar. When the egg hatches the fly larvae burrows into the caterpillar where it consumes the host.
Should readers be interested in additional information on caterpillars you could consider David L. Wagner’s Caterpillars of Eastern North America, and Amy Barlett Wright’s Peterson First Guides – Caterpillars.