by Roy Lukes

That Hummingbird May Really Be A Moth

This Pandora Sphinx moth caterpillar was eating its fill of wild grape leaves, very common plants in northeastern Wisconsin.

What a good month September is for studying caterpillars in spite of the fact that many people have little to no use for them. Much of their disdain for these fascinating creatures may have developed as a result of picking the huge green tomato hornworms off their garden tomato plants, or simply because the caterpillars they did encounter were either grotesque or ferocious in appearance, although totally harmless.

Actually a lot of caterpillars are considerably more interesting and easier to study and admire than the adult insects into which they will eventually develop. Elementary students may take on an entirely more sensitive outlook toward nature having watched some Monarch caterpillars eat their way to maturity on milkweed plants taken into the classroom, and finally witness the emerging of the adult butterfly being released outdoors so it can begin its migratory flight to Mexico.

Several nights ago Charlotte and I were thrilled at the sight of one of the sphinx or hawk moths hovering at our kitchen window, its small eyes clearly "glowing" red with eye-shine from the reflected lights within our house. It was a large moth having a wingspan of at least four inches, and my guess is that it was a Pandora Sphinx Moth (Eumorpha pandorus).

It was our friends Nick and Gail, sharp-eyed nature observers that they are, who alerted us recently to the incredibly handsome large Pandora Sphinx Moth caterpillar they discovered feasting on some grape leaves in their backyard. The three-inch-long larva was naturally very stationary while tightly clinging to the grapevine with its five pairs of so-called prolegs making the creature quite easy to photograph.

This larva is known to retract its first two body segments, the first being its head, into the third segment when disturbed which is exactly what this slow-moving but wary creature did. The three sets of tiny true legs, situated on the caterpillar’s first two segments, are then also pulled inward and hidden from view. It usually walks and feeds with the first two body segments and true legs fully extended.

Those of you who have removed tomato hornworms from your tomato plants know how firmly these caterpillars can cling to the vines. The larvae (LAR-vee), or caterpillars, of moths and butterflies generally do not have more than five pairs of prolegs, one pair being located on the sixth, seventh, eighth, ninth and last body segments. Each short wide proleg is provided with a number of very tiny hooks called crochets (cro-SHAYS) which enable the creature to quite tenaciously grip to whatever it is feasting upon.

The hawk moths are also referred to as sphinx moths from the appearance of the large green caterpillars of most species that have the ability of rearing up their front ends in mock defense when disturbed, thereby resembling the well-known "Sphinx."

Another distinctive feature of most larvae of this large group of moths is their "horn" or whip-like tail on their last segment. Even though they look quite ferocious they are in reality entirely harmless, at least to humans. The young caterpillars of the Panrodus Sphinx Moths also have the typical "horns" near their rear ends in their first two or three instars (total skin molts) but these eventually disappear before the caterpillars reach their greatest size and are ready to pupate. In place of the lost horn will be a shiny black bump outlined in white.

Larvae of Pandorus Sphinx Moths start out being green for the first several instars and then either remain green or gradually turn brown for the remainder of their larval stages or instars, usually five in number. The proboscis (pro-BOS-sis) or hollow tongue of this moth, like other hawk moths, is quite long. In fact it is the Clearwing Hummingbird Moth, hovering during broad daylight at people’s flowers, with its long outstretched tongue appearing for all the world like the straight beak of a hummingbird that has brought about its unusual name.

Most people, when reporting this very strange "hummingbird," tell of the little bird having two antennae-like projections coming from the front of its head. Indeed these are the antennae found on the heads of all moths and butterflies – but never on the heads of hummingbirds!

The caterpillars of the Pandorus Sphinx Moths, having finally eaten their fill of either the leaves of grapes or Virginia Creeper in this region, will crawl to the ground and slowly dig themselves several inches downward. The pupa will be large, somewhat tapered at each end and appear as though it has been varnished. Some of the pupae (PEW-pea) will have what appears to be a little turned-back "jug handle" in which will be formed and encased their long tongue. The adult hawk moths will emerge from their underground pupae next spring, crawl to the surface and fly into the night, one of the swiftest fliers of the entire large and fascinating moth family.

This column appeared in the Door County Advocate on 09/13/2002.
© Copyright 2002 Roy Lukes. All rights reserved.