(This column was first published in the October 2, 2000 Buffalo News.)
Each of us has a list of preferred foods. Some of us enjoy old fashioned meat and potato meals. Others like more exotic dishes -- Mexican, German, Indian, Polish or one of the many varieties of Oriental. Some of us are vegetarians. And of course nowadays too large a proportion of us practically exist on junk food.
But most of us eat a widely varied diet, enjoying on just one day foods from several of these and still other categories.
Not so, many insects. Their lives are tied very closely to a diet of specific foods. If the food is not available, the insect will not be found in that region. If the food is available nowhere, the insect does not have the ability to change its diet; it will almost certainly disappear.
One association with which many readers are already familiar is the monarch butterfly's with milkweed plants. The butterflies gain from their diet on these bitter plants some of their poisonous glycosides and these chemicals provide them with a defense against predators -- of course, only after the predator learns, having been sickened by its first meal. In fact another butterfly, not even from the same genus, the viceroy, is a near mimic of the monarch. Although some now question the theory, earlier entomologists have claimed that this is an example of a kind of convergent evolution called Batesian mimicry, the viceroy taking advantage of the monarch's evil taste to predators without having to eat those nasty milkweeds itself, simply by copying its coloration.
I was introduced a few days ago to another and I believe even tighter tie between plant and insect by Rob Eberly and Tim Seburn in Fort Erie, Ontario. (I was in Canada on a more serious mission, to gather information about the many dead salamanders, fish and birds along the Lake Erie shoreline. I hope to report on that in a future column.)
In any case, Rob guided me to Tim's home where he said that our host could show me a caterpillar called an orange dog. It is the larva of one of our most beautiful butterflies, the giant swallowtail.
This butterfly is indeed a giant, its six inch wingspan making it the largest butterfly in North America. Its base color is black and it sports bright yellow markings that, when seen from above, look like a U under a V on its back. I have never seen one. But that is not a serious mark against me; this species has never been reported on any of our Niagara County Fourth of July counts.
And indeed there were at least a half dozen orange dogs resting on a bush in the Seaborne yard. Talk about the ugly duckling metamorphosing into a swan: these had to be the ugliest caterpillars around. Their mainly brown and white markings made them look exactly like bird droppings. What an unusual way to avoid predation.
Why are they called orange dogs? Quite simply because this species lives exclusively on citrus trees. Of course, we don't have any orange or lemon or lime trees, but we do have two trees of this family in this region: the hop tree and the prickly ash.
And the tree on which we found these larvae. The bush was a hop tree. No nice citrus fruit unfortunately but oddly flattened circles of fruit that looked like inch diameter brown flying saucers.
So I found in that one yard two rare species new to me, an insect and a tree. I came away wondering if this pair marched together onto Noah's ark. -- Gerry Rising