What To Do When You Can’t Run

WHAT TO DO WHEN YOU CAN’T RUN 

August/September issue, 2007

Yes, there is such a thing as a hummingbird moth, and yes, you likely saw one in your garden. They seem to be everywhere this year.

It is easy to understand why this large “sphinx” or “hawk” moth could be mistaken for a hummingbird. They are certainly the size of one, have a rapid wingbeat, have a colouration that would suggest a hummingbird, and also has tufts of hair on the end of its abdomen that look a lot like feathers. And it loves flowers.

In fact, in the greater scheme of things, Nature may have intended it to be this way. Certainly if you look more like a hummingbird, than you do a moth, and are more inclined to feed during the day when most moths tend to be inactive, the chances of survival in a world full of predators seeking out evening moths, would appear to be greater.

If the hummingbird moth is quite large, then we can safely assume that the caterpillar is also. The caterpillar is among one of many hornworms, so-named from the hook or hornlike appendage protruding upward near the posterior end of the caterpillar. Although this horn appears dangerous, it is, in fact, quite harmless. Doubtless you have seen one of these caterpillars, at least, on tomato plants as they gorged themselves on the leaves of the plant.

Unlike the hummingbird that feeds, not by actually sucking nectar from the flower as many of us believe, but by inserting its long bill into the flower and lapping the nectar with its tongue, the hummingbird moth feeds as one might expect. It inserts a long, thin, needle-like mouthpart called a proboscis. When not in service this instrument stays coiled up like a garden hose, but when it hovers near a flower, the proboscis uncoils, much like a party noisemaker and dips deep into the flower.

So, if the hummingbird moth is indeed programmed to resemble a hummingbird to avoid detection, then it is definitely not alone. Insects, over many millennia, have evolved clever ways to avoid detection. These fakes and frauds use every scheme in the book. Some insects, when at rest, resemble dead leaves, others are transparent so their background shows through. There is a moth that mimics the leg movements and threat postures of a spider, and a spider that mimics both the appearance, movements and colour of a stinging, distasteful ant.

Others we are more familiar with, such as the Monarch butterfly and the viceroy butterfly. The perfectly edible, and likely quite delicious viceroy butterfly resembles the distasteful Monarch so expertly, that most birds and other predators avoid the viceroy as well. This characteristic of palatable butterflies mimicking unpalatable species can be found in other parts of the world too.

Patterns and structures on butterfly and moth wings may resemble many things. Some scientists believe that the distinct patterns on the edge of butterfly wings resemble caterpillars, giving the butterfly a better chance of breaking away. Hairstreak butterflies have false antennae and spots on the rear of their wings. Birds attack the wrong end in an attempt to grab the head, and the butterfly makes good its escape.

Another example of mimicry can be found among other species. Tiger moths, for the most part, are distasteful and primarily hunted by bats which use echolocation, or sonar, to locate their prey. Tiger moths are able to emit a supersonic sound of their own which warns the bats, who have acquired the experience, that this sound is coming from a potentially unsavoury meal, and avoid being eaten. The stonefly is an example of an insect that has developed a different approach. Their larvae, which live in streams, start feeding and growing in another month or two, and when the snow is on the ground, the adults emerge from the water and mate on the shore and the female lays her eggs back in the water. Sometimes you can see them flying around on winter days like so many oversized mosquitoes, but more often are found crawling over rocks and snow at stream edges where the adults feed on algae. What advantage does this backward life history serve? Well, fewer insect predators about in winter, better survival rate.

Perhaps the most unusual is the bird dropping moth which mimics, surprisingly enough, bird turds. I have watched these moths in absolute fascination as they deliberately perch on the edge of an object, and the more relaxed they become, the more they resemble a bird dropping, right down to the white, shiny splatter and greenish edging. There is a rule in Nature that you don’t mess with feces, because they can carry parasites and microbial diseases. Disturb it and the moth suddenly resumes the appearance of any normal looking moth.

My first encounter with this insect, to even know there was such a thing, was at Sandbanks Provincial Park. I was the Park Naturalist there, but it took a student staff member, known among her colleagues as “Buggy,” to reveal the fascinating story of this insect to me. I found it that morning on the doorknob to the Visitor Centre. So perfect was its camouflage as it dribbled down the side of the door knob, that I purposely avoided it, as I assumed it was the real thing, and gingerly opened the door by the stem of the knob. I knew the students would enter the building moments later by the same door, and saw no reason to stray from my reputation among the student staff as a jokester for which I had become infamous.

Imagine my surprise when one of the students excitedly displayed the moth on her finger as she came into work. Thus began my research into bird dropping moths, learning there were actually several species in our area. Today, I take more detailed looks at bird dirt, and have subsequently found may “droppings” that flew away upon being touched.

Walking sticks that resemble twigs, bitterns that blend in with cattails and actually sway to and fro with the breeze, insets that resemble the bizarre, and tree frogs that change colour to match their background. It’s a fascinating world out there as wildlife species play a game of “Catch me, if you can, but you have to see me first.”