Wild Neighbors: Holes in the Lid

By Joe Eaton
Wednesday February 09, 2011 - 12:21:00 PM
The Ceanothus silk moth has a brief adult life.
Linda Tanner
The Ceanothus silk moth has a brief adult life.

Last week I foolishly offered to try to identify a moth. There are only 4500 named moth species in California. Piece of cake, right? 

I was expecting a photograph of the creature, but it arrived in a jar. It clearly wanted to get out. It was small and brown, with no vestige of a pattern. I opened Jerry Powell and Paul Opler’s magisterial Moths of Western North America to the color plates. There were only a few hundred species that matched it. At least it wasn’t a light brown apple moth: Wings were the wrong shape. It might well have been a member of the noctuid family, an extremely speciose group. Or it could just as easily have been a geometrid, or something else. Lacking a microscope and dissecting kit, there was only so far I could go with this one. 

I’ve never exactly been a moth person, but I can understand the attraction. We had serious moths in the South. Once a female luna got into our house in Little Rock, laid her eggs on the living room curtains, and expired. When I had to assemble an insect collection for high school biology, I tried the classic bait: a mixture of bourbon (Four Roses, for medicinal purposes only) and molasses smeared on the trunk of a longleaf pine. I can no longer recall what I caught, but there may have been underwings (Catocala). Powell and Opler write that sugaring for moths isn’t as effective in California, probably because our summer evenings aren’t humid enough. 

A few years ago, on a trip to Hawai’i, I heard about the semi-mythical green sphinx moth of Kau’ai and thought it would be great material for an article. (The moth has been found and lost and written off as extinct and found again over a couple of centuries; its larval food plant is unknown.) The piece eventually saw print in a national environmental magazine, but only after the life had been edited out of it. At one point in the sphinx saga, I wrote about a forestry worker who found a female in the act of laying eggs and enclosed her in a glass jar. My draft came back reading “a glass jar with holes in the lid.” I objected that the holes were conjectural and at this point impossible to verify. The editor’s response: “How would you feel if someone shut you up in a glass jar with no holes in the lid?” 

So I’ve left the moths alone for awhile. But I got interested in them again recently while working on a project about butterflies. There’s a tendency to see moths as the poor relations of butterflies: drab skulking nocturnal creatures. That’s hardly a fair generalization. 

Moths as a group are far more numerous and diverse, physically and ecologically, than butterflies. (It makes more sense to think of butterflies as a specialized lineage of moths rather than a separate category. Butterflies are to moths as snakes are to lizards.) 

It used to be safe to say that all butterflies were day-fliers and most moths were night-flyers. Then the taxonomists decided that one obscure tropical moth family, the Hedylidae, were genetically closer to the true butterflies and the skippers than to other moths. 

Although a few hedylids are active by day, most are nocturnal. 

The diurnal habit is not all that uncommon among moths, having been documented in at least sixteen families. 

The consensus now seems to be that butterflies differ from moths in having club-shaped (as opposed to feather- or comb-shaped) antennae and lacking the mechanism that allows moths to hook their wings together. Most other butterfly traits are shared by at least one family of moths. 

Moths and butterflies as a whole—the order Lepidoptera—are thought to share a common ancestor with caddisflies, small winged insects with aquatic larvae. The most primitive living moths have functional jaws as adults: some feed on pollen, others on leaves. One species, Epimartyria pardella, survives in coastal redwood forests. More typical moths, like butterflies, have a siphon-like proboscis that confines them to a liquid diet. Some, notably the giant silkmoths, have lost their mouthparts and never eat as adults. Uninterested in nectar, they’re ecologically irrelevant to flowering plants. All they do is mate and die. I would have felt better about that luna if I had known that. 

Ecologically speaking, there’s very little moths haven’t tried. Some Hawai’ian species have larvae that are ambush predators: they hold themselves at an angle from a tree branch, looking as much like a twig as possible, until a fly or other prey item comes within reach; then, blam! Adult moths of the Southeast Asian species Lobocraspis griseifusa will drink human tears. There are flightless moths, mostly on oceanic islands where not being blown out to sea has adaptive value, but at least one (Areniscythris brachypteris) in sand dunes on the central California coast. A. brachypteris has outsized hind legs that allow it to jump up to twenty times its body length: a moth converging on grasshopperhood. 

All of this was fascinating, but no help with the brown moth in the jar. I let it go its anonymous way.