Moths of the Limberlost: A Book About Limberlost Cabin

by Gene Stratton-Porter

In June of 1911, close six o'clock in the evening, I sat on the front veranda of the Cabin, in company with my family, and watched three moths sail past us and around the corner, before I remembered that on the screen of the music-room window to the east there was a solitary female Promethea moth, that day emerged from a cocoon sent me by Professor Rowley. I hurried to the room and found five male moths fluttering before the screen or clinging to the wild grape and sweet brier vines covering it. I opened the adjoining window and picked up three of the handsomest with my fingers, placing them inside the screen. Then I returned to the veranda.

Moths kept coming. We began studying the conditions. The female had emerged in the diningroom on the west side of the cabin. On account of the intense heat of the afternoon sun, that side of the building had been tightly closed all day. At four o'clock the moth was placed on the east window, because it was sheltered with vines. How soon the first male found her, I do not know. There was quite a stiff evening breeze blowing from the west, so that any odour from her would have been carried on east. We sat there and watched and counted six more moths, every one of which came down wind from the west, flying high, above the treetops in fact, and from the direction of a little tree-filled plot called Studabaker's woods. Some of them we could distinguish almost a block away coming straight toward the Cabin, and sailing around the eastern corner with the precision of hounds on a hot trail. How they knew, the Almighty knows; I do not pretend to; but that there was odour distilled by that one female, practically imperceptible to us (she merely smelled like a moth), yet of such strength as to penetrate screen, vines, and roses and reach her kind a block away, against considerable breeze, I never shall believe.

The fact is, that moths smell like other moths of the same species, and within a reasonable radius they undoubtedly attract each other. In the same manner birds carry a birdlike odour, and snakes, frogs, fish, bees, and all animals have a scent peculiar to themselves. No dog mistakes the odour of a cat for that of another dog. A cow does not follow the scent of horses to find other cattle. No moth hunts a dragon-fly, a butterfly, or in my experience, even a moth of another species in its search for a mate. How male moths work the miracles I have seen them accomplish in locating females, I cannot explain. As the result of acts we see them perform, we credit some forms of life with much keener scent than others, and many with having the power more highly developed than people. The only standard by which we can determine the effect that the odour of one insect, bird, or animal has upon another is by the effect it has upon us. That a male moth can smell a female a block away, against the wind, when I can detect only a faint musky odour within a foot of her, I do not credit.

Primarily the business of moths is to meet, mate, and deposit eggs that will produce more moths. This is all of life with those that do not take food. That they add the completing touch and most beautiful form of life to a few exquisite May and June nights is their extra good fortune, not any part of the affair of living. With moths that feed and live after reproduction, mating and egg placing comes first. In all cases the rule is much, the same. The moths emerge, dry their wings, and reach full development the first day. In freedom, the females being weighted with eggs seldom attempt to fly. They remain where they are, thrust out the egg placer from the last ring of the abdomen and wait. By ten o'clock the males, in such numbers as to amaze a watcher, find them and remain until almost morning. Broad antennae, slenderer abdomen, and the claspers used in holding the female in mating, smaller wings and more brilliant markings are the signs by which the male can be told in most cases. In several of the Attacine group, notably Promethea, the male and female differ widely in markings and colour. Among the other non-feeders the difference is slight. The male Regalis has the longest, most gracefully curved abdomen and the most prominent claspers of any moth I ever examined; but the antennae are so delicate and closely pressed against the face most of the time as to be concealed until especially examined. I have noticed that among the moths bearing large, outstanding antennae, the claspers are less prominent than with those having small, inconspicuous head parts. A fine pair of antennae, carried forward as by a big, fully developed Cecropia, are as ornamental to the moth as splendidly branching antlers are to the head of a deer.

The female now begins egg placing. This requires time, as one of these big night moths deposits from three hundred and fifty to over six hundred eggs. These lie in embryonic state in the abdomen of the female. At her maturity they ripen rapidly. When they are ready to deposit, she is forced to place them whether she has mated or not. In case a mate has found her, a small pouch near the end of her abdomen is filled with a fluid that touches each egg in passing and renders it fertile. The eggs differ with species and are placed according to family characteristics. They may be pure white, pearl-coloured, grey, greenish, or yellow. There are round, flat, and oblong eggs. These are placed differently in freedom and captivity. A moth in a natural location glues her eggs, often one at a time, on the under or upper side of leaves. Sometimes she dots several in a row, or again makes a number of rows, like a little beaded mat. One authority I have consulted states that "The eggs are always laid by the female in a state of freedom upon the food-plant which is most congenial to the larvae." This has not 'always' been the case in my experience. I have found eggs on stone walls, boards, fences, outbuildings, and on the bark of dead trees and stumps as well as living, even on the ground. This also, has been the case with the women who wrote "Caterpillars and their Moths", the most invaluable work on the subject ever compiled.

A captive moth feels and resents her limitations. I cannot force one to mate even in a large box. I must free her in the conservatory, in a room, or put her on an outside window br door screen. Under these conditions one will place her eggs more nearly as in freedom; but this makes them difficult to find and preserve. Placed in a box and forced by nature to deposit her eggs, as a rule, she will remain in one spot and heap them up until she is forced to move to make room for more. One big female Regalis of the last chapter of this book placed them a thimbleful at a time; but the little caterpillars came rolling out in all directions when due. In my experience, they finish in four or five nights, although I have read of moths having lived and placed eggs for ten, some species being said to have deposited over a thousand. Seven days is usually the limit of life for these big night moths with me; they merely grow inactive and sluggish until the very last, when almost invariably they are seized with a muscular attack, in which they beat themselves to rags and fringes, as if resisting the overcoming lethargy. It is because of this that I have been forced to resort to the gasoline bottle a few times when I found it impossible to paint from the living moth; but I do not put one to sleep unless I am compelled.

I never have been able to induce a female to mate after confinement had driven her to begin depositing her eggs, not even under the most favourable conditions I could offer, although others record that they have been so fortunate. Repeatedly I have experimented with males and females of different species, but with no success. I have not seem a polygamous moth; but have read of experiences with them.

Sometimes the eggs have a smooth surface, again they may be ridged or like hammered brass or silver. The shells are very thin and break easily. At one side a place can be detected where the fertilizing fluid enters. The coming caterpillar begins to develop at once and emerges in from six to thirty days, with the exception of a few eggs placed in the fall that produce during the following spring. The length of the egg period differs with species and somewhat with the same moths, according to suitable or unfavourable placing, and climatic conditions. Do not accept the experience of any one if you have eggs you very much desire to be productive of the caterpillars of rare moths; after six days take a peep every day if you would be on the safe side. With many species the shells are transparent, and for the last few days before emergence the growth of the little caterpillars can be watched through them.

When matured they break or eat a hole in their shells and emerge, seeming much too large for the space they occupied. Family characteristics show at once. Many of them immediately turn and eat their shells as if starving; others are more deliberate. Some grace around for a time as if exercising and then return and eat their shells; others walk briskly away and do not dine on shell for the first meal. Usually all of them rest close twenty-four hours before beginning on leaves. Once they commence feeding in favourable conditions they eat enormously and grow so rapidly they soon become too large for their skins to hold them another instant; so they pause and stop eating for a day or two while new skin forms. Then the old is discarded and eaten for a first meal, with the exception of the face covering. At the same time the outer skin is cast the intestinal lining is thrown off, and practically a new caterpillar, often bearing different markings, begins to feed again.

These moults occur from four to six times in the development of the caterpillar; at each it emerges larger, brighter, often with other changes of colour, and eats more voraciously as it grows. With me, in handling caterpillars about which I am anxious, their moulting time is critical. I lost many until I learned to clean their boxes thoroughly the instant they stopped eating and leave them alone until they exhibited hunger signs again. They eat greedily of the leaves preferred by each species, doing best when the foliage is washed and drops of water left for them to drink as they would find dew and rain out of doors. Professor Thomson, of the chair of Natural History of the University of Aberdeen, makes this statement in his "Biology of the Seasons", "Another feature in the life of caterpillars is their enormous appetite. Some of them seem never to stop eating, and a species of Polyphemus is said to eat eighty-six thousand times its own weight in a day." I notice Doctor Thomson does not say that he knows this, but uses the convenient phrase, "it is said." This is an utter impossibility. The skin of no living creature will contain eighty-six thousand times its own weight in a day. I have raised enough caterpillars to know that if one ate three times its own weight in a day it would have performed a skin-stretching feat. Long after writing this, but before the manuscript left my hands, I found that the origin of this statement lies in a table compiled by Trouvelot, in which he estimates that a Polyphemus caterpillar ten days old weighs one half grain, or ten times its original weight; at twenty days three grains, or sixty times its first weight; and so on until at fifty-six days it weighs two hundred and seven grains, or four thousand one hundred and forty times its first weight. To this he adds one half ounce of water and concludes: "So the food taken by a single silkworm in fifty-six days equals in weight eighty-six thousand times the primitive weight of the worm." This is a far cry from eating eighty-six thousand times its own weight in a day and upholds in part my contention in the first chapter, that people attempting to write upon these subjects "are not always rightly informed."