A Woolly Flock
HARDLY a season passes without my being in receipt of one or more inquiries, personal or by letter, concerning this snowy brood which haunts the alders in the swamp or along the road-side, and which envelops the smaller branches in its dense, feathery fringe. It is often one of the most frequent and conspicuous incidents in a country walk during its season, and its season ranges from its height in early summer until the frost. And yet how few there are, even of those, perhaps, who pass it every day, who have any definite idea of its character!
I know one rustic who claimed that it was "dry-rot," or a "speeshy of mould"; but the woolly phenomenon is commonly dismissed by the rural mind with the observation that it is "bugs of some sort." In this case the haphazard verdict happens to be the literal truth, though the speaker little suspects how closely he has discriminated. But his present skill is easily accounted for when we remember that only yesterday he had a great deal to say about "June-bugs" and "lightning-bugs." He will tell you all about "lady-bugs," too, and "rose-bugs," and "horn-bugs," and "pinch-bugs"—and has he not often given his strong opinion on "potato-bugs"?—not one of which insects is in the least entitled to the name of "bug." Only this very morning he asked me if I was "as fond of goin' buggin' as I used to be." But to the granger laity the entomologist is always a "bug-hunter," even though no single species of a bug is to be found in his entire insect cabinet.
What, then, is a bug, and why is the discrimination of "bugs of some sort" so truly applicable to this brood with the snowy wool which grows upon the alder twigs?
The term "bug" has almost become a popular synonym for "insect." All bugs are insects, 'tis true, but it by no means follows that all insects are bugs. The "squash-bug" is almost the only insect that is known by its true title in the popular vocabulary, for this disgusting insect is in truth a typical bug.
But who would ever think of calling the whizzing harvest-fly a "bug?" Rather will they persist that he is a "locust," which he is not. He should be called the cicada. The "grasshopper" of the fields is the true locust, whose swarms of certain species in the Orient have so often shut out the sun, and whose voracious feeding has laid waste whole square miles of vegetation in a single night.
But such a swarm of locusts as we read of in Scripture, and frequently in the history of modern times and in our own country, would be comparatively tame and merely amusing affairs were they composed of our so-called "locust"—he of the whizzing timbrel in the sultry August noon. For this insect has no teeth, and could not bite a blade of grass if it wanted to. And herein we see one of the peculiarities which constitute him a "bug," and which also includes in the same company our woolly swarm upon the alder twigs. In place of teeth these insects are supplied with a beak for sucking the juices of plants. If we carefully examine the dense snowy mass we find it composed of small tufts closely crowded together, each tuft being borne upon the plump body of a small insect whose beak is deeply sunk into the tender bark.
I have separated one of the little creatures, and furnished his portrait as he appears when viewed through a magnifying-glass, only the lower portion of his body being covered with the wool, his head and legs being usually concealed beneath the pluming growth of his neighbors. This feathery growth seems of the most delicate consistency—in truth, more suggestive of white "mould" than any other natural substance, and seems to proceed from pores in the plump body beneath it. The slightest breath wafts the cobwebby tips of the fringe, and the least rude touch easily dislodges it, exposing the round, naked body of what is now clearly seen to be an aphis, or plant-louse, which nature, for some reason, has seen fit to clothe with swan's-down.
In early June the white down first appears on the alders in tiny patches here and there. This gradually extends down the stem, at length, perhaps, completely encircling it, and thus remaining for weeks, the full-grown aphis at last attaining a length of about three-sixteenths of an inch.
A similar brood is sometimes seen in profusion on beech-trees and also on the apple-tree. But if we imagine that because these insects are without teeth they are therefore harmless, we are greatly mistaken. What they lack in individual effect they fully compensate for in numbers, and the combined attack of a girdle of thousands of these sucking beaks, for weeks absorbing the sap, may often result in the death of the branch beyond them.
Dr. Harris, in his admirable work on "Insects Injurious to Vegetation," tells us that "in Gloucestershire, England, so many apple-trees were destroyed by these lice in the year 1810 that the making of cider had to be abandoned. So infested were many of the trees that they seemed, at a short distance, as if they had been white-washed."
Other insects, such as the flea and the mosquito, are also possessed of similar "beaks for sucking," but neither of these examples is a bug, both being flies—the flea merely a wingless fly with wonderfully developed legs. Our entomology tells us that a bug is a member of the Hemiptera, meaning "half-winged;" the wings of the typical bug, like the squash-bug, being transparent for only about half their length. But as in the flea among flies, here we find myriads of true bugs without a vestige of wings, and others, like the cicada, with ample wings as clear and free from opacity as those of a fly. It would take more space than I have at disposal to tell precisely what a bug really is entomologically, such a diversity of forms is presented in the family. But the sucking beak, and the fact that the average bug is born a bug from the egg, instead of going through the usual transformation of larva, chrysalis, and imago, will have to suffice us for the present. Here, for instance, is the great sub-tribe of the aphis, to which our woolly specimen belongs. What is their life history? The eggs of the mother aphis are laid in the autumn, giving birth to the baby swarm in the following spring. In an almost incredible time they have multiplied to such an extent that the twigs of our roses and many other plants are lost to view in the encircling swarm. The secret of this wonderful arithmetical progression may be seen in the following quotation, which applies to aphides in general:
"The plant-louse of the apple-tree produces one hundred young ones in a single generation, these being born alive, and each of these brings forth others in equal number, until, at the end of the tenth generation, which is reached before the coming of frost, the original aphis has become the mother of one quintillion of her species."
But up to this time nearly all the aphides have been females; in the last generation the winged males appear, and are seen assembled among the swarm—the last mother brood laying the eggs which are to start anew the cycle of life the following season.
So far as I have observed, however, the woolly species of aphis never acquires wings, nature having in a measure compensated for their absence in the growth of plumy down, which, according to Harris, is so buoyant as to enable the insect to be borne upon the breeze from tree to tree. To this resource he attributes the spread of the wingless apple-lice species. But it would take a stiff breeze thus to waft the body of our plump dweller on the alder, unless, indeed, in his younger days.