National Geographic : 1929 Jul
INSECT RIVALS OF THE RAINBOW The round-headed apple-tree borer is per haps the worst pest among the Cerambycids. In its adult form, it is about three-fourths of an inch long, with two creamy stripes along its brown back from mouth to tail. It deposits its eggs on the bark at the base of the tree it ex ploits in June and July. These hatch in a few days and the tiny grub works its way into the soft sapwood under the bark. After its fine chisellike mandibles get the temper of age, it begins to tunnel its way into the heart of the tree, swallowing the borings of the tunnel as it goes. Finally, after three years of eating a path through the wood, it di rects its operations toward the surface. Just before reaching the outer air, and leav ing only a tiny membrane ahead of it to be rup tured when it wakes up from its transformation sleep, the grub excavates a nice little chamber, which it carefully lines with smooth, soft mate rials made from wood fiber, and then lies down for its change-working nap. After two or three weeks of unconsciousness, it awakens no longer a grub, but a fully accoutered long-horn. The oak pruner has a different method of attack. It lays its egg on a tender twig. When the grub hatches, it enters the twig and feeds on its juicy fiber. As it grows, it relishes a harder diet, so it bores its way into a mature limb, which it finally cuts so thoroughly that when a high wind comes it is blown to the ground. The limb thus acts as a parachute for the grub, allowing it to reach the ground safely. It now uses the severed limb both as a food supply and a habitation. The oak pruner also attacks other trees. Some species of Cerambycid larvae remain in wood for surprising periods. After timber is cut and dried and used in the building of houses or the manufacture of furniture, it lacks nutritive qualities, and the growth of the wood boring grub is so arrested that it often requires many years for the attainment of maturity. I have seen them issue from a porch column that had been standing twenty years, and recently a western college professor reported the issu ance of one from the wood of a bookcase that had been in his family for nearly fifty years. The species reproduced are: Saperda can dida Fab. (Plate XVIII, figure 7), found in North America; Sternotomis virescens Westw. (Plate XX, figure I), an African species; Cri oprosopus magnificus LeConte. (Plate XX, fig ure 2), from Arizona; Sternotomis mirabilis Drury. (Plate XX, figure 3), found in the Af rican Gold Coast; Tragidion fulvipenne Say. (Plate XX, figure io), found in central and western United States; Sternotomis bifasciata Fab. (Plate XXI, figure I), found in West Af rica; Dendrobias reducta Casey. (Plate XXI, figure 4), habitat southern California; Cyllene decora Oliv. (Plate XXI, figure 5), habitat southeastern and central United States; Des mocerus palliatus Forst. (Plate XXI, figure 7), a native of eastern United States; Stenaspis verticalis Serv. (Plate XXII, figure 2), found in Texas, Arizona, and Mexico; Callichroma schwarzi Fisher. (Plate XXII, figure 5), found in Texas. Tiger-beetle Family (Cicindelidac). The tiger-beetles are fast runners and quick flyers, and in the larval stage live up to their name, being carnivorous and voracious eaters. In that stage they are uncouth grubs, with big heads and sturdy jaws. They usually dig burrows in the ground, and lie in wait at the entrance for some unfortunate insect that chances to pass that way. In catching their prey the tiger beetles' larvae seize the victims with their long, sharp mandibles, and drag them to the bottom of the burrow, where they are eaten at leisure. The larva is provided with a little hump on the fifth segment of the abdomen, on which are two strong, forward-curving hooks. These it uses to hold itself firmly in position while attacking a victim, lest the latter give a sud den jerk and pull the "bushwhacker" from its hole. The adult beetles catch their victims and drink the blood after the fashion of a weasel. With their big eyes, long legs, sharp mandibles, and fleet movements, the tiger-beetles are identified easily. The species reproduced is: Cicindela scutel laris Say. (Plate XVIII, figure 8). It ranges between Texas, Arkansas, Nebraska, and Wy oming. Lady-bird Beetle Family (Coccinellidae). Perhaps no beetle clan surpasses the lady-birds as friends of man. Their pretty polka-dot wing cases and their gentle demeanor are in keeping with their beneficent relation to man. But to certain of our insect foes the larvae of this family are veritable roaring lions and stalking tigers going about seeking whom they may de vour. Plant-lice, scale insects, and many others of the "wee beasties" of insectdom the lady birds destroy by the billions. The larvae are more active than beetle grubs usually are, running about on plants in search of game. They ordinarily "change their clothes" three times before reaching maturity, some times changing their color in doing so. They spend four or five weeks in the larval stage; the eggs are laid on the bark, stems, and leaves of the trees or plants they visit, and hatch in a few days. There are about 2,000 known species of lady birds in the world, of which about 150 species are natives of America. Some have the curious habit of congregating in great masses on moun tain tops, to spend the winter, once they have gotten their wings. California fruit growers collect them, and put them in cold storage where they are retained until they are needed for keeping down plant-lice the following sum mer (see illustration, page 9). The species reproduced is: Epilachna bore alis Fab. (Plate XVIII, figure Io), which ranges over North America and Mexico. Scavenger Beetle and Leaf Chafer Fam ily (Scarabacidae). The Scarabaeid family has two branches, well differentiated by their hab its-the scavengers, of which the tumble bug or dung beetle is typical; and the leaf chafers, of which the rose bug or rose chafer is a repre sentative species.