Page:The American Cyclopædia (1879) Volume XIII.djvu/793

 POTATO BUG- 769 through Nebraska to the western borders of Iowa, and in the following two or three years it spread itself over the entire extent of this latter state. Its natural history was first made known in 1863, in an article published in the " Prairie Farmer " by Prof. 0. V. Riley. By 1865 it had crossed the Mississippi, con- tinuing its ravages in the potato fields of Illi- nois and Wisconsin. From these states, in 1867, it invaded western Indiana and the S. W. corner of Michigan, and in 1868 made its appearance in Ohio; and advancing at con- stantly accelerated speed, it reached the At- lantic states in 1874, and the seabord in 1875. As its native home is subalpine, it naturally thrives best in the north, and in its eastward march it has been observed that its southern col- umns lag far behind the northern ones. This is accounted for by the fact that the heat and drought of midsummer in the southwestern states prove inimical to it in its immature stages. This insect is not itinerant in the true sense of the word. It does not march through a country, but in every locality where it makes its advent it establishes a permanent colony. It usually proves most injurious the first year or two after its appearance. Subsequently its numbers are much reduced by the attacks of parasitic and predaceous insects which follow it, or by degrees acquire the habit of preying upon it. The Colorado potato beetle hiber- nates in its perfect state beneath the surface of the ground. It has been exhumed from depths varying from a few inches to several feet, though its habit is not to burrow deeper than 10 inches. The beetles issue from the ground early in May. They fly readily during the heat of the day, and are able to make jour- neys of considerable extent. They begin lay- ing their eggs upon the young potato plants as soon as the latter appear above ground, and will often work into the ground to feed upon the young leaves before these have fairly shown themselves. The eggs are oval, of a translu- ent dark orange color, and are deposited in lusters of from 10 to 40 on the under sides of le leaves. The larvae are hatched in less than week, and are at first of a dark Venetian red, oecoming lighter and acquiring a double row of black lateral spots as they approach matu- rity. The legs, head, and posterior half of the first joint are also black. In from two to three weeks these larvae acquire their full growth, after which they enter the earth and undergo their transformations, first to the pupa and then to the beetle state, which last is assumed in about a month from the time of hatching. There are three broods or generations each year in the latitude of St. Louis, yet it may be found at almost any time during the sum- mer in all its different stages. This is owing to the fact that the eggs in the ovaries con- tinue to develop, and are laid in small batches at short intervals during a period of about 40 days in summer. The number produced by a single female averages from 500 to 700. This insect, at first confined to plants belonging to the genus solanum, has in its eastward pro- gress acquired the habit of feeding on several other plants belonging to different genera or even to different families; among these are the cabbage, hedge mustard (sisymbrium offi- cinale), smartweed (polygonum hydropiper), pigweed (amarantus retroflexus), thistle (cir- sium mullein (verbascum), lamb's quarter, and maple-leaved goosefoot (chenopodium al- bum and C. hybridum). But it is doubtful whether it would thrive for any length of time on any plant not belonging to the nightshade family (solanacece). As the insect advanced toward the Atlantic, it met with new enemies at almost every step, and these are often so efficient in aiding man in his warfare against it that the farmer should be well acquainted with them. Upward of two dozen of these enemies of its own class have been enumerated and fig- Fto. 2. Lydella doryphora. (Hair line showing natural size.) ured by Kiley in his Missouri entomological reports. The only genuine parasite known to attack it is a tachina fly (Lydella doryphora, Riley), somewhat resembling in size and gen- eral appearance the common house fly. This fly fastens its tough, oval, white eggs to the body of the doryphora larva, and from them subsequently hatch small maggots, which pen- etrate the body of their victim, and there feed- ing on the fatty portions are carried into the ground when the doryphora descends to un- dergo its transformations, finally causing its death. These flies are sometimes so numerous about an infested potato patch that it is difficult to find an uninfected do- ryphora larva, and the noise they make is like the buzzing of bees. The next most efficient enemy FlG 8 ._Arma spinosa. Of the Colorado potato a . Enlarged beak. ft. beetle is a heteropterous Bug -gsJ*^ insect called the spmed gide s soldier bug (arma spinosa, Dallas). This bug, which is equally carnivo- rous in its larva, pupa, and perfect states, is of an ochre-yellow color, and is represented in fig 3 with a pair of wings closed and the