Insects and insecticidesA practical manual concerning noxious insects and the methods of preventing their injuries . -beetle. Doryphora decemlineata. This insect originally lived upon a wild variety of•Solanum (the genus to which the cultivated potatobelongs) in the West, near the base of the RockyMountains. It was not known as an injurious spe-cies until about 1860, when it attacked potatoes inthe gardens of settlers in Kansas and neighboringstates, and thereafter gradually spread eastwarduntil it finally reached the Atlantic coast, and wascarried across to Europe, becoming extremely destruc-
Insects and insecticidesA practical manual concerning noxious insects and the methods of preventing their injuries . -beetle. Doryphora decemlineata. This insect originally lived upon a wild variety of•Solanum (the genus to which the cultivated potatobelongs) in the West, near the base of the RockyMountains. It was not known as an injurious spe-cies until about 1860, when it attacked potatoes inthe gardens of settlers in Kansas and neighboringstates, and thereafter gradually spread eastwarduntil it finally reached the Atlantic coast, and wascarried across to Europe, becoming extremely destruc-tive wherever it apjDeared. The adult Colorado Potato-beetle (Fig. 87, d) istoo familiar to American gardeners to need descrip-tion here. Its orange-colored eggs (a) are depositedin masses, varying in number from a dozen to fifty 170 INSECTS AFFECTING THE POTATO. or more, on the under surface of the potato leaf, andoccasionally also upon the leaves of grass, smart-weed, or other plants in the potato field. Theyhatch about a week later into peculiar little grubs;(b) that feed upon the foliage a few weeks. They. Fig. 87. Colorado Potato-beetle: a, a, eggs; 6, 6, larvae; c, pupa; d, d, bee-tles ; e, wing of beetle, magnified. then descend to the ground, where just beneath thesoil surface, or under rubbish above it, they changeto pupa? (c). About ten days later they emerge asperfect beetles. There are from two to four annualbroods, the number varying with the latitude; andthe insect hibernates in the beetle state. Like most other insects, the Colorado Potato-beetlefluctuates greatly in numbers and any given locality it will be very destructive fora period of years, and then there may be severalseasons when its injuries will hardly be noticed. INJURING THE LEAVES. 171 This oscillation is probably due to the variousnatural enemies of the insect. Remedies.—The standard remedy for this pest isthat of spraying or dusting with some form of arsenic,,such as London p
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