BEETLES. 319 



of black spots, the head and feet are black, and there is a ring of the same color upon 

 the second segment. The head and legs of D.juncta are, on the contrary, pale, and 

 they have but one row o'J black dots on each side. The larvae of the Colorado potato- 

 beetle attain their full growth in from fourteen to eighteen days, and go under ground 

 to pupate, where they form a naked yellow pupa. The pupal state lasts about ten 

 days, so that only about a month is required for all stages together, from the egg to 

 the perfect beetles. This enables these insects to have from two to four broods yearly, 

 and as the females do not lay their eggs all at one time a succession of larvae is pro- 

 duced, so that one may find the species in every stage of growth at any time during 

 summer and autumn. Both beetles and larvae feed on the same plant. The beetles 

 hibernate underground and lay eggs the next spring. 



The immense armies of these beetles which have at times attacked potato-fields, 

 where they could be gathered by measure rather than by number, have rendered them 

 a serious pest to farmers, and their actual destruction of whole fields of a vegetable 

 almost necessary to human existence in some countries has caused Doryphora to be 

 the subject of much careful investigation, and of some legislation. European nations 

 have sometimes prohibited the importation of American potatoes, and fines have been 

 imposed in England for possessing living Colorado potato-beetles. 



The sudden spreading of D. clecemlineata over an area of about 1,500,000 square 

 miles has not only been accompanied by a change of food-plant from one species of 

 Solanaceas to others, but even to plants of other families. It will eat, when potatoes 

 are not at hand, cabbage, common thistle (Cirsium lanceolatum), pigweed (Amarantus 

 retroflexus), hedge-mustard (Sisymbrium qfficinale), and numerous other plants, and 

 when absolutely compelled by hunger it has been known to eat grass and the cultivated 

 oat. Most all widely distributed insects are subject to considerable variation ; the 

 Colorado potato-beetle forms no exception, and the fact of its extensive distribution 

 in so short a period as twenty-five years in portions of America having considerable 

 diversity of climate, together with the variations consequent upon difference of food- 

 plants to which it has accommodated itself, makes these variations of pattern, color, 

 and size furnish, as Dr. Riley has observed, "interesting material for the close species 

 makers," and indicates a fertile field of investigation of the variations which twenty- 

 five years or less of changed environment can produce in a species the whole history 

 of the spread of which is comparatively well recorded. 



As Doryphora itself spread like a wave of destruction over the country, for the 

 first few years its depredations in any region were scarcely hindered, but later, while 

 man was learning how to poison it, lower animals were developing a taste for it. The 

 lady-birds attack the eggs and larvae ; numerous species of Hemiptera, such as Podisus 

 spinosus and Harpactor cinctus, suck out the juices of the larvaa ; a fly (Lydetta dory- 

 phorce) lives in its larval state as a parasite within the larvae of Doryphora, and has 

 been found so abundant in places as to nearly exterminate the beetle ; and the eggs 

 and larvae are eaten by several beetles, among which Lebia grandis once not very 

 common has apparently increased in numbers on account of the food-supply which 

 Doryphora furnishes. The above-mentioned insects are selected from over two dozen 

 species known to attack Doryphora. Among wild birds the crow, quail, rose-breasted 

 grosbeak (Goniaphea ludoviciana), and cardinal grosbeak ( Cardinalis virginianus) ; 

 and, among domesticated birds, the duck, devour these beetles. In some cases chickens 

 have acquired the habit of feeding upon them, and the common toad does good service 

 in eating large numbers of them. 



