FAM. 78. CHRYSOMELIDAE.—_Antennae moderately long; eyes moderately large, usually not at all surrounding the insertion of the antennae; upper surface usually bare, frequently brightly coloured and shining._ This enormous family comprises about 18,000 species of beetles, in which the form and details of structure are very varied. No satisfactory character for distinguishing Chrysomelidae from Cerambycidae has yet been discovered, although the two families are certainly distinct and natural. Most of the Chrysomelidae live on foliage; few of them are more than half an inch long, whereas the Cerambycidae are wood-feeders and usually of more elongate form and larger size. The potato beetle, or Colorado beetle, that occasioned so much destruction in North America some thirty years ago, and the introduction of which into Europe was anticipated with much dread, is a good example of the Chrysomelidae. The turnip flea, a tiny hopping beetle, is among the smallest forms of the family, and is a member of another very extensive subdivision of Chrysomelidae, viz. Halticides. The term Phytophaga is by many naturalists limited to Chrysomelidae, the Cerambycidae being excluded. The classification of the family is but little advanced, but the enormous number of species of Chrysomelidae are placed in four divisions, viz.:— [Illustration: Fig. 142—_Doryphora decemlineata_, the potato beetle. North America. A, Imago; B, hind-tarsus. 3, third joint; 4, true fourth joint; 5, so-called fourth joint.] {279}Prothorax much narrower at the base than the elytra, and usually without side-margins (raised edges). Sub-fam. 1. Eupoda; with three divisions, Sagrides, Donaciides, Criocerides. The basal ventral plates of the abdominal segments are somewhat shorter in the middle than at the sides, the fourth one being often invisible in the middle, while the fifth is very large. Sub-fam. 2. Camptosomes; with six divisions, Megascelides, Megalopides, Clythrides, Cryptocephalides, Chlamydes, Sphaerocarides. In the other two groups there is no great disparity between the fourth and fifth ventral plates. Prothorax not greatly narrower at the base than the elytra, and usually with distinct edges at the outsides. Sub-fam. 3. Cyclica; with four divisions, Lamprosomides, Eumolpides, Chrysomelides, Galerucides. Front of the head bent downwards or inflexed, so that the mouth is on the lower aspect. Antennae inserted close together on the most anterior part of the head, so that they are more forward than the mouth. Sub-fam. 4. Cryptostomes; with two divisions Hispides, Cassidides. In the other three divisions the mouth is placed as usual, but the insertion of the antennae varies a good deal. The larvae of about 100 species of the family are known; they are arranged in accordance with their habits, by Chapuis,[145] in six groups, viz.: 1. Elongate larvae, living under water, and there undergoing their metamorphosis. (Donaciides.)