Blister-beetle,

Blister-beetle, a popular name for a number of beetles in a family of Coleoptera known as Vesicantia, or in two distinct families, Meloide and Cantharidae. The name refers to the vesicating or blister-raising properties of their body-juice. The Spanish-fly and the Oil-beetle are familiar illustrations. As to the zoological characters of the family, the antennæ are usually 11-jointed, the head depressed with a narrow neck, the front shield narrower than the flexible wing-covers, the claws split into two usually unequal portions, the abdomen with 6 to 7 free rings. They are usually brightly coloured, especially at home in warm countries, include about 800 species, and almost always possess the blistering property above noticed. The life-history is often very remarkable. The larvæ live parasitically on bees, on grass-hopper or locust eggs, &c., and seem to pass through an unusual number of changes, to which the name 'hyper-metamorphosis' has been applied. It is not merely that the larvæ begin life lean, horny, and 6-footed, and soon become fat, soft, and footless, but that before passing into the pupa stage, they pass through a series of preparatory changes. The important genera are: (1) Lytta or Cantharis, (2) Mylabris, (3) Cercocoma, (4) Meloë. In regard to some of these, a few notes are requisite. (1) The genus Lytta or Cantharis has wings, long, thread-like, 11-jointed feelers, and kidney-shaped eyes. It includes over 250 species, of which only 8 are European. The most familiar form is the common blister-beetle or Spanish-fly, Lytta or Cantharis vesicatoria. This bright golden-coloured or bluish-green beetle is common on many trees in Europe. It makes its presence felt by devouring the leaves. The females lay a large number of eggs in a hole in the ground, whence, after 3 to 4 weeks, the larvæ pass in all probability into certain bees. For medicinal purposes, the beetles are dried and rubbed into powder. The irritant substance is found throughout the body, but especially in the ovaries. (2) Mylabris is a rarer European genus, but includes even more tropical forms than Lytta, restricted, however, to the Old World. (3) Cercocoma, with 9-jointed feelers, is commoner in Europe; C. schäfferi is indeed frequent. (4) Meloë is a large wingless genus, with about 70 species, represented everywhere except in Australia. The females have a very broad abdomen. They live in grass. On irritation, they allow an oily, yellow, blistering fluid to ooze out from between the joints. The common Oil-beetle (M. pro-scarabæus) and another beautiful species (M. variegatus) are striking illustrations of romantic life-histories. For this and other particulars in regard to Meloë, see article under that head. Apart from their medicinal use, the physiology and life-history of these blister-beetles invest them with very considerable biological interest. The common blister-beetle, Spanish-fly or Cantharis, will be further treated at CANTHARIDES; and see below.