510 THE INSECT WORLD. 



spontaneously or under the influence of artifical excitement. Some 

 chemical experiments have been made to ascertain the nature or the 

 composition of the humour which produces this strange effect ; but 

 up to this moment, they have only enabled us to discover that the 

 luminous action is more powerful in oxygen, and ceases in gases 

 incapable of supporting combustion. In the most common species, 

 the Lainpyris 7ioctihica, or glow-worm, the phosphorescence is of a 

 greenish tint : it assumes at certain moments the brightness of white- 

 hot coal. 



The females have no wings, while the males have them, and 

 possess very well-developed elytra. The females resemble the 

 larv^ much, only they have tlie head more conspicuous, and the 

 thorax buckler-shaped, like the male. The larvze feed on small 

 molluscs, hiding in the snails' shells, after ha\'ing devoured the 

 inhabitant. They also possess the phosphorescent property in a less 

 degree than the adult females. The female ,pupa resembles the 

 larva ; the pupa of the male, on the contrary, has the wings folded 

 back under a thin skin. The perfect insect appears towards the 

 autumn. 



The Glow-worm {^Lampyris iioctiluca, Fig. 550) is of a brownish 

 yellow. It is comm.on in England. In a kindred species, the 

 Luciola Italica, the two sexes are ^\inged, of a ta\vny-bro\\'n, and 

 equally phosphorescent. They are met with in great numbers in 

 Italy, and the lawns are covered with them. Other insects of this 

 family are without the faculty of emitting light ; as, for example, the 

 genus Lycus, of brilliant colours, which are met with in Africa and 

 India. One of the finest is the Lyciis latissimus. 



Drilus is another genus, comprising insects of very singular 

 habits. The t}^pe is the Drilus flavesce7is. The male — a quarter of 

 an inch long, black and hairy, with elytra of a testaceous yellow, and 

 \^dth pectinated antennae — for a long time was alone known. The 

 female — from ten to fifteen times as large, ^\athout wings and elytra, 

 of a yellowish brown — was not discovered till much later, having 

 apparently nothing in common ^^^th the male in shape or colour. 

 The metamorphoses of these curious insects are now perfectly under- 

 stood. ]Mielzinsky, a Polish naturalist established at Geneva, 

 found the Drilus in the laiwa state in the shell of the Helix ?iemoralis. 

 These lar\-3e devour the snail whose dwelling they occupy, as do the 

 larvae of the Lampyris. iNIielzinsky saw them emerge, but obtained 

 only females, which differed scarcely at all from the larv^ from which 

 they proceeded. He made a separate genus of them, under the 

 denomination of Cochleoctonus, and called the species Vorax. Later, 



