THE BLISTER FLY AND THE OIL BEETLE. 619 



at all events after dusk — the male regainiDg the natural ascendency 

 by the light of day. Either through books or by actual observation 

 almost every one is familiar with the Glow-worm, and would recognize 

 its pale green-blue light on a summer's evening. Many, however, if 

 they came across the insect by day, would fail to detect the brilliant 

 star of the night in the dull, brown, grub- 

 like insect crawling slowly among the 

 leaves, and still fewer would be able to 

 distinguish the male, so unlike are the 

 two sexes. 



It has often been said that the female 

 alone is luminous. This, however, is an 

 error, as I have caught numbers of these 

 beetles of both sexes, and always found The Glow-worm {Lampyris 

 that the males were gifted with the power noctiluca). 



of producing the peculiar phosphorescent . a e. . ema e. 



light, though in a much smaller degree than their mates, the light look- 

 ing like two small pins' heads of phosphorus upon the end of the tail. 

 Seen by day, the male is a much handsomer-looking insect than the 

 female, being soft brown in color, long-bodied, and wide-winged, alto- 

 gether beetle-like ; while the female is more like a grub than a perfect 

 insect, has no wings at all, and only the slightest indications of elytra. 

 The larva of the Glow-worm feeds upon molluscs, especially upon 

 the smaller snails, which it is able to devour even when retracted with- 

 in the walls of the shell. 



The Blister Fly, sometimes called Spanish Fly, is the typical 

 species of the Cantharidse family. 



It is by no means a common species in England, though it has oo- 

 casioually appeared in -considerable numbers. In such cases, however, 

 it is extremely local, and does not appear to be dis- 

 seminated through the country. Spain is famous 

 for the multitudes of Blister Flies which are found 

 within its limits, and the whole of South-western 

 Europe is prolific in this remarkable beetle. 



The Spanish Fly is a handsome insect, nearly an 

 inch in length, and of a rich silken green, with a 

 gold gloss in certain lights. 



The Oil Beetle belongs to the same family, and 



is very common in England. This name, by which 



"^SpIni^h Fly (a?n^ ^^ ^® popularly known, is appropriate, because, when 



iharis vesicatoria). handled, it has the property of pouring a yellowish 



oily fluid from the joints of its legs. 



The abdomen is extremely large in proportion to the rest of the 



body, and the short diverging elytra descend but a very little way 



