BEETLES 353 



up from the grass, it is found to be a female, which is of a whitish- 

 yellow colour, without wings, and only possesses very short, scale-like 

 wing-covers. In both sexes four white spots are discernible on the under 

 surface of the body, which represent the luminous organ. Now, what is 

 the use of this luminosity ? In the first place it is a means of recogni- 

 tion for the sexes ; guided by it the male can discover the female, which 

 is incapable of flight, even on the darkest night, whilst the female in its 

 turn will be able to observe any male in its proximity. Secondly, the 

 luminosity very probably serves as a means of frightening enemies ; for 

 we find that the eggs and larvce are also luminous, though in a less degree 

 than the beetle. The larvae are worm-like, slender and active creatures ; 

 they are of predatory habits, living chiefly on snails. Hence, like the 

 beetles, they are mostly found in moist localities. 



Family 7: Blistering Beetles (Vesicantia). 



The Oil Beetle (Meloe proscarabceus) . 



(Length up to 1 J inches.) 



The oil beetle is an insect of very striking appearance. In the spring 

 it may be seen crawling heavily and lazily over the grass, to which its 

 shiny blue-black body stands in sharp contrast. This, however, is in 

 nowise a disadvantage to the insect, which is a vegetable-feeder, and 

 finds its favourite food (grass, leaves of dandelion and other plants) with 

 ease and in abundance, and is, moreover, in the happy position of being 

 avoided by all insect-eating animals. For when touched the insect 

 secretes from the joint between the femur and tibia an acrid, yellow, 

 oily liquid (hence the name), which even the hungriest of insect-hunters 

 shuns with disgust. Investigators have found that this liquid is nothing 

 but the blood of the insect. (Compare with spotted salamander.) This 

 provision, too, enables the beetle to dispense with wings, and the u-ing- 

 covers also are very short. The minute larvae of the oil beetle crawl 

 upon flowers, and thence attach themselves to the bodies of humble 

 and other bees, by whom they are conveyed to their nests, and there 

 they live as parasites and undergo their metamorphosis. As, however, 

 many of the larvae perish in the course of their transportations, the 

 number of eggs produced by the beetle is very large, as may be seen by 

 the bulky, distended abdomen of the female. 



A closely-allied species is the Spanish Fly (Lytta vesicatoria). It is 

 about f inch long, and metallic green in colour, thus presenting but a 

 slight contrast to the green leaves of the ash and elder on which it lives, 



