206 



NATURAL HISTORY. 



are somewhat important to the farmer, from the predaceous habits of their 

 larvae, some destroying the young of many injurious insects ; but the 

 species figured sometimes proves injurious, as it frequently occurs in bee- 

 hives, where it eats the bees and spoils the honey, by making 

 its nest in the comix 



Far more interesting than these forms are the fire-flies, 

 with whose appearance all are familiar ; but whose light is 

 still a puzzle to students. The luminous qualities are not 

 confined to the adult flying beetles, but are found in the eggs 

 and larvae as well. One will frequently find on a damp 

 summer evening a worm-like creature crawling in the grass, 

 i.-Bee-par- w hi cn gives off a soft phosphorescent light ; this is a glow- 

 worm, either the larva or wingless female of a .fire-fly. In 

 the adult fire-flies the luminous organs may be either on the upper or the 

 under surface of the abdomen, but are inside the integument, These 

 organs are rather large, and are well supplied with air-tubes, thus allowing 



Fig. •Jin 



asite 



Fig. 20'2. — Glow-worms and fire-flies. 



a rapid oxidation of the tissues, but what the substance is which is burned, 

 no one has yet found out. The light has been studied with the spectro- 

 scope, and found to consist of rays with but little thermal or actinic effect 

 but which greatly affect the visual organs. The spectrum is continuous. 



Our fire-flies are small in comparison with some of the tropical forms. 

 In Central and South America are species which reach a length of between 

 one and two inches, and have light-giving powers to correspond. Tins 

 phosphorescent capacity is not, however, confined to the true fire-flies; but 

 is shared by some members of the group of spring-beetles now to be taken 

 up. One of these species, the cucuyo or cucujo, of Spanish America. 

 reaches a length of an inch and three-quarters, and is the most highly lumi- 

 nous insect known. In the daytime it is not attractive in appearance, as it 

 is a dirty brownish black ; on the sides of the thorax are the oval lanterns, 



