INSECTS MAYFLIES AND DRAGON-FLIES 185 



the perfect insect, but without wings. The adult insect is " stone-coloured " ; 



one of them, Perla bicaudata, is well known as a good bait for trout and 

 other fishes. 



Order V. ISOPTERA. 



None of these occur in Britain ; the White Ant, or TERMITE, is the 

 representative. 



Order VI. CORRODENTIA. 



Under this order come the Book-lice and Bird-lice. The former are minute, 

 soft-bodied insects, which never develop wings. Atropos divinatoria is common 

 in damp houses. Some damage books and papers, and others destroy en- 

 tomological collections. The Bird-lice are also wingless, and spend their lives 

 on the plumage of birds or the fur of animals, feeding on the delicate feathers 

 and hairs. 



Order VII. EPHEMEROPTERA. 



Mayflies. These insects, familiar to all dwellers by streams and rivers, 

 are a very large family more than 300 species in all parts of the world. Their 

 adult form is very peculiar, owing to the fragile wings (very delicate and beauti- 

 ful), their two or three long tails or cerci, and their short bristle-like antennae. 

 The mouth parts are very undeveloped, and in some cases absent altogether, 

 which means that the adults do not feed. Indeed, they require no food, since 

 they live for a few hours only " creatures of a day," as their name Ephemera 

 signifies. Within a single twilight, it may be, they dance jerkily up and down 

 over the water, in a characteristic flight, deposit their eggs, and fall dead ; but 

 some two years are spent in the earlier stages. Their eggs, united into a little 

 mass, are allowed to fall into the water, where the larvae burrow into the mud, 

 feeding on decaying vegetation ; the pupa, or nymph, also is aquatic, and leaves 

 the water to change into the adult form. This is called a " false imago," kn, vm 

 to anglers as the "Green Drake." Within a short time the skin splits, and 

 the true imago emerges, being called by fishermen the "Grey Drake." The 

 commonest are Ephemera vulgata and E. danica. 



Order VIII. ODONATA. 

 Here we meet the 



DRAGON-FLIES, 



more than forty species of which are found in Britain. Their shape and 

 form are well known, the characteristics being a very large head, which can 

 be moved freely ; enormous compound eyes, consisting of thousands of lenses, 

 and three simple eyes on the forehead or brow ; remarkable mouth parts, 

 formed for biting, the jaws or maxillae forming a kind of trap for holding the 

 insects on which the Dragon-fly feeds ; a thorax, which slopes forward so that 



