404 TEXT-BOOK OF ZOOLOGY 



elongated, active animal with three long bristles at the end of its 

 abdomen. From its covering of silvery scales and a preference for 

 sugar it has obtained its names ; but it also feeds on wool, paper, and 

 similar substances. 



On the surface of standing water we often find thousands of minute 

 black creatures which execute powerful jumps by means of a fork-shaped 

 appendage on the penultimate abdominal somites, for which reason they 

 are called Water Springtails (Podura aquatica). 



One of their nearest relatives, the Glacier Flea (Dcsoria glacialis), 

 inhabits the icy waters of Alpine glaciers. It is only during the summer, 

 when the sun throws its burning rays upon the glaciers, melting ice 

 and snow, that this peculiar insect is astir in the daytime, becoming on 

 each succeeding night once more rigid with the cold. 



CLASS II. : MILLIPEDES AND CENTIPEDES (MYRIAPODA). 



WINGLESS articulated animals, breathing by tracheae ; body consisting of 

 two divisions, the head and trunk ; head provided with a pair of antennae 

 and two or three pairs of jaws ; the body usually elongated, nearly every 

 segment carrying one or two pairs of legs. 



Millipedes are not infrequently discovered in dark, moist places, 

 especially under stones and moss. They are all of nocturnal habits, and 

 therefore of obscure colour. The body, being long and wormlike, requires, 

 like a lepidopterous caterpillar (see p. 319), a large number of legs for 

 its support (though there never are so many as a thousand, as the name 

 implies). All the somites of the body being equally equipped with legs, 

 and wings being never developed, none of the somites coalesce to form a 

 distinct thorax, as is the case in (typical) insects (see p. 311). On the 

 other hand, there is always a distinct cephalic division, or head, which 

 supports the masticatory mouth parts, and carries the antennae and 

 numerous ocelli, or simple eyes (see p. 317). All the species multiply by 

 means of eggs. Of the millipedes which come under our notice, two 

 groups may be easily distinguished : 



ORDER I. : CENTIPEDES (CHILOPODA). 



THESE are rapid, furtively-moving creatures, with broad, ribbon- shaped 

 body and a resemblance to wood lice (which see). The pliancy of their 

 body and length of the legs, of which each segment carries a pair, 

 endow them with that rapidity and nimbleness of movement required by 

 their predatory mode of existence. The size and strength of their mouth 

 parts are similarly adapted to this mode of life. By means of poisonous 

 bites these nimble creatures can overpower animals much their superiors 



