162 



BRANCH ARTHROPODA 



The chig'oe, a small flea of the West Indies and of South America, often 

 causes serious trouble by burrowing under the toe-nail or the skin of the foot 

 of man. The female burrows under the skin, becomes encysted and dis- 

 tended by the eggs which hatch here, and unless the young are carried out 

 by the pus they probably develop here. 



Fig. 133. — Common cat and dog flea (Pi'i'lex serrdt'iceps) : a, Eggs; h, 

 larva in cocoon; c, pupa; d, adult; e, mouth parts of same from side; /, 

 labium of same from below; g, antenna of same; all much enlarged. (How- 

 ard, Bull. U. S. Dept. of Agriculture, 1896.) 



Rat Fleas. — It is believed that in tropical countries the disease germs 

 of the bubonic plague may be transmitted from rats to men by the bites or 

 punctures of rat fleas. 



ORDER XI. LEPIDOP'TERA 



This order includes such common insects as butterflies and 

 moths or " millers." There are more than 6600 species in 

 North America. 



The head is rather small for the size of the body. 



The mouth parts are highly complex, a striking example of 

 adaptation of structure to function. The two maxillae are greatly 

 modified into a long hollow tube (Fig. 141) for sucking the juices 

 of fruits or the nectar of flowers. \Yhen not in use this tube, 

 tongue, or proboscis is coiled up between two projections, the 

 labial palpi. Many moths do not feed in the adult stage and 

 the maxilte are lacking. The other mouth parts are mere 



