ANNULOSA: INSECTA. 



353 



less, and they differ solely in the armature of the head. The duties of the 

 workers are to ' ' build, make covered roads, nurse the young brood from 

 the egg upwards, take care of the king and queen, who are the progeni- 

 tors of the whole colony, and secure the exit of the males and females when 

 they acquire wings, and fly out to pair and disseminate the race." The 

 duties of the soldiers are to defend the community from all attacks which 

 may be made upon its peace, for which purpose the mandibles are greatly 

 developed. 



SUB-CLASS III. HOLOMETABOLA. Metamorphosis complete; 

 the larva, pupa, and imago differing greatly from one another 

 in external appearance. ' The larva vermiform, and the pupa 

 quiescent. 



ORDER VIII. APHANIPTERA. Wings rudimentary, in the 

 form of scales, situated on the mesothorax and metathorax. 

 Mouth suctorial. Metamorphosis complete. 



This order comprises the Fleas (Pulitida), which are para- 

 sitic upon different animals. The larva of the common Flea 

 (Pulex irritans, fig. 187) is an apodal grub, which in about 



Fig. 187. A, The common Flea (Pulex irritans] ; B, Larva of the same ; C, Pupa of 

 the same. All the figures are greatly magnified. (After Westwood.) 



twelve days spins a cocoon for itself, and becomes a quiescent 

 pupa, from which the imago emerges in about a fortnight 

 more. 



The Chigoe or Sand-flea (Sarcopsylla penetrans) of the tropi- 

 cal parts of America, is a more serious pest than the common 

 Flea. It is, however, only a parasite as regards the impreg- 

 nated females ; the males, unimpregnated females, and larvae 

 leading a free existence. The impregnated females, however, 

 bore their way through the skin of the foot in the human sub- 

 ject, and live there till they assume the size of peas, by the 

 distension of the abdomen with eggs, often occasioning great 

 local irritation and inflammation. They also live beneath the 

 skin of mice and dogs. 



Many authorities regard the Aphaniptera as a degraded group 

 of the Diptera. 



z 



