OUR HOUSEHOLD INSECTS 



merely younger forms of the latter. A flea has not, 

 throughout its life, the form with which we are familiar, 

 nor does it in that form grow at all. The little fleas 

 are simply the males, which are considerably smaller 

 than the females, in accordance with a rule very fre- 

 quently illustrated amongst insects. The males also differ 

 in shape, and have the hinder end of the body some- 

 what turned upwards (Plate V.). In its life history a flea 



differs totally from a bug : 

 the former is an insect 

 with a complete meta- 

 morphosis, and therefore 

 altogether differently 

 shaped in its larval con- 

 dition, while the latter 

 is almost identical in 

 shape during the whole 

 of its life, and exhibits 

 similar habits through- 

 out ; hence the tiny bugs 

 are really young ones, 

 though this is not the 

 case with fleas. 



The digestive apparatus 

 of a flea (Fig. So) consists 

 of parts very similar in 

 their arrangement and 

 function to those of the 

 cockroach, and therefore 



FIG. 80. Digestive Apparatus of Dog's 



Flea. CB, oesophagus ; g, gizzard ; needs no detailed descrip- 



s, stomach; m, Malpighian tubules; , . 



i, intestine; r, rectum. (After tion. Ihe Oesophagus IS a 



Landois.) r e 



rather short and narrow 



tube, leading into a thick-walled gizzard, which, again, 

 opens by its broader end into a capacious bag, the 



