650 



ZOOLOGY 



SECT. 



adults in their food and mode of life ; very generally the jaws are 

 adapted for biting, even when the mouth of the adult is suctorial. 



FIG. . r >29. A E, ventral view of five stages in the development of Hydrophilus. a and 1>, 

 points at which the blastopore first closes ; af. edge of the amnion fold ; af, caudal fold ; af", 

 paired head-fold ; an. antenna ; ex, terminal segment ; g, pit-like invagination to form the 

 rudiment of the amnion cavity ; /, procephalic lobes ; ;, groove-like medio-ventral in- 

 vagination ; x, germinal bands covered by the amnion. (From Lang, after Heider.) 



B 



FK;. 530. A and B, later stages of the embryo of Hydrophilus with the rudiments of the 

 extremities ; in B the abdominal appendages are visible, a. anus ; an. antenna ; </, rudiment 

 of the ventral nerve-chain; //;. mouth; itnl. mandible; mx^, first maxilla; mx'*, second 

 maxilla; Pi, p-2> J>3> thoracic legs; 7)4, 7(5, 7)7, 7)9, rudiments of the appendages of the first, 

 second, fourth, and sixth abdominal appendages ; st. stigmata ; rX - , prostomium. (From 

 Lang, after Heider.) 



After a longer or shorter period passed in this larval condition, in 

 which it is usually ^active and very voracious, the young Insect 



