276 



THE BIOLOGY OF INSECTS 



American D. palmata, the larvae of which descend to the 

 bottom and feed on the underground stems and roots of 

 the water-lily (Fig. 68). The eggs of other species are laid 



Fig. 69. — Structural details of larva of Donacia. A, head dissected 

 from below : a, feeler ; md, mandible ; ab, ad, its abductor and adductor 

 muscles; la, labrum ; gn, suboesophageal ganglion, X 70. B, Front 

 of head dissected from above : p, palp of maxilla ; g, galea ; /, base, and 

 /', point of lacinia ; m, lacinial muscle; h, hypopharynx ; o^, gullet, 

 X 70. C, longitudinal section through tail-spine and adjacent region 

 of abdomen ; t, trachea ; c, closing lever ; a, atrium ; p, passage to 

 canals, X 100 ; D, tail-spine in longitudinal horizontal section. E, dorsal 

 view: s, spiracular slit; d, dorsal, and /, lateral canals, X 100. After 

 A. G. Boving (Int. Rev. Hydrobiol. 1910). 



in masses or singly on various aquatic plants whence the 

 newly hatched grubs make their way downwards into the 



