Beetles 



247 



It would be reasonable to expect to find the insects of an order so pursued 

 by collectors susceptible of ready classifying and determining. On the 

 contrary, no order presents more difficulty to the elementary and even 



labial palpi 



labium 



compound eye- 



mouth-parts 



_./- --maxillary palpi 



head 



antenna. 



..mesotkorax 

 metathorax 



coxa- 

 trochanter 



tarsal segmeii{s 



abdomen 



FIG. 338. Ventral aspect of male great water-scavenger beetle, Hydrophilus sp. 

 (Three times natural size.) 



advanced students of systematic entomology. The tables and keys pre- 

 pared by the few specialists really competent to determine accurately the 

 different species of beetles are as nearly impossible to the amateur and 

 elementary student as any "keys" in al. the field of classific entomology. 



