82 Bulletin American Museum of Natural History [Vol. XLII 



a genus possessing larval prolegs and manifesting a relationship to the 

 eruciform type of larva. 



Anccena and Paracymus, with the gradual reduction of legs, lead 

 through Cyloma 1 to the terminus terrestre, the subfamily Sphseridiinse. 



IV. KEYS 



An attempt is made to separate the genera in their immature stages. 

 Schiodte, 1862, gave excellent keys, written in Latin, for all the stages, 

 butt hey are necessarily incomplete. The main divisions of his pupal kej^ 

 have been incorporated here. The only contemporary work of note is 

 the larval key given by d'Orchymont, 1913. His grouping of the genera 

 is a very natural one; however, on account of additional material, new 

 keys have been considered advisable. Representatives of all the genera 

 have been examined with the exception of Cercyon, the data for which 

 have been taken from literature. 



Key for the Identification of the Egg-cases 



1. Eggs laid singly .2. 



Eggs laid in a mass 5. 



2. Covered with silk, either closely or loosely applied 3. 



Entirely naked Ochthebius (in part); Hydroscapha. 



3. Silk loosely applied, eggs visible Ochthebius (in part); Limnebius. 



Silk closely applied, only contour of egg visible 4. 



4. Eggs not entirely enclosed, with only a blanket-like covering, nearly regular 



in outline, oval Hydrwna. 



Egg entirely enclosed, irregular in outline, with little stanchions. .Hydrochous. 



5. Egg-mass covered with closely applied silk, eggs invisible 6. 



Egg-mass covered with silk, eggs visible 17. 



6. With a prominent projection at the cap end (armed) 7. 



Without a prominent projection (unarmed). The projection, if present, is 



represented only by small strands 14. 



7. Projection ribbon-like 8. 



Projection spine-like 12. 



8. Projection tubular 9. 



Projection flattened '. 11. 



9. Tubular projection opened distally Helophorus. 



Tubular projection closed distally 10. 



'The Cyloma larva is not known, but the adult, according to Ganglbauer, shows the relationship 

 of the Hydrobiini to the Sphceridiinae. 



