AQUATIC INSECTS IN THE ADIRONDACKS 4II 



good "as these, serviceable tables for the determination of the adult 

 insects. We give here a table that will serve for distinguishing the orders 

 in the larval stage. So few relatively of the larvae of aquatic insects are 

 known as yet, that this table must be considered tentative as to its state- 

 ments of group characters. 



In all the following tables and descriptions the characters described 

 and the measurements given apply to fully grown nymphs or larvae 

 except when otherwise expressly stated. 



KEY TO ORDERS OF AQUATIC INSECT LARVAE* 

 a Larvae with wings developing externally (called nymphs in this paper) and 

 no quiescent pupal stage 

 h With biting mouth parts 

 c With long, filamentous caudal setae; labium not longer than the head, 

 and not folded on itself like a hinge 

 d Gills mainly under the thorax ; tarsal claws two ; caudal setae generally 



two (stone flies) Plecoptera 



dd Gills mainly on the sides of the abdomen ; tarsal claws single; caudal 



setae generally three ..(May flies) Ephemerida 



cc Caudal setae represented by three broad, leaf! ike respiratory plates 

 traversed by tracheae, or by small spinous appendages ; labium much 

 longer than the head when extended; at rest, folded on itself like a 

 hinge and extending between the bases of the fore legs 



(dragon flies and damsel flies) Odonata 

 hT) Mouth parts combined into a jointed beak, which is directed beneath the 



head backward between the fore legs Hemiptera 



aa Larvae proper, with wings developing internally, and invisible till the as- 

 sumption of a quiescent pupal stage 

 & With jointed thoracic legs 

 c With slender, decurved, piercing mouth parts, half as long as the body; 

 small larvae, living on fresh-water sponges. Family Hemerobiidae of 

 Neuro p tera 

 ce With biting mouth parts 

 d With a pair of prolegs on the last segment only (except in Si alls, 

 plate 29, which has a single long median tail-like process at the 

 end of the abdomen) these directed backward, and armed each with 

 one or two strong hooks or claws 

 e Abdominal segments each with a pair of long, lateral filaments 



Family Sialidae of N e u r o p t e r a 



ee Abdominal segments without long, muscular, lateral filaments, often 



with minute gill filaments ; cylindric larvae, generally living in 



portable cases (caddis flies) Trichoptera 



IThe Thysanura, or sprlngtails, common on the surface of water, but not living In it are not in. 

 eluded in this table. They will be readily recognizable, If collected, by their very minute size, 

 entire absence of wings, mouth parts retracted within the head, and the forked spring beneatli the 

 abdomen. 



