485 



ration from those of Chiroiioimts and allied genera, and in this paper 

 I have included all of them in a single key. Some, probably not all 

 of them, construct cases (see PI. XXXII, Fig. 5), but while this 

 fact is of considerable biological significance, it is obviously value- 

 less as a character for systematic arrangement unless the case is pre- 

 served along with the larva. 



The pup?e of such species as are known to the writer have elon- 

 gate unbranchcd thoracic respiratory organs and the abdominal seg- 

 ments with conspicuous groups of setulse on the dorsum. 



The imagines are distinguished from Chironomus by the presence 

 oi hairs on the wings, and from other genera in Chironomincc by the 

 elongated basal joint of the fore tarsi, which is longer than the fore 

 tibiae. The structure of the hypopygium is not unlike that of most 

 species in Chironouius but cjuite distinct from that of Cricotopus, 

 Ortliodadiiis. and Metriocncmus. In Tanytarsiis and Orthocladms 

 the third vein usually ends appreciably farther from apex of wing 

 than does the fourth, while in Chironomus these veins end respec- 

 tively at about equal distances before and behind the apex. Only in 

 a verv few species in Chironomus is there a departure from this rule, 

 but these exceptions are sufficient to cause me to refrain from re- 

 garding this character in Tanytarsus as being of generic value. 



Key to Species in Laboratory Collection 



1. Males 2 



— Females 16 



2. Fore tarsi with long hairs 3 



— Fore tarsi without long hairs, those that are present barely longer 



than the diameter of the tarsal joints 4 



3. Basal joint of fore tarsi about one seventh longer than fore tibige 



(40: 35) ; black species, legs fuscous; hypopygium as in Figure 2, 

 Plate XXXVI 1. nigripiliis. 



— Basal joint of fore tarsi nearly one half longer than tibiffi (63 : 44) ; 



legs pale brown ; hypopygium as in Figure 6, Plate XXXVI .... 

 2. dives. 



4. Basal joint of fore tarsi at least twice as long as fore tibiae 5 



— Basal joint of fore tarsi at most slightly more than half as long 



again as fore tihias 9 



5. Basal joint of fore tarsi about two and a half times as long as fore 



tibia (24 : 63) 6 



— Basal joint of fore tarsi about twice as long as fore tibia 8 



6. Second joint of fore tarsi very slightly longer than fore tibiae (25: 



24) 3. neoflavellus. 



— Second joint of fore tarsi at least one fourth longer than fore 



tibiae 7 



