362 



tubes; but the species which I, have had in this stage invariably pre- 

 ferred to remain under whatever debris there was in the glass, only 

 occasionally leaving its shelter for a short time. The food is recorded 

 as consisting of crustaceans, which have been observed active in the 

 alimentary canal, and Johannsen states that "blood-worms are greedily 

 devoured by T any pus larvce."* I have not seen the larvae feed upon 

 anything but decaying vegetable matter in the debris placed in the 

 glasses I kept them in, though possibly that contained minute organ- 

 isms, and I have not attempted to confirm Johannsen's statement re- 

 garding their eating Chironomus larvae, or blood-worms. 



Larval Characters 



The head in larvae of practically all the species of this sub- 

 family is distinctly elongated, slightly narrowed anteriorly and flat- 

 tened, generally presenting in lateral aspect a slightly wedge-shaped 

 appearance. The antennae are entirely retractile within the head ; the 

 basal joint is usually very long, greatly exceeding one-half of the 

 entire length of the antenna (PI. XXIV, Figs. 2, 3. 8, 13, 15). The 

 labrum (PI. XXV, Fig. 12) is very different in structure from that 

 of the Chironomincc as there are no appendages on its under surface 

 such as are invariably found in the members of that subfamily. The 

 mandibles are much simpler than in ChironomincF, the teeth consisting 

 of a slight and rather abrupt dilatation slightly before the middle, the 

 apical margin of which is generally excised, forming two slight api- 

 cally directed teeth (PI. XXIV, Figs. 17, 18). The maxillary palpi are 

 much more slender and elongated than in Chirononiincc (see PI. 

 XXIV, Figs. 4, 6, 9, 10, 12). The labial plate is very characteristic in 

 TanypincE, and is generally retracted in preserved specimens, occupy- 

 ing an almost vertical position or occasionally turned backward so 

 that its anterior margin may be seen through the w^all of the head. 

 The structure of the labium and its appendages (PI. XXV, Figs, 

 i-ii), and the hypopharynx (PI. XXVI, Fig. 3) are as shown in 

 figures indicated. In young larvae the thoracic segments are but 

 slightly differentiated from the abdominal segments, but as the larva 

 approaches maturity the former segments expand considerably, which, 

 taken in conjunction with the long anal appendages and the rather 

 tapering abdomen, gives the larva a culicid-like appearance. The an- 

 terior pseudopods are generally long and slender in Tanypns, though 

 as the larva becomes more mature and the thoracic segments expand 

 more these are gradually reduced in size and finally almost disappear. 



*Aquatic Nematocerous Diptera, Bull. 86, N. Y. State Mus., p. 123. 1905. 



