LEONARD HASEMAN. 329 



feeding habits similar to mosquito larvae, the advantage is less 

 apparent. While feeding near the surface the tip of the abdomen 

 is protruded above the water, while the head hangs down or is bent 

 around so as to feed on floating vegetable matter. The larvae are 

 never particular about keeping the nipples above water, and bub- 

 bles of gas are not seen to come off from them as from the anal 

 spiracles. If these nipples really have spiracles they are unprotected 

 and certainly of little importance as compared with the anal spira- 

 cles, but the writer thinks that, in this species, they are simply the 

 rudiments of the prothoracic tubes of the pupa and not used for 

 respiration in the larva. 



After carefully examining a great number, both of living and 

 preserved specimens, the writer is led to conclude that there are no 

 true anal tracheal gills. Several were examined under the high 

 power of the microscope, and although a series of low papillae were 

 seen to surround the anal o[)ening, no tracheae were found in them, 

 nor were retracted gills present. In order to verify the conclusions 

 reached by the microscopical examination, the following experiment 

 was performed : 



Three larvae, one very young, one half grown, and the third 

 almost full grown, were submerged in a vessel of water under a 

 small rubber ring to which a glass cover had been cemented. There 

 was perfect communication between their little apartment and the 

 surrounding water, and they were given an abundance of food. 

 They were placed under the cover on the morning of February 9th, 

 and on examining in the evening were found to be still alive, but on 

 the following morning were all dead. They were examined from 

 time to time during the experiment, and it was noted that the anal 

 papillae became enlarged and protruded somewhat from the body. 

 It is very px'obable that these papillae are more strongly developed 

 and possess true tracheae in some Psychodids, as described and 

 figured by Muller for the Brazilian form, but the traclieae are cer- 

 tainly absent in this species. 



Concluding from this experiment and from the microscopical ex- 

 amination the writer is led to infer that in the larval stage of this 

 species respiration is carried on principally through the system of 

 tracheae, which have their external openings at the posterior end of 

 the body and possibly in the thoracic air nipples. Although the 

 experiment would seem to suggest that some oxygen is received 

 from the water, it is evident that this supply is far too inadequate 



TKANS. AM. ENT. SOC. XXXIII. (42) NOV EMBEE, 1907. 



