OF WASHINGTON, VOLUME XIII, l!ll. 35 



The escape from the pupa of the mosquitoes of the genus 

 Mansonia has apparently never been observed, but it must occur 

 in a manner similar to Simuliuin. The pupa of Mansunia lives 

 submerged, attached to the roots of aquatic plants by its thor- 

 acic respiratory appendages and by their means extracting its 

 supply of air from the plant, it would seem that the pupa 

 does not even rise to the surface to free the imago, for the 

 pupal exuvia? are not found floating on the surface in swamps 

 where the larvae abound. 



According to the observations of Comstock'and Kellogg 2 

 the emergence of the Blepharoceridae from their submerged 

 pupas is a far more imperfect process and indicates the 

 primitive condition of the group. Similarly to the Simu- 

 liidae, the pupa? are attached to the rocks in swiftly flowing 

 streams. It would seem that the images only succeed in mak- 

 ing their escape when the water is very shallow (from one- 

 fourth to one-half inch in depth), and Comstock states that 

 in the deeper water they are swept away by the current. He 

 states that the fly forces its way out slowly, requiring from 

 three to five minutes to free itself, and that its body is held 

 vertically in spite of the swift current. This last fact points 

 to the rigidity of an air-inflated condition. Kellogg states 

 that he "has often watched the emergence of adults, and has 

 been struck by the great loss (apparently) of life in the pro- 

 cess. So many are swept away by the swift water before the 

 wings can be unfolded or before the legs can be loosened from 

 the pupal sheath that it seems no wonder that the family is a 

 disappearing one. It is a case of the dangers of an extreme 

 specialization. If the fixed pupae lie in water too deep (easily 

 occasioned by a sudden rise in the stream at the time for 

 emergence), or, on the other hand, become wholly bereft of 

 the life-giving water by a falling of the stream, there is no 

 hope for the fly. The first contingency seems indeed to be 

 somewhat provided for (as explained in the account, poslca, 

 of the life-history of the flies) by the apparent power of the 

 insect of postponing for some time, if necessary, its emer- 

 gence. Thus, in the event of a heavy rain and consequent 

 rise of the stream, the too deeply submerged pupa may lie 

 unchanged until the water has run off (a matter which hap- 

 pens speedily in swift streams) to a safe shallowness." 



More careful observations on the emergence of these re- 

 markable flies would be well worth while. Thus the ques- 

 tion whether the flies that are swept away by the current are 



'A manual for the study of insects, 1895, pp. 435-436. 



2 Proc. Cal. Acad. Sci., 3d Ser., Zool., vol. 3, pp. 213-215 (1903). 



