June, I9 o S .J K.NAB : INHABITANT OF SARRACENIA PURPUREA. 71 



emerge. When the imago is about to emerge the pupa wriggles to the 

 surface of the gelatinous case. The fly is disclosed within two or three 

 days after pupation. 



The writer has found an account of one other species of Chironomi- 

 dae which pupates within a gelatinous case, but under widely different 

 conditions. It is the European Chironomus minutus Zett. , of which 

 the early stages are made known by T. H. Taylor in Miall and Ham- 

 mond's "The Harlequin Fly," p. n-13. The larva of this insect 

 pupates within a gelatinous case attached to a submerged stone in a 

 stream. The case is perforated by a passage occupied by the pupa and 

 by constant undulations of the pupal body a current of water is kept 

 flowing through the case. 



On the other hand, the larva of our Metriocnemus forms its gelat- 

 inous case above the surface of the water, and there is no passage 

 through the gelatine, but the pupa hangs imbedded in the mass. The 

 pupa, unless disturbed, remains motionless until the time of emer- 

 gence. The pupa is remarkable also in the entire absence of breath- 

 ing organs, usually present in chironomid pupae either in the form oi 

 " trumpets " or as tufts of filaments. In the pupa of the above-men- 

 tioned Chironomus minutus the respiratory trumpets are present, but 

 are extremely small. O. A. Johannsen, in "Aquatic Insects in New 

 York State," has described the pupa; of two species of Chironomidae, 

 which apparently are also without breathing organs. The pupa of 

 Diamesa wait Hi Meigen is stated to be destitute of the thoracic respi- 

 ratory appendages, but it is suggested that the three pairs of short 

 hollow filaments at the tip of the last segment may have a respiratory 

 function. In the description of the pupa of Thalassomyia obscura 

 (Johan.) no mention is made of respiratory organs, and from the ac- 

 companying figure it is to be inferred that they are absent. While no 

 direct statement is made of the pupal habitat of these two species, it 

 appears that pupation takes place within the case previously occupied 

 by the larva. 



Metriocnemus knabi appears to have a wide distribution and its range 

 is probably limited only by that of its host-plant. In addition to the 

 locality first mentioned, a bog at Wilbraham, Mass., in which Sarra- 

 cenia purpurea flourishes, furnished me both larvae and purpae on Au- 

 gust 28, 1903. Early in the spring of 1904, Dr. Geo. Dimmock 

 collected numerous larvae of various sizes near Springfield, Mass. The 

 larvae, with those of Wyeomyia smit/iii, were found in the frozen con- 

 tents of the pitcher plant leaves. Some of these larvae, under the 



