6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



Pupae. — The stratiomyid pupa, surprisingly, is much smaller than 

 the puparium, often being only one-third the total length of the 

 latter. 



At the onset of pupation the mature larva becomes rigid, the 

 integument hardens, and the apical segments are usally in a distorted 

 position. The pupa itself, enclosed in a silky cocoon secreted by 

 the salivary glands, occupies only the anterior end of the puparium. 

 Miall (1895) reports that earlier workers often mistook the pupa for 

 a parasite that had devoured the larva. 



Because of the shrinkage of the pupa, an air space is formed within 

 the puparium, and thus the aquatic pupal stage becomes buoyant. 

 As a result, the pupa floats on the surface of ponds or other bodies 

 of water until eventually it is either blown by the wind or carried 

 by the action of waves to the shore, where it remains with other 

 debris until the adult emerges. 



At the time of emergence the puparium splits not only along the 

 dorsomedian line to the second abdominal segment, in the manner of 

 the Nematocera, but also transversely on the second abdominal 

 segment in the manner of the Cyclorrhapha. 



Adults. — Malloch (1917) and Johannsen (1935) have stated that 

 adult stratiomyids, of both terrestrial and aquatic forms, may be 

 seen flying about in areas where species of Umbelliferae and Com- 

 positae are in flower or resting on vegetation that is close to water. 

 Although there is relatively little information on feeding habits of 

 the adults, the regularity with which they are seen on vegetation 

 correlates with Lundbeck's observation (1907) that the adults feed 

 on "plant juices" (nectar?). 



The more commonly seen adults that represent species of Stratiomys 

 and Odontomyia are robust in appearance and are good fliers, but there 

 are many species in other genera that lack one or both of these at- 

 tributes. Other species, especially in the genus Sargus, are able to 

 hover about vegetation in the manner of a syrphid fly. 



Adults may be collected by sweeping in grassy meadows, in bog 

 areas, and in sedges, cattails, and other vegetation along the margins 

 of streams, lakes, and ponds. 



Predators and parasites. — Several investigators have observed 

 parasites and/or predators attacking larvae of Stratiomyidae. In 

 table 2, I have presented this information in condensed form and 

 have added my own observations. 



Morphology 



Several notable investigations on the morphology of the Stratio- 

 myidae have been made and have been concerned with the nervous 

 system, the respuatory system, the head capsule, and the integument. 



