NO. 3569 SOLDIER FLY LARVAE — McFADDEN 9 



Nemotelus, however, the spu-acular chamber is located on the dorsum 

 of this segment. 



A few aquatic genera, notably Euparyphus and Odontomyia, possess 

 strongly curved sclerotized hooks or spines, as they sometimes are 

 called (fig. 122). They are usually on the venter of the seventh ab- 

 dominal segment, but in the genus Hedriodiscus they are on the venter 

 of the sixth segment as well. A remarkable feature of the sprues is 

 that they curve forward toward the head. This arrangement would 

 seem to present some difficulty in forward movement, but this has 

 not been observed. Previous workers (Wesenberg-Lmid, 1943; Lenz, 

 1923) have reported that the hooks serve as anchoi-s to keep the larvae 

 from being swept away by fast-flowing currents. This statement may 

 be partially correct, but I have observed this type of larva in shallow 

 pools that had only convection currents. 



Digestive system.- — ^The digestive system has little to offer in the 

 way of taxonomic characters other than the characteristic shape of 

 the gut, which is long and highly convoluted. Except for the mortar 

 and pestle, there are no sclerotized areas present in either the foregut 

 or the hindgut. 



Malpighian tubules. — The malpighian tubules are filled with a 

 whitish, semiliquid material that is reported to be primarily composed 

 of calcium carbonate. This material may be associated in some 

 manner with the calcium carbonate that is secreted in the integument. 



Respiratory system. — Stratiomyid larvae have frequently been 

 described as peripneustic, but it is doubtful that they are fimctionally 

 so. They appear to be metapneustic or in some cases amphipneustic. 

 The lateral spiracles almost always are minute and difficult to detect, 

 especially in the later instars. The only spiracles that fimction con- 

 tinually are the terminal or posterior spiracles. 



The spiracular chamber contains the ends of the main tracheal 

 trunks. In the aquatic forms, the lips that form the opening to the 

 chamber are fringed wdth long hydrofuge setae, which enable the 

 larvae to remain suspended from the surface of water for indefinite 

 periods of time while the spu-acles are open to the atmosphere. When 

 submerged, these setae also aid respiration by enclosing an air bubble 

 trapped m the process of submerging. 



Using the work of Whitten (1959) as a guide, I examined the tracheal 

 system of 4 genera (2 aquatic and 2 terrestrial) for possible taxonomic 

 characters. The tracheal system of each larva has the same general 

 pattern as that given by Whitten for brachycerous larvae and, con- 

 sequently, cannot be used as a distinguishing character beyond the 

 suborder. 



Nervous system. — -Although several studies have been made on 

 the nervous system of a few species of stratiomyid larvae, the results 



