THE STUDY OF INSECTS. 



The larvae are parasitic, infesting hymenopterous and 

 lepidopterous larvae and pupae and the egg-sacs of Orthop- 

 tera, The pupae are free. 



FIG. 564. Wing of Pa.nta.rbes capita. 



The family is a large one, including many genera and 

 species. 



Family THEREVID^: (The-rev'i-dae). 

 The Stiletto-flies. 



With the flies of this family the head is transverse, being 

 nearly as wide as the thorax ; and the abdomen is long and 

 tapering, suggesting the name stiletto-flies. These flies are 

 small or of medium size ; they are hairy or bristly. The 

 antennae are three-jointed ; the third segment is simple, and 

 usually bears a terminal style ; but this is sometimes want- 

 ing. Three ocelli are present. The legs are slender and 

 bristly; the empodia are wanting. 



Vein III of the wings (Fig. 565) is four-branched, and 

 the last branch (vein II I 5 ) terminates beyond the apex of 

 the wing ; the branches of vein V are all separate ; cell VIII 

 is closed near the border of the wing; the 2d cell III and 

 cell V are long. 



The adult flies are predaceous ; and conceal themselves 

 among the leaves of low bushes or settle on the ground in 

 sandy spots, waiting for other insects upon which they 

 prey. 



The larvae are long and slender, and the body is appar- 

 ently composed of nineteen segments. They are found in 



