148 DOLICHOPID^. 



lobe, the Dolichopida differ from the former in the veining of the 

 wings, and particularly in the minute pobrachial areolet not being 

 separated from the discal. Usually also the head evidently larger 

 in proportion, the abdomen of fewer segments, the spines at the 

 end of the posterior tibiae, the different direction of the external 

 sexual organs, and . the metallic tints, assist to characterize them. 

 The Lonchopterida differ evidently by the bristly face and cheeks, 

 and the form and veining of their wings, which want the discal 

 areolet. The Platypezida have the ternate areolets (i. e., prse- 

 brachial, pobrachial, and anal) all complete, and in general a 

 rounded axillary lobe to the wings. Among the Muscida some 

 of the groups towards the end present partial resemblances to the 

 Dolichopida ; in particular the EpJiydrini, with which they were 

 originally united by Fallen ; but the porrected proboscis of these, 

 forming a visible angle with the mentum, the face expanded below 

 into the cheeks, and usually also the deflected antennae, will pre- 

 vent their being confounded with the present family. 



With respect to the internal anatomy, the Dolichopida present 

 some peculiarities so great that Dufour treats of them as excep- 

 tional cases in the Order ; concerning which, see his summary 

 in ' Annales des Sciences Naturelles/ 3 me serie, tome i. 



The Dolichopidce are all predaceous. They can run on the sur- 

 face of the water, like the Gerrida among the Hemiptera, and in 

 this manner many of them catch their prey, consisting of smaller 

 insects, Annelida, and even small conchiferous Gasteropoda. The 

 gaping orifice at the end of the proboscis, formed by the intro- 

 verted labella, admits and holds fast the prey until its juices are 

 sucked out : but the structure of the mouth seems incompatible 

 with what Fischer supposed he saw, viz., that Medeterus diadema 

 swallows its prey whole by this aperture. The groups which have 

 naked eyes (Psilopus, &c.) usually frequent dry places. 



With respect to the earlier states of these insects, we know 

 even now little more than what Degeer observed eighty years ago. 

 In the middle of the month of May he got under ground some 

 slender cylindrical larvae, of twelve segments, white and smooth, 

 pointed at the anterior extremity ; the head variable in form and 

 retractile; the mandibles appearing externally as two tubercles, 

 that meet and part, with a smaller point enclosed between them, 

 their internal continuations separate, long, and much thickened at 

 the root ; on the underside of the segments some protuberances, 

 serving as feet ; the last segment rather thicker, ending with two 

 recurved hooks, and below these two conical fleshy protuberances, 

 in which the trunks of the tracheae seem respectively to have their 



