347 



Melander have placed Arthropcas in Stratiomyiidae and Rhacicerus 

 in Xylophagidae in their recent book*, using the adult characters as 

 their criteria. 



FAMILY CHARACTERS 



Larva. — Head not retractile, the exposed portion in the form of 

 a chitinized cone, from a small apical opening in which the man- 

 dibulate portions are extruded ; several strong hairs on dorsum. Dor- 

 sum of some of the thoracic segments chitinized entirely or in part, 

 usually in the form of 3 plates; prothoraeic spiracle large. Abdominal 

 segments with locomotor spines in transverse series ; apical segment 

 obliquely truncated, the apex heavily chitinized, and with 2 backward- 

 ly projecting processes on lower margin; spiracles large, rounded, 

 widely separated, situated above middle of the chitinized plate. 

 Thoracic and abdominal segments each with a number of strong hairs. 



Pupa. — Head without thorns except sometimes one on base of 

 each antennal sheath, the latter separated from surface of head, elon- 

 gate, directed almost straight laterad, their apical portions rounded 

 in cross-section and distinctly annulated. Thorax with marginal series 

 of punctures along the sutures ; wings extending to apex of first ab- 

 dominal segment ; apices of hind tarsi extending to or very slightly 

 beyond apices of wings. Abdominal armature increasing in strength 

 from second segment to apical one, almost absent on basal ; apical seg- 

 ment ending in a bifid tubercle. 



Imago. — The species are very closely allied to those of Leptidae, 

 but may be readily separated from the latter by the structure of the 

 antennae, as indicated in the synoptic key to families of Brachycera. 



LARVAL AND IMAGINAL HABITS 



The larvae as far as known live under bark or in earth and feed 

 upon larvae of other insects. The imagines are found generally in 

 woods, and as far as I have observed feed upon nectar of flowers and 

 sap or other liquid matter. 



Xylophagus Meigen 



Keys to Species 



larvae 



1. First and second thoracic segments chitinized dorsally lug ens. 



— First, second, and a large portion of third thoracic segments chitin- 

 ized dorsally abdominalis. 



*Key to the Families of North American Insects, p. G4. (1915) 



