22 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 51 



Front view of head of a Muscoidean fly (half in diagram), much enlarged. 



(Original, from drawing prepared by the Bureau of Entomology.) 



The heavy black line indicates the ptilinal suture. = Ocellar plate. 

 VF = Frontalia. ~P~P — Parafrontals. PicPic : =Parafacials. CC = Cheeks. 

 EE = Compound eyes. L = Lunula (postfront of larval insects). A = Antennal 

 ridge (mesofront of larval insects). Fp Fp = Mesofacial plate (plus facialia 

 equals prefront of larval insects). Fa Fa = Facialia. (Part^ from lunula to 

 facialia both inclusive taken together constitute the homologue of the front of 

 larval insects.) TZp = Epistoma. C\ = Clypcus. PI PI = Palpi. 



EXTERNAL ANATOMICAL PARTS AND CHARACTERS 



(Head) 



1) Ptilinal suture (through which is protruded the ptilinum of Robineau- 

 Desvoidy) evenly rounded and widened above, narrowed above, subangular at 

 top; its sides parallel, divergent, convergent; its termini high or low where 

 they join the cheek grooves; position of its termini with relation to lower eye- 

 border, epistoma and vibrissal angles. 



