132 Orthorrhapha brachycera. 



Geographical distribution: — Northern and middle Europe down 

 into France: towards tlie north to southern Scandinavia. 



POLYTOMA. 



Therevidae. 



Head about as broad as thorax, broader than iiigh, slightly arched 

 behind; it is somewhat flattened in front below, the face looking 

 somewhat downwards. Epistoma short, retreating; frons and epistoma 

 sometimes protruding. Jowls small, broader or narrower, slightly 

 descending below the eyes. Antennæ inserted near to each other, 

 about in the middle; they consist of four to five joints, the first joint 

 long, cylindrical, sometimes large and thickened, the second joint short, 

 the third long, the two last forming a short style terminating in a 

 small bristle (in Xestomyza the style is one-jointed). ^ Eyes touching 

 in the male, well separated (more or less) in the female. In the male 

 the upper facets are somewhat larger than the lower, the dividing 

 line more or less sharp, The eyes are generally greenish or bright 

 green, somewhat metallic; in some cases {Xestomyza, Th. poecilopa) 

 they show a purplish line. Three ocelli present. Weaker or stronger 

 occipito-orbital bristles along the posterior eye-margin. No distinct 

 oral cone. Glypeus more or less horseshoe-shaped, lying about hori- 

 zontally from the epistoma to the labrum. Proboscis short (in Xesto- 

 myza the proboscis is elongated, as long as or longer than the head). 

 Labrum, maxillæ and hypopharynx of equal length, about half as long 

 as the proboscis; labrum and hypopharynx truncate at the end; the 

 maxillæ thin, pointed, the maxillary palpi rather long, one-jointed; 

 labium with a short basal part and large, somewhat broad labella. 

 Thorax almost rectangular, longer than broad; of macrochætæ strong 

 notopleural, supraalar and postalar bristles are present, further one 

 or two dorsocentral bristles and fmally scutellar marginal bristles. 



Mik says (Verh. zool. bot. Gesell. Wien, XXXI, 1882, 329) that the antennæ of 

 Thereva are four-jointed (the style not considered); he continues: "man wird 

 auch bei jenen Formen, bei welchen das kurze dritte Glied mit dem langen 

 viertem Gliede innig verwachsen ist, eine Abgrenzung desselben wahrnehmen 

 konnen." It is thus the basal part of the third joint he considers as a separate 

 joint, but I have never found the basal part separated, and Wandellock (Zool. 

 Jahrb. VIII, 784, Tab. 18, Fig. 30) also considers the third joint as undivided. 



