190 Mr. F. Walker's Characters of undescribed Diptera 



XVI. Characters of undescribed Diptera in the Collection 

 of W. W. Saunders, Esq., F.R.S., &;c. By Francis 

 Walker, Esq., F.L S., &c. — {Continued.) 



[Read 2nd February, 1857.] 



Fam. 16. MUSCID^. 



Div. 1. CALYPTERiE. 



Siib-fam. 1. Myopides. 

 Species few in number. 



SYNOPSIS. 



* Proboscis bigeniculata. 



-j- Antennarum articulus 2"^ 3° longior. Mijopa, Latr. 

 -j- f Antennarum articulus 2"' 3''paullo brevior. 



J Arista basalis. Dalmannia, Desv. ; Stachynia, Macq. 

 J ;J; Arista subapicalis. Stylogaster,y[ac(\. 

 Proboscis basi geniculata. Zodion, Fabr. 



« * 



Sub- fam. 2. Tachinides. 



The study of tbis family is very difficult, owing to the abund- 

 ance of species which it contains, and to the variety of characters 

 by which they are distinguished. The number of species may be 

 estimated at about 10,000, of which 1,000 are European. Spe- 

 cific descriptions of them are insufficient when they do not men- 

 tion all the parts of the structure which are subject to variation, 

 such as the following : The setae, and especially those of the 

 head ; the frontalia ; the face, whether inclined or vertical ; the 

 eyes; the antennae ; the form of the abdomen; the veins of the 

 wings, and especially the prsebrachial vein. The species are all 

 parasitic on other insects, and almost every species has its pecu- 

 liar prey, and has a corresponding variation in structure, and 

 especially in the form of the antennae. The length of the second 

 joint of these organs should always be noticed, and the form of 

 the third joint, which varies according to the sex, and accordino- 

 as the habit of the species varies, being the means which directs 



