MUSCID^, 



they are partly or wlioUy divided by the triangular interfrontalia. 

 The 23tiUmim is a soft membrane, which in many species, and espe- 

 cially in the newly-hatched flies, appears between the antennae 

 and the front, and is alternately projected and withdrawn. The 

 fades extends from the base of the antennre to the epistoma ; its 

 middle part contains two fovea, in which the antennse rest ; its 

 lateral borders are the facialia, and are frequently setigerous. 

 The mecUana are two triangular parts between the facialia and the 

 optica, or borders of the eyes, a little above the lateral borders of 

 the peristoma. The lateralla are beyond tliera, and on the lower 

 sides of the peristoma. The third joint of the antennae attains 

 its maximum of development in the leading groups of this family, 

 and may be the organ of smell; it is perforated on its inner side 

 in the larger TacJnnides. The fourth, fifth, and sixth joints form 

 the arista, or bristle ; the fourth and fifth are obsolete in most 

 genera. In the wings the flexure of the prajbrachial vein is gene- 

 rally a characteristic of the TacMnides and of the Miiscides which 

 have the most powerful flight. The radial vein springs from the 

 mediastinal vein, near the humeral transverse vein. The cubital 

 vein springs from the radial near its base, and is connected with 

 the prsebrachial before one-third of its length by a thick slightly 

 oblique transverse vein. The pobrachial vein springs like the 

 pra^brachial and the anal from the intermediate axis, near which 

 it is connected with them by two transverse veins. The distance 

 of the discal transverse vein from the border is measured on the 

 continuation of the pobrachial vein. The anal vein is almost 

 obsolete soon after its junction with the pobrachial. The subanal 

 vein springs from the intermediate axis. 



Some species are insectivorous, many are parasitic in the larva 

 state, the rest feed on living or decaying animal or vegetable 

 matter. The species will form two divisions : — 



Alulae distinct 1. CALYPTERiE. 



Alulae indistinct or none 3. Acalypter^. 



Alulce distincta.—Div. 1. CALYPTER^E. 



The Calypterce are generally also distinguished by their comparatively 

 large size, compact bodies, dark or mctaUic bodies, and fretjucntly by 

 the development of the fourth and tifth joints of the antennae or the 

 basal joints of the arista. 



Calypteratce p., et Mesomyda, Desv. CrcopJiylce et Anthomyzidfe, Latr. ; 

 Mcq. Calypterce, Meig. 



