* MUSCID^E. 



they are partly or wholly divided by the triangular interfrontalia. 

 The ptilinum 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 and the front, and is alternately projected and withdrawn.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 antennae to the epistoma ; its 

 middle part contains two fovete, in which the antennae rest; its 

 lateral borders are the facwlm, and are frequently setigerous. 

 The mediana 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 lateralia are beyond them, 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 TacJiinides. 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 praebrachial vein is gene- 

 rally a characteristic of the Tachinides and of the Huscides 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 praebrachial before one-third of its length by a thick slightly 

 oblique transverse vein. The pobrachial vein springs like the 

 praebrachial 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. CALYPTER^E. 



Alulae indistinct or none 2. ACALYPTER^E. 



Alula distincta.Div. 1. CALYPTEILE. 



The Caly pierce are generally also distinguished by their comparatively 

 large size, compact bodies, dark or metallic bodies, and frequently by 

 the development of the fourth and fifth joints of the antenna or the 

 basal joints of the arista. 



CalypteratcB p., et Mesomyda, Desv. CreopJiylce et Anthomyzida, Latr. ; 

 Mcq. Caly pierce, Meig. 



