THE TRIBE ATHERICERA. 91 



The species are exceedingly numerous, and they are found in most parts of the world. Over 

 200 are recorded as inhabiting Europe, and a large proportion of these occur in Britain. A great 

 many have also been described as inhabitants of the United States, but the known species from 

 tropical and southern regions are comparatively few, so that as far as present knowledge goes the 

 family would seem to abound particularly in the temperate and colder parts of the northern hemi 

 sphei-e. Many species are found high up on mountains. 



FAMILY XVII. PLATYPEZID^E. 



The Platypezidae are a very small family of minute Diptera, nearly related to the Dolichopodidse, 

 but differing from them in the flattened form of the body, the hemispherical shape of the head, which 

 in the males is almost entirely occupied by the eyes, the shortness of the legs, of which the posterior 

 pair are stout, and the presence of six instead of five longitudinal veins in the wings. The number of 

 species is small, and very few are recorded from beyond the European region. Most of the genera are 

 represented in Britain. 



The perfect insects, most of which are under one-sixth of an inch in length, are active in 

 their habits, and are generally found in woods and about hedges, although some of them prefer 

 the herbage of marshy localities. Their larvae live in fungi, and are broad and rather flattened, 

 with stiff bristles along their margins. These insects, like the preceding, seem to lead towards 

 the next tribe. 



FAMILY XVIII. -SCENOPINLTXE. 



A few very small flies, which seem to have some affinity to the Thereviclae, have been formed into 

 a separate family under the above name. They have short antennae, with three joints, of which the 

 third is the longest, blunt at the tip, and without any bristle ; a very short, fleshy proboscis, termi- 

 nated by broad lobes, but with only a single enclosed bristle ; short legs ; and wings with a complete 

 cell on the disc. These insects also lead in the direction of the next tribe, but their long slender larvae, 

 which live in fungi, cast their skin on passing to the pupa state, and in other characters, such as 

 the venation of the wings, they rather resemble the central types of the Tanystorna. Scenopinus 

 fenestralis, a small fly rather more than a sixth of an inch long, receives its specific name from its 

 being common on windows, especially those of stables ; it is also found on the leaves of plants 

 and about walls. It is black, with reddish tawny legs. Another common species in similar 

 situations (S. fasciatus) is entirely black except the tarsi, which are reddish. 



TRIBE IV. ATHERICERA. 



As already indicated, some families of the preceding tribe show an evident transition towards 

 the present one, but in all cases the character of the metamorphosis serves to tura. the scale. In 

 all the Tanystoma the larva skin is cast when the insect passes into the pupa state ; in all the 

 Athericera the transformation takes place within the skin of the larva, which hardens into an oval case, 

 serving efficiently as a protection to the helpless inmate. The antennae throughout the tribe consist 

 of only two or three joints, of which the third is never ringed, but generally furnished with a style 

 or bristle, which may spring either from its extremity or from its back. The proboscis is sometimes 

 quite rudimentary, but is generally a more or less fleshy or membranous organ, with very distinct 

 terminal lobes ; it is always elbowed at a short distance from its base, and in most cases can be 

 retracted within the cavity of the mouth, which is situated on the lower surface of the head. The 

 palpi, which consist of a single joint, are attached to the sides of the proboscis a little above the 

 bend, so that when the proboscis is withdrawn they are entirely concealed. In one family of 

 the tribe the proboscis encloses three lancets besides the labrum ; in the remainder only one. 



The larvae are soft, fleshy, footless grubs, distinctly segmented, nan-owed, and usually pointed in 

 front, but without anything that can be distinguished as a head. The mouth is furnished with 

 one or two hook-like organs, and usually with fleshy lobes, and with a kind of tongue. The posterior 

 end of the body generally terminates bluntly, and is in many cases cut off quite flat. Upon the surface 

 of the last segment we find a pair of stigmata, which are the sole breathing apertures of the larva. 

 In general terms, we may say that most of the larvae of this tribe are maggots. A few aquatic 

 larvae are provided with breathing tubes. 



