DIPTEKA OK TEUE FLIES. 



229 



Winter-gnats (Tbichocera iiiemalis and T. regelationis). 



These delicate little Tipnlidse (fig. 125) are found dancing in 

 the air in clouds in the winter months whenever the weather is 

 warm. They are brownish-grey, with four brown stripes on the 

 thorax, T. hiemalis having spotless wings, while T. regelationisi 

 has a dark spot on each wing at the cross veins. The larvte 

 live in rotting turnips ; they are cylindrical, and taper to a 



Fia. 125. — Winter Gnats (Trwhowra). 

 1, 2, Larva of T. Iiiemalis j 3, 4, pupa ; 5, 6, imagines ; 7, nat. size. 



point at the head end, about half an inch long, and dirty 

 greyish-yellow in colour. They need no further comment, 

 except that they may be generally looked upon as useful 

 insects, helping the speedy decay of roots, &o., in the soil. 

 Now and again, however, they have been known to attack 

 sound plant tissue. 



Amongst the Brachycera are some of great importance : only 

 one group can be mentioned here, namely, the 



Gad-flies or Tabanidee. 



Gad-flies are large flies with a flattened body and largo broad 

 head closely united to the thorax (fig. 127, o). They are all 



