MYCETOPIIILIDyE. 385 



black with a white stripe on the mesonotum, the metanotum 



and flanks being white, and the legs banded with white. It is 



a Avidely diffused species, 



and presents a most sin- 



gular appearance when fly- 



ing, as it moves slowly, 



with its feet variegated Fi s- 306 - 



with snow-white, and extending like the radii of a circle. (Os- 



ten Sacken.) In the genus Protoplasma (Fig. 306, wing) there 



are six posterior cells in the wing. P. Fitchii O. Sacken is 



brownish gray, with brown bands on the wings. 



Macquart. This family comprises small 

 flies, capable of leaping to a considerable height, and provided 

 with two or three ocelli, but not having a proboscis. While 

 the antennae are usually simple, as in all other Diptera, those 

 of Platyroptilon Miersii Westwood are forked, having a 

 branch one-half as long as the antenna itself. The thorax does 

 not have a transverse suture, and the wings are without a discal 

 cell, while the coxae are greatly elongated, and the tibiae are all 

 armed with spurs. The larvae are subcylindrical and smooth, 

 with locomotive bristles beneath, and eight pairs of stig- 

 mata ; they are in color white or yellowish. They are gregari- 

 ous, living in decaying vegetable matter, fungi, or in dung, one 

 species forming a gall. They shed their skin several times be- 

 fore becoming fully grown. Osten Sacken states that the larva 

 of Sciopliila which covers the surface of the fungus it feeds in 

 with a web, is long and almost serpentiform, while those of 

 Bolilophila and Mycetopliila are shorter and stouter, and that 

 of Sciara is intermediate. The pupae of this family are 

 smooth, with rounded angles and edges, whereas those of 

 Tipula are sharp and pointed. They are enclosed in a silken 

 cocoon. Some species of Sciara do not, however, spin cocoons. 

 The larva of Mycetopliila scatophora Ferris ' ' carries on its 

 back a sheath formed of its own excrements and moulded by 

 means of a peculiar undulatory motion of the skin. The 

 pupae remain within the sheath, but before assuming this state 

 the larva extends the sheath anteriorly in a short neck, and 

 tapestries it on the inside with a pellicle, which renders it 

 25 



