18(52.] 165 



We have mentioned already, that tlie pupa of Sciara is sometinicH en- 

 closed in a cocoon, sonietiines not, and that, in some species, the bases of 

 the antennae are expanded into a pair of pointed teeth, and the prothoracic 

 stigmata assume the shape of horns.* 



About the habits of Platyura, Asinduhim, Plesiastina and some other 

 genera, see References at the end. Nothing is as yet known about the 

 structure of their larvae ; and it is not at all impossible that some of them 

 belong, like those of Mijcetohia (see page 1), to a totally different type of 

 organization. 



* I may be allowed to describe here a remarkable Sciara, distinguished from the 

 other species of the family by the form of the fork on the wings, and which I 

 reared from larvse and pupse found in dry cow-dung, near Washington, in April, 

 1861. 



Sciara toxoneura n. sp. — Nigra, antennis, ore, palpisque nigris, thorace nigro, 

 polito, coxis anticis flavescentibus ; alis % subhyalinis, 9 nigrescentibus; rarao 

 superiore furcse alarum valde arcuato, ventricoso; long. 0.12 — 0.15. 



Head, mouth and palpi black; antennae black, covered with a short, dense pu- 

 besence; no verticils, nor any longer hairs; joints cylindrical, connected by very 

 short pedicels ; front, vertex and thorax black, shining ; pleurse velvety black ; 

 halteres blackish; feet pale, with a blackish tinge ; a darker spot on the knees; 

 tarsi also darker; coxae pale or yellowish, basis black; tibiae with a pair of short, 

 yellow spurs at tip; abdomen black; the connecting skin between the segments, 

 when distended, especially on the last segment of the female, yellow; wings ( % ) 

 almost hyaline, ( 9 ) tinged with inky black, hyaline at base; the anterior branch 

 of the fork, being very arcuated at the basis, forms a knee; its latter half is 

 straight ; posterior branch only slightly curved ; cross-vein, connecting the first 

 and second longitudinal veins is a little anterior to the middle of the distance be- 

 tween the tip of the first longitudinal vein and the origin of the petiole of the 

 fork. 



This species somewhat resembles Zygoneura by the form of the fork, but is dis- 

 tinct on account of the structure of its antennse. 



Larva. Head black, hind margin somewhat produced and emargined in the 

 middle ; occipital lines convergent (very faint) ; on the under side it has two 

 horny stripes, connecting the edges of the horny shell ; body white, anal segment 

 somewhat coarctate in the middle. 



Pupa yellowish ; head, thorax and wings become blackish before the exclusion 

 of the perfect insect ; basis of the antennae and thoracic spiracles as mentioned 

 above (see figure 22). 



