260 Sciara tritici, Coq. A Fly Injurious to Seedlings 



which lias within the last few years been more or less used in the compost 

 for raising orchids from seed, or in the Sphagnum moss, which has 

 always been used since the first experiments in raising epiphytic orchids. 

 The Osmunda fern fibre comes from N. America, the Sphagnum used 

 is British." 



In the case of these orchids the possibility should not be overlooked 

 that at least some of the damage may be caused by springtails (Collem- 

 bola). These insects were present in large numbers in the contents 

 of some pots sent to the British Museum by Mr St Quintin, and it is 

 worth recalling that in 1902 Prof. F. V. Theobald recorded a case of 

 injury to seedling orchids by springtails in Surrey (vide First Report 

 on Economic Zoology, Brit. Mus. Nat. Hist., p. 110). In this last- 

 mentioned case specimens of a Sciarid fly {Zygonema sp.) were found 

 in addition to the Collembohi, but Theobald had little doubt that the 

 damage was really caused by the latter. In Mr St Quintin's pots both 

 the Collembola and the Sciara larvae were much more numerous in 

 the Osmunda compost than in the Sphagnum. 



Prof. Theobald has recently had a species of Sciara injuring tomato 

 seedlings at Wye, and at my request he kindly sent me specimens of 

 the fly concerned ; contrary to expectation they proved not to be 

 S. tritici, although they were not in sufficiently good preservation 

 to be determined accurately. 



Sciara tritici is a small fly about 2 mm. long, differing from most of 

 its congeners in the reddish coloration of the thorax, somewhat darker 

 towards the margins when viewed from above; the abdomen is rather 

 darker than the thorax. Its most obvious distinguishing feature 

 however — by which it may be separated from all the other members 

 of the genus so far described — is the possession of a whitish-yellow 

 stripe on the dark brown pleurae, connecting the bases of the front 

 and middle coxae. There is also a whitish spot below the shoulder. 

 It belongs to the group II.A.1.C.6 of Winnertz's monograph. Coquillet, 

 in the paper cited, gives a good description and figures the larva, pupa 

 and adult; from these the species will be easily recognised, but it may 

 be pointed out that the figure of the wing is not accurate, the subcostal 

 cell being made much too narrow. 



V. W. E. 



'I'm; British Mi'ski-.m ok \\tik\i, Hintoky. 

 November, 1015. 



