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V. Two new British species of Hydroptila. By Martin 

 E. MosELY, F.E.S. 



[Read February 1st, 1022.] 



Plate II. 



In a paper read before this Society in October 1919, I 

 mentioned that there were in my collection two undescribed 

 British species of Hydroptila. At the time, lack of material 

 precluded the exhaustive examination of the scent-organs 

 which now seems necessary for the satisfactory separation 

 of the four species which are grouped round and which very 

 closely resemble H. sparsa Curt. 



Last season I was successful in finding three or four 

 more examples of each of these new species, and with 

 Dr. H. Eltringham's kind assistance have ascertained that 

 the scent-organs furnish abundant characters to prove that 

 they are distinct. 



H. cornuta has no eversible filament at all, and the scent- 

 organ is reduced to the simplest form so far seen in 

 Hydroptila. It resembles sparsa in the shape of the lobe 

 and also in the marginal outline of the dorsal plate, but the 

 inferior appendages bear a closer resemblance to those of 

 siinulans. 



H. angulata closely resembles H. simulans in the shape of 

 the dorsal plate and the arrangement of the scent-organ. 

 Dr. Eltringham, however, has ascertained that the scent- 

 hairs of the brushes are much finer and apparently have no 

 external structure. A marked difference is shown in the 

 shape of the lobe or scent-organ cap. 



It may be of interest to mention here, that H. simulans 

 has been found very plentifully in Hampshire ; along some 

 stretches of the R. Test it may be said to be the prevailing 

 Hydroptila species for a considerable portion of the summer 

 and autumn. I have now obtained some hundreds of 

 examples from this district. I have also taken it on the 

 R. Avon at Ringwood, the R. Torridge at Sheepwash in 

 N. Devon, the R. Thames at Hampton Court, and Dr. Georg 

 Ulmer writes that he has found it in his collection mixed 

 with examples of sparsa from Thiiringen. 



H. angulata and H. cornuta seem comparatively rare. Of 

 angulata I have three examples from the Lambourne, in 



TRANS. ENT. SOC. LOND, 1922, — PARTS I, II. (JULY) 



