180 [August. 



occurs upon the wiug, but. numbers of specimens show that a sweep of 

 the net through the swarm at tirst catches nothing but males carrying 

 the objects that had been strewn on the water, while a later sweep 

 catches pairs still carrying the same objects. The specimens illus- 

 trating this investigation are all carefully labelled with the hour and 

 minute at which the different samples were secured. 



Mr. Hamm's admirable experiments also enabled him to deter- 

 mine that the females carry the objects provided by the males ; for 

 although they are never retained when the pairs are captured, the 

 white florets or the yellow stamens can be seen hanging from the low'er 

 Hilara of each flying pair, and the lower is invariably the female. 



The climax is reached in the males of certain species of Hilara 

 which envelope the prey or other minute object in a cocoon, varying 

 greatly in complexity, but in the most extreme cases of striking beauty 

 and regularity. The cocoon is spun upon the wing, so that the 

 method of its construction cannot be followed. Captured individuals 

 are often found to have extruded a viscid globule — probably the 

 material out of which the cocoon is spun. There can be little doubt 

 that in these extreme cases it is the cocoon itself which acts as a 

 stimulus to the female, although the minvite and almost invisible 

 object usually enclosed in it, but sometimes dropped, is the stimulus 

 which incites the male to spin. Cocoons that have been dropped, 

 probably after pairing, are constantly picked up and used over again 

 by other males. j 



These novel and surprising conclusions, obtained as the outcome 

 of Mr. Hamm's energy, resource, and power of accurate observation, 

 are illustrated and confirmed by an immense mass of mounted material, 

 catalogued luider 355 nimibers in 1910, and no less than 660 in IDll." 



TWO DIPTEEA (LIMNOBIIDM) NEW TO BRITAIN. 



BY A. E. J. CARTER. 



1. DlCRANOMYIA RUFIVENTBIS, Strobl. 



This species is closely allied to Dicranomyia morio, Fabr. It was 

 described as a variety of that species by Strobl in 1900 under the 

 name of var. rufiventris, differing from typical morio in having the 

 abdomen, genitalia, and legs " einfarbig rotgelb," and the wings not 

 grey, but light brownish tinged with a very pale stigma. 



A male in my collection, taken at Aberfoyle, Perthshire, on 

 August 21st, 1906, has always been a puzzle. It runs down with 



