895.] 255 



OCCURRENCE IN EAST ANGLIA OF MESOPHYLAX ASPERSUS, 

 Rbe., a caddis-fly NEW TO BRITAIN. 



BY ROBERT McLACIILAN, F.R.S., &c. 



In a box o£ Trichoptera sent to rae for determination by Mr. 

 Claude Morley, F.E.S., of Ipswich, I find one ? example of what 

 appears to be undoubtedly this species, taken by him on April 23rd, 

 1895, at an electric light in that town. It is of large size (expanse, 

 37 mm.). 



A description of M aspersus (as Slenophylax asprrsus) is to be 

 found in my "Revision and Synopsis," p. 132 ; and it was subsequently 

 noticed in the First Add. Suppl., p. 10 (1881;), where also certain pale 

 forms originally considered varieties are given specific rank under 

 the name M. impunctatus, McLach. It is there noticed also that a 

 single example of this latter had occurred in Dunifriesshire, and still 

 later a form, that may possibly prove to be a distinct species, dis- 

 covered in Unst, Shetland, was described by me as M. impunctatus, 

 var. zetla'idicus (Ent. Mo. Mag., xxi, p. 154 ; cf. also King, I. c, 2nd 

 series, vol. i, p. 178). Apart from its Scottish distribution, M. im- 

 punctatus is decidedly more northern than M. aspersus, which latter 

 may be said to be Mediterranean, and, like some of its allies, mostly 

 found in caves, apparently quite irrespective of hibernation, for 

 I have myself taken it in a cave in the Eastern Pyrenees in July. 

 There can, however, be little doubt that the species hibernates, and I 

 think it probable (from the date) that Mr Morley's example had done 

 so ; it is also certain that these insects are strictly nocturnal, and 

 probably fly long distances at night. 



As to the occurrence of M. aspersus at Ipswich. It may have 

 been bred in East Anglia, but this I think hardly probable It may 

 have been one of those sporadic instances of natural introduction, 

 the accounting for which is one of the most difficult problems in 

 geographical distribution. It may have been brought up the Orwell 

 in a vessel trading to the south of Europe, and in connection witli 

 this it occurs to me that the hold of a vessel might be likened to a 

 floating cave. 



Finally it should be remarked that it would have been more 

 satisfactory had the insect been a (J, and it may be that Mr. Morley, 

 or some one else, can procure an English (^ , but I confess it will be 

 an agreeable surprise to me should such an event happen. 



Lewisliani, London : 



October 9th, 1895. 



