1890.] 99 



former, it is almost impossible to emi^loy language which is equally 

 applicable to every variety, and it must be self-evident that the 

 differences pointed out become intensified or modified as the opposite 

 extremes of variation are approached. In every instance, however, 

 I believe that several of the points will be found to hold good, and 

 will, I hope, lead to a correct conclusion, even in the determination of 

 the few individuals which may at first sight appear to be intermediate 

 between these species. I should very much like to see the Irish 

 specimens mentioned by Mr. Briggs as being equally referable to either 

 species. To any one who has once become thoroughly familiar with 

 the appearance of craicegeUa, when in fine condition, it must surely 

 seem almost beyond dispute that it is an '•abundantly distinct" species, 

 and by far the quickest and easiest way of separating it out of a 

 mixed series is by the eye alone, a single glance being generally quite 

 sufiicient for the purpose. 



My series of mercurella consists of some seventy specimens, 

 picked out from the many hundreds which I have taken or bred, and 

 set, of late years, and shows a marvellous range of variation from the 

 very whitest yar. 2)orfIa7idica down to the very darkest var. concinnella. 

 Cratcecjella, however, seems to be rather scarce in this part of the 

 country, and during the same period I have not captured ten specimens 

 altogether ; as it is but poorly represented in my own cabinet, I have 

 had to depend largely on the kindness of friends for the loan of 

 examples for my present purpose. In so far as I have seen it in col- 

 lections, or can ascertain, though variable, it does not present any 

 extreme varieties. It is very widely distributed ; but I remember the 

 late Mr. Sang telling me that cratcegeUa was the commoner species in 

 the north of England, whilst he believed mercurella to be the more 

 plentiful in the south ; and this is certainly the case, in so far as 

 this county, the Worthing district, and the localities worked by Mr. 

 J. W. Tutt, are concerned. 



Apart from every other consideration, cratcegeUa could not by 

 any possibility be, as suggested by Mr. Briggs, a " local chalk variety " 

 of anything, as it seems to occur on every sort of formation, and my 

 few captures have all been made on the stiffest clay ! 



After a very careful and critical examination, the following seem to 

 me to be the most trustworthy distinctions between the two species : — 



1. CratcegeUa is altogether a prettier and cleaner-looking insect, the markings 

 being much neater, and standing out more prominently owing to their not being so 

 much obscured by dark clouding. The prevailing colour of the fore-wings varies 

 from pale grey to dark grey, while in mercurella it ranges from pure spotless white 



