T. 13IST0RTATA (cREPUSCCT.ARIA) AND T. CREPUSCULARIA (bIUNDULARIa). 143 



size and superficial resemblance of our southern July brood {i.e., 

 ab. comonaria, St.)." I think Mr. Tutt is in error in referring 

 those Perth specimens to T. hisU>rtata,-\ for the following reasons : — 

 (1) The date of emergence, which is that of T. crcjiuscularia [hiiuuhi- 

 laria). The earliest dates on which this form has been noticed are 

 April 28th (Lawson), April 10th (Bush), April 28th (Wylie). Mr. 

 Lawson states the species to be in its prime from May 5th to 10th ; 

 Mr. Wylie, from May 4th to 10th. These datesj, in my opinion, 

 establish beyond a doubt the identity of the species with T. creptiscu- 

 laria. (2) I consider them to be T. orpusnilaria, because the Perth 

 insect is always single-brooded, a striking characteristic of this species, 

 and one that rarely occurs with T. hi.stortata, which is generally 

 double-brooded in the localities where it occurs. 



At my request, Messrs. Kane and Eiding have very kindly given 

 me their views as to the Perth specimens, I having previously sub- 

 mitted specimens for their examination. Mr. Kane says: — " As to 

 the Perth forms, I find myself much perplexed. The two submitted 

 agree with many of the ordinary forms of T. hi.stortata.^' Dr. Riding 

 writes : — " For those who hold, as I am inclined (from the Perth 

 specimens I have seen), that the Perth insect is T. bistortata, there 

 seems no other explanation than that the latter must have spread 

 themselves as far as Perth, where they found a suitable environment, 

 whilst those in the gap between Perth and their southern habitats 

 lost their foot-hold, owing to subsequent changes and unsuitability. 

 To my mind it is much more reasonably accounted for by considering 

 T. hiatortata to be the original stock, and the Perth forms a reversion, 

 under local conditions, from the northern T. crejmscularia, formerly a 

 variety of -Z'. bistortata, but now established as a separate species." 



Having now reviewed, although briefly, the principal points of 

 interest in the discussion carried on in the Entom., 188G, I will now 

 refer to the material collected from the 58 British lepidopterists, in 

 answer to questions which I asked, and which were printed in the 

 Entom. Record, viii., pp. 236-237. To mention all these gentlemen by 

 name would be superfluous, and the material has assumed such 

 gigantic proportions, that I can only comment upon the most 

 important points. 



The first of these refers to Mr. Arkle's belief that there are two 

 broods of T. crepuscidaria, " at least in some seasons," in Delamere 

 Forest, where, it would appear, only the ab. delaiiifreiisis occuvh. I do 

 not agree with him in thinking that the dates furnished by him, 

 vis., April 20th to June 13th, prove the existence of two broods, 

 but am convinced that they are only examples of protracted emergence. 

 Mr. Arkle's dates agree with mine for the appearance of the York 

 specimens, viz., April 4th to June 13th, and here there is certainly 



+ These are nearer to the Continental type of 2'. hixtortata than any other 

 British specimens. Our ordinary ochreous southern form = ab. ahietaria. Haw. 

 We are pleased to see that Messrs. Kane and Eiding came to, what we consider, 

 a correct conclusion on two specimens. — Ed. 



t Surely these dates suggest exactly the opposite. Mr. Young (see footnote 

 p. 108) gives " from the middle of May to June 10th," as the best time for 

 T. crepuscularia in York. Perth is 2^^' farther north, and the localities for 

 T. bistortata are distinctly Alpine. The larch woods of Kinnoull Hill and 

 Kinfaun are at a considerable elevation, and Burnham Hill (15^ miles north 

 of Perth) has an elevation of 1,324 ft. — Ep. 



