Hybridising T. listortata and T. crepuscularia. 23 
crossing = 1°64 per cent. I]I.—Percentage of the suffused 
form resembling Scotch 7. bistortata: (1) In 1st crossing 
= 19 per cent.; (2) In 2nd crossing 3°83 per cent. I[V.—The 
crossing in which 7’. bistortata was the male parent has 
produced by far the larger and more vigorous-looking 
offspring. 
Ill. Hybrids between 2 T. bistortata (Clevedon) and 2 T. 
erepuscularia (York).—No. 3 above. Two batches of eggs ; 
hatched April 25th-27th; larve fed up together; 121 
imagines examined, emerged between June 17th and 
November 38rd, 1897. These may be grouped as follows :— 
lf 429 These are pale specimens, resembling the 
second brood of 7’. bistortata in their small size, 
but distinctly of a cleaner white, thus approach- 
ing the ground-colour of 7’. crepuscularia, and 
with the fine median transverse shade or line, 
between the elbowed and basal lines (observable 
in the York 7. crepuscularia, but practically 
obsolete in the Clevedon 7’. bistortata). They 
also show a tendency to form, by means of 
darker shading outside the elbowed line and 
within the basal line, transverse bands. 
61f 92 These, the bulk of the specimens, have the 
ground-colour much suffused with fuscous 
and the transverse lines and shades distinct, 
resembling closely the Perthshire 7’ bistortata; 
the earlier emerged specimens of this form are 
smaller and lighter, the later larger and 
darker. 
a be These closely resemble small specimens of 
the early brood of 7. bistortata, although one 
sees none like them in nature. They are 
as strongly marked as the last, but suffused 
deeply with ochreous instead of fuscous. 
65 f 562 Two emerged October 31st and November 
3rd. Complete brood ; no pupz going over. 
IV. Hybrid between § T. crepuscularia (York) x 9 T. bis- 
tortata (Clevedon).—No. 4 above. Two batches of eggs ; 
hatched April 21st-28rd; larve fed up _ together; 
40 imagines examined; emerged between June 16th 
