STUDY OF VARIATION IN THE RACES OF ZYGAENA FILIPENDULAE, L. 145 



An Essay on the Systematic Study of Variation in the Races of 

 Zygaena filipendulae, L, and of its subspecies stoechadis, Brkh. 



By ROGER VERITY, M.D. 

 (Continued from p. 129.) 



Analytic remarks on the patterns of hindwing. 



The most difficult forms to study and classify systematically are 

 those which lead up from medicat/iuis, as figured by Hiibner and by 

 Boisduval, to stoechadis, as described by Borkhausen ; they include all 

 those varied and beautifully complex ones in which the dark pattern 

 gradually encroaches on the red of the basal part of the hindwing, the 

 two intermingling in different proportions. To follow this process we 

 will have to go into very minute details, but it is well worth it, because 

 they show the exact similarity of pattern on forewings and hindwings, 

 which might seem incredible at first sight, and they reveal to us the 

 origin of the somewhat fixed aspect of the former, affording thus also 

 the clue to its homology with other genera of Lepidoptera, from all of 

 which it seems in a way to stand apart. The latter subject, however, 

 I will have to leave for another paper. 



Let us begin by noting that the pattern in question is in no way of 

 nervural origin, as might be thought by the radiated look of some 

 individuals. The terminal branches of the neuration are, often 

 enough, covered by black scales, which look like capillary streaks 

 emerging from the inner outline of the marginal band, but this scaling 

 does not develop any further. Tbese may very possibly be remnants 

 of the " nervural pattern." Such, on the contrary, is not the case with 

 the much more conspicuous streaks or rays which are to be seen at the 

 back of the cell, between it and the dorsal margin. At a first glance 

 they might seem situated on the anal nervures, but a closer inspection 

 shows that they originate on the crease of the wing existing in the 

 internervural space ; the creases are so much more conspicuous than 

 the nervures that they might easily be mistaken for them. The 

 streaks usually also give the impression of being simply projections, 

 very long and sharp, of the inner outline of the marginal band 

 stretching towards or to the base of the wmg. This again is wrong : 

 they rise from centres quite distinct ; the proof of it is that in 

 some individuals the streak placed just behind the cubital 

 nervure may be seen to be separated from the marginal band by a 

 small red space or by a minute red spot situated near the root of the 

 second branch of that nervure ; it will be noticed that this is exactly 

 the position of spot N. 4 of forewing, and that the spot described 

 on hindwing is nothing else but its homologue; we thus also come to 

 the conclusion that the streaksin question are homologous with the band 

 of forewing which separates spot N. 2 from N. 4. Very often they 

 blend together in a very large triangular patch, extending behind the 

 cell, from the marginal band to the base of wing. Bocci has 

 discovered at Genoa a form of the female in which this triangle 

 is fully developed, reaching the base of the wing, and stands out on 

 an otherwise completely red hindwing, except for the marginal band, 

 not much broader than in ocfisenheimeri ; he has called it form zonata 

 (I.e., 1914). I have never seen it from any other locality. As a rule 

 the triangle only reaches a similar extent when the marginal band is 

 September, 1921. 



