STUDY OF VARIATION IN THE RACES OF ZYGAENA FILIPENDULAE, L. 85 



it could only be a compound of the three. This phenomenon seemed 

 so wonderful that I very much wished to see it ; I begged M. G. 

 Foulquier to collect a large series of specimens for me in exactly the 

 same locality as Oberthiir's. When I got them I could for some time 

 make nothing more than the latter of them, but as I made progress in 

 puzzling out the difficulties in my Italian series, the truth dawned on 

 me also concerning anceps. Another difficulty, which, as he recounts 

 at length at pages 549 and 550, troubled Oberthiir very much, was 

 that of a series collected by himself and his brother at Cauterets: here 

 49 specimens were most typical lo)iicerae, 75 "could well be filipendiilae," 

 but 15 others could in no way be grouped either with the former or 

 the latter, being perfectly transitional. This is exactly the experience 

 which I went through in attempting to classify my Italian Zyyaena. 

 I had in several localities of Tuscany (Abetone, Piteglio, Covigliaio, 

 Mount Senario) collected stoechadis and lonicerae together, the second 

 beginning to emerge when the mass of the first was on the wing. I 

 had invariably found a small number of specimens, which it seemed 

 absurd to separate from the lonicerae, as they resembled it in every 

 respect, but which exhibited on the other hand some slight trace 

 (sometimes scarcely perceptible, but still unmistakeably there) of a 

 stoecltadis characteristic, such as four or five red scales on the underside 

 of the forewing in the place of the sixth spot. These extreme in- 

 dividuals were connected to stoechadis by a gradual series of intermediate 

 forms, rapidly getting more numerous as they approached the more 

 usual aspects of this insect. For some time I could not see how, with 

 such facts before me, it was possible to deny that there existed two 

 divergent series of forms, culminating in two species, but still not 

 so sterile between each other as to hinder the production of offspring 

 from cross-pairing. In short it seemed as if we had before our very 

 eyes an example of the origin of species. That was more or less the 

 conclusion reached by Oberthiir and he had to admit it, notwith- 

 standing the greatest reluctance and although, to use his words, " his 

 spirit revolted at the idea." 



Being a convinced evolutionist, I was far from having these 

 scruples, but, still I quite saw that several points in that explanation 

 were open to criticism. It was difficult to imagine, for instance, how 

 two groups of individuals, which interbred so often as to constantly 

 produce intermediate forms, could keep distinct. Querci too, on the 

 strength of his field-experience, maintained that lonicerae and 

 filipendulae must be two perfectly distinct species. We determined 

 to clear up this mystery and during the last few years we collected 

 large series of specimens in every possible locality. It was only a few 

 weeks ago, however, that the explanation made itself clear, when I was 

 struck by the fact that a few individuals of the most extreme 

 variations of stoechadis, especially in the female sex, from localities 

 where lonicerae never occurs, were so exactly similar to the latter that 

 it was in some cases impossible to distinguish them from it, and in 

 others it required consideration to do so. It then became obvious that 

 forms apparently transitional to lonicerae, in localities where the two 

 species fly together, are in reality only transitions to these extreme 

 individual variations of stoechadis, which one would unhesitatingly 

 have classified amongst the- real lonicerae and which I have named in 

 consequence lonicerae for in is (Bull. Soc. Entom. Ital., xlvii., p. 74 (Dec. 



