108 



THE ENTOMOLOGIST S RECORD. 



join the other band there and what, in respect of the dark pattern, can 

 be called a space, is left between them ; this is spot sixth. What I 

 wish to point out is that the atrophied zone in the Zygaena does, not 

 affect the true primary pattern or affects it extremely little. If we 

 examine Z. carniolica, Sc, in which the nervural pattern does not 

 exist, or nearly so, we find that usually the marginal band and the 

 preceding one are separated on most of their length by a long kidney- 

 shaped space or red spot ; in southern races, where this space gets 

 obliterated in some individuals by the unusual extent of the primary 

 pattern, one sees that, whilst the fusion of these bands begins at the 

 two ends of that space, at the same time the latter gets rapidly much 

 narrower, being invaded both from the innerside and the outerside, so 

 that at the end of the process there remains nothing of the space but 

 two or three minute round specks at quite a distance from spot 5th. 

 No stage is thus gone through similar to the 6th spot of filipendulae 

 elongated outwardly. If we now examine series of Z. purpuralis, Brii., 

 where the nervular pattern exists alone, we can on the contrary notice 

 that, when the marginal band broadens, in many individuals it does 

 not do so uniformly on all its length, but it exhibits a deep incision in 

 the atrophied zone. This incision is not separated from the end of the 

 red band corresponding to spot 5th, as it is in filipendulae, because there 

 exists no primary band to do so, but it obviously is homologous to spot 

 6th. These two observations, which are the counterparts of each other, 

 show very clearly that in filipendulae the marginal band is constituted 

 both by that of the nervural and that of the transverse pattern, but 

 that the former is usually (or specifically) narrow in the atrophied 

 zone, so that spot 6th can only be obliterated when the true pattern 

 acquires the high degree of development it has in stocchadis. Another 

 character pointing to the same conclusion is that when spot 6th is 

 reduced to a very small size, its last vestige in the darkest forms of 

 stoechadis is more usually quite at a distance from spot 5th, whereas 

 in subspecies filipendulae and in forms of stoechadis more similar to 

 filipendulae it is often very near or even confluent with it. In the first 

 instance it is clear that reduction is due to broadening of that band of 

 the true pattern, which extends between spots 5 and 6, and that the 

 nervural pattern has nothing to do with this process. It seems 

 reasonable therefore to suppose that also in the second instance the 

 true pattern as a rule invades the 6th spct by the broadening of its 

 marginal band and that the nervural pattern only joins in this process 

 in rare cases, in which it is unusually developed and behaves as in the 

 darkest achilleae, Esp., tending to abolish the incision of the atrophied 

 zone from the outer-side inwardly. 



Other instructive observations we can make by comparing 

 successively the underside of hindwings, the upperside of same, the 

 underside of forewings and the upperside of same, especially in the 

 dark forms of stoechadis. We find that these are four progressive 

 grades in the extent of the same markings. 



From all these remarks and many others one can, to my mind, 

 conclude that the principal variation of filipendulae consists in a 

 dissociation of the nervural and of the true or transverse patterns, and 

 in the consequent development in the extent of that of the two which 

 predominates. Schematically this process, pushed to the extreme, 

 could be pictured by an entirely red form, having also the forewings 



