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XVII. On the forms of Zygena Trifolii, with some re- 
marks on the question of specific difference, as 
opposed to local or phytophagic variation, im 
that genus. By T. H. Briaas, B.A. 
[ Read 6th November, 1871.] 
In the ‘Zoologist’ for 1861, Mr. Newman observes, 
touching another Zygena, that “it is a dangerous thing 
to write about our British Zygene, if anyone incline to 
take up the genus, I heartily wish him well through it.” 
And yet I am about to ask aid from Lepidopterists 
generally, in working out some curious facts connected 
with this, confessedly, difficult genus—difficult, because 
of the similarity of the perfect imsects themselves, more 
so by the similarity and variation of their respective larve, 
and yet even more so by the great confusion of their 
synonymy; the difficulties are crowned by the fact of an 
unusual and extraordinary affinity existing between the 
different so-called species, and the frequent occurrence 
of intermediate forms or hybrids—as yet, I cannot say 
which—that are found amongst them. My theory and 
proposition is, that two permanent forms of a Zygeana 
now existing in England, and confused under the special 
name T'rifolii, have an equal right with Loniceree to the title 
of Species. 
In the ‘Entomologists Annual’ for 1862, some re- 
marks by Prof. Zeller in the ‘Isis’ for 1840, are 
translated by Mr. Stainton, in which we find the follow- 
ing words,—“ Since that Nature, in the formation of 
species of Zygena (productive or reproductive) is not yet 
at an end, appears to me conclusive, from the constant 
copulation of specimens of different species without con- 
straint, and when in a condition of perfect liberty.” 
Uudoubtedly true as the fact is upon which Zeller 
bases this theory, it is somewhat difficult to follow his 
reasoning. 
Once admit that a form has become a species, and 
Nature is at an end, so far as relates to the formation of 
that species ; the progress of Nature, then (if any) is only 
to widen the separation. The sexual union of forms 
might be of common occurrence, but the fact is, the 
examples on record are not what we consider forms, but 
well-defined species, as subsequently mentioned by Bois- 
duval. Such a union would be strongly suggestive of 
TRANS. ENT. soc. 1871.—ParT Iv. (DECEMBER.) GG 
