INTRODUCTION. . ix 
of Hiibner’s genera by Stephens in 1834-5. Stephens, admittedly dealing with a local 
fauna—that of Great Britain,—interpreted many of Hiibner’s genera by the light of 
such knowledge as he possessed, and it has been contended that he did not claim to 
be revising the ‘ Verzeichniss’ when he adopted Hiibner’s generic names and applied 
them to such British species as he recognized among Hiibner’s types; but, as in 
the case of other critical workers, it can be shown that Stephens was thoroughly 
acquainted with his subject, and by no means acted in the dark when he selected 
certain species to which he assigned Hiibner’s generic names. He specially stated 
that some of Hiibner’s genera required revision, and proceeded to apply his critical. 
knowledge to the task—in short, he did at least attempt to revise Hiibner’s work so far 
as the knowledge of the day permitted it and so far as such revision was required for 
the work in hand. In any case, but largely for this reason, we contend that Stephens’s 
limitations should be respected by subsequent authors, and this would probably be 
conceded after a careful study of his writings. We may perhaps go so far as to admit 
that an arbitrary rule is desirable for the future, but we contend that it should not be, 
and cannot be justly or advisedly, retrospective. For example, I consider that I should 
have had no right to cite pomonella as the type of Cydia Hitbner (Pr. Z. Soc, Lond. 
1897) if any other author had previously used Cydia with such limitations as had the 
effect of excluding that species; but Stephens having included pomonella among 
the three species of Carpocapsa, which he regarded as typical of ( ydia, it was 
obviously so selected by him and the genus was thus restricted to the type *. 
| For similar reasons Meyrick cannot, in my opinion, resuscitate Mompha Hiibner for 
conturbatella after Stephens had disregarded that species in his modified conception 
of Hibner’s genus. No arbitrary rules can rightly be made retrospective to the 
detriment of past study. Without such modification the arbitrary fixation of types 
strikes a death-blow at the whole system of priority, and the work of generations of 
critical authors is placed at the mercy of any future writer who may perhaps be 
comparatively unacquainted with the subject on which he writes. 
Is it too much to hope that by consistently advocating this view, and in each case 
giving reasons for selecting certain types of the older genera in cases where this has 
not already been done, we may in the end convince those representatives of inter- 
national opinion to whom the Rules of Nomenclature may next be referred that they 
‘would do well to lay down the principle that the arbitrary fixation of types can have 
no retrospective effect to the detriment of previous critical study, but can only be 
taken as applying to the present and to the future 2 
* Vide pp. 258-263—cf. Wlsm. Pr. Z. Soc. Lond. 1897 130; Cockerell New Mexico Agr. Coll. Bull. 25 
47 (1898); Busck Jr. New York Ent. Soc. 11 106-11 (1908) ; Fernald Gen. Tortr. 6, 19, 58 (1908), 
t Vide pp. 15-16—ef. Wlsm. & Drnt. Ent. Mo. Mag. 45 173-4 (1909), 
BIOL. CENTR.-AMER. , Heter., Vol. IV., June 1915, b 
