18 HAUSTELLATA. — LEPIDOPTF.RA. 



it is supposed to continue in the pupa ; that is, from September to April : 

 whereas the aestival brood remains in that state a few days only. 

 Before I conclude this discussion, let me ask how we are to reconcile the ano- 

 malous alternating increase and diminution of size, if, as is alleged, this 

 species and Po. Brassicsp are simply the vernal and aestival broods of the 

 same insect ? We know of no corresponding fact in any other department of 

 zoology, unless Po. Rapae and Metra (which are to each other, apparently, 

 what the two species under investigation are) offer an example *, but these 

 insects I presume are distinct, upon similar grounds to those which appear 

 to separate the insects that have promoted these observations ; and which, I 

 trust, will stimulate some persevering entomologist to investigate the subject 

 thoroughly ; as it becomes a question of importance to ascertain whether 

 P. Chariclea be really a distinct species, as it involves the curious physio- 

 logical considerations above noticed, which every unprejudiced person must 

 acknowledge are well worthy of attention, however he may inveigh against the 

 nicety which appears requisite to attend to in the discrimination of species ; 

 though in this instance locaUty can have nothing to do with the point at issue, 

 as the two species are found in the same fields at Hertford. 



My attention was first called to an investigation of the Pontile, 

 from observing many years since the specimens above alluded to in 

 Mr. Haworth's collection, who hinted his suspicions that they might 

 eventually prove distinct from Brassicse. I now possess several 

 specimens of var. a, all of which were taken by myself very early 

 in April at Hertford: Mr. Haworth's specimens were taken in 

 Derbyshire by the Rev. W. T. Bree, at the same period of the 

 year. I have recently noticed var. a <? of this species in other 

 collections, but confounded with Po. Brassicse. 



Sp. 3. Rapse. Alls ulbh- vel Jlavescentc-albidis, anticis supra apice 

 J'uscescente, basi pauluhan nigricante, subtus maculis duabus aid 

 una nigris, postids subtus Icetejlavescentibus basi nigro irroratis. 

 — (Exp. alar. 1 unc. 7 lin. — 2 unc. 6 lin.) 



Pa. Rapse. LinnL — Lexvin. pi. 26. — Po. Rapse. Steph. Catal. 



Very similar at the first glance to the preceding species, but usually much 

 smaller, and of a slightly dissimilar form and colour : the apex of the anterior 

 wings bears only a very sHght fuscous, dusky or black subtriangular, irregu- 

 larly defined spot, which does not extend along the hinder margin of the 

 wing : the male has also a conspicuous black spot, and the female two round, 

 and an obsolete elongate-triangular dusky spot, on the upper surface of the 



* Geometric illunaria and juliaria may probably be instanced, but they unfor- 

 tunately afford another proof of our ignorance; and, unlike the Pontiae, the 

 specimens which continue the longest in the pupa state exceed the others in 

 size ; the latter insect, which is the least, if the produce of the first, undergoing 

 all its changes in about three months. 



