1432 THE BUTTERFLIES OF NEW ENGLAND. 



while spiracles are ordinarily oval, and they present no opening in the 

 centre, but only, as far as I have been able to observe, a simple pit of 

 more delicate structure than the chitinous annulus itself. They are found 

 also in some Hesperidae in their earliest stage and sometimes also throughout 

 life. But for the tenuous structure of the pit in the centre, they would have 

 all the appearance of suppressed spines, and, indeed, the central pit seems 

 sometimes to be wanting, and we have simply a shining lenticle, similar to 

 those which are so common in the Papilioninae. But whether they should 

 be looked upon as structures on their waj^ to some use, or as effete struc- 

 tures, degenerated spines so to say, we have no facts at present to show, 

 and an explanation of their purpose is still to be sought. 



The discussion of these odd structures and curious arrangements of parts 

 in caterpillars may already have been extended to sufficient length, but I 

 should like to draw a moment's attention to two other special points in the 

 structure of caterpillars which are still enigmas. One is the purpose or 

 cause of the excessively constricted neck of caterpillars of the Hesperidae, 

 a universal characteristic and one that is widely different from the frequent 

 enlargement of this segment, as we find it in the Papilioninae, and to a 

 much greater extent in the Lycaeniuae. Another is the curious swollen 

 vescicle which hangs like a bag, a blunt, conical or transverse structure 

 below the first thoracic segment in advance of the legs. Various sugffes- 

 tions have been made with regard to this. It is a very common occur- 

 rence, perhaps not universal, with caterpillars, Ijut very much more highly 

 developed in some than in others. In those in which it is most highly de- 

 veloped, we have found no habit or jieculiarity which would explain its 

 purpose. It is ordinarily covered with gritty tubercles of a special struc- 

 ture, but as far as I have been able to see, contains no openings whatever. 

 Many other singular things about caterpillars needing explanation could 

 be given, especially as regards their coloring, but these will suffice to 

 show that there is yet a wide field open, even among our commonest forms. 



THORYBES BATHYLLUS.— The southern cloudy- wing. 



[White spotted tailed skipper (Mayuard).] 



Papilio bathyllus Smith-Abb., Lep. ius. (188C) ;— Mayii., Butt. N. Eugl., 53, pi. 7, figs. 



Geo., i : 43-44, pi. 22(1797);— Abb., Draw. lus. 75, 75a (1886). 



Geo. Br. Mus., xvi ; 47, pi. 173 (ca. 18(10). J^thUUi bathyllus Biitl., Eutom. luoiithl. 



Qoniloha bathyllus Westw.-Hew., Geu. inag., vii: 57 (1870). 



diurn. Lep., ii: 514, 534 (1852) ;— Lucas, Sagra Thoryhes bathyllus ScuAd., Syst. rev. Am. 



Hist. nat. de Cuba, 638-639 (1857). butt., 50 (1872). 



Eesperia bathyllus Morr., Syn. Lep. N. Papilio Abb., Draw. Iiis. Geo., Br. 



Amer., 106 (1862). Mus., vi : 70, figs. 94-95 (ca. ISOO). 



Eudamus bathyllus Herr.-Schaell"., Prodr. 



syst. Lep., iii: 67 (1868);— French, Rep. ius. Figured also by Glover, 111. N. A. Lep., pi. 



III., vii: 162 (1878); Butt. east. U. S., 369-370 29, fig. 11; pi. B.figs. 22, 23, ined. 



