I 611 ) 



Now, with the exception of two species {kahneli from the Amazons, and pltalaecus 

 from Ecuador) all the tailed species of the vast gronp of American Aristolochia- 

 Swallowtails occur in the coantries from Costa Eica northwards, and in the 

 Brazilian fannistic snbregion (inclusive of Paraguay and Argentina). Is it at 

 all likely that in the Andesian and Amazonian provinces, from Bolivia to Costa 

 Rica and eastwards to the Guianas and Para, the tail is an unnecessary appendage 

 in these insects and has therefore been dropped, while it is a useful passive means of 

 defence in the other districts ? Considering further that these Aristolochia-feeders 

 are supposed to be practically immune, their nasty smell protecting them from 

 insect-feeders (perhaps not against inexperienced young individuals), it appears to us 

 certain that the presence of a tail in nearly all the Aristolochia-Papilios occurring 

 from Nicaragua northwards, as well as in almost every species found in the 

 Brazilian province, has nothing to do with a supposed usefulness of the tail as a 

 passive means of protection, and that accordingly the occasional absence of the 

 tail from Mexican specimens of phUenor is due to a physiological change of the 

 species in the southern districts of its range. P. philenor was originally doubtless 

 an inhabitant of the Atlantic district of the Nearctic Region ; the close morphological 

 connection between the Continental philenor, the Cuban devilliers and the Haitian 

 x:etes pointing decidedly in this direction. From this original home the species 

 spread southward and westward into Mexico, and at the Pacific coast again 

 northward as far as Northern California, Californian, Arizonan and Mexican 

 specimens differing on the whole slightly from eastern ones. 



The scales of the upperside of the forewing are denticulate in P. philenor, 

 except towards the hinder angle ; on the hind wing, on the contrary, the scales are 

 entire, except in the region of the tail and anal angle. On the underside the scales 

 are dentate on both wings, the inner area of the forewing excepted. The white 

 spots attached to the orange spots of the hindwing are homologous to the white 

 spots of F. polydamas, which stand in the same connection with the red spots 

 in this species. The basal dot of the hindwing of P. philenor, on the underside, 

 is found in all the near allies of P. poli/damas, the corresponding dot of the 

 forewing being also present in P. polydamas. The scent-organ of the male and 

 the genitalia of both sexes are essentially as in P. polydamas, being only slightly 

 different. 



The spring specimens of P. philenor appear to be on the whole smaller than 

 the later individuals, and bear always a row of spots on the upperside of the 

 forewing, this row being often absent from the males of the summer brood 

 (or broods). The hairiness of the body varies considerably, early Californian 

 specimens having quite a shaggy appearance. 



Scent-organ : the scales are smaller than in P. polydamas, those of the streak 

 of small scales situated along the naked streak being moreover less triangular. 



Genitalia: S. The lateral edges of the tenth tergitc are elevate in proximal 

 half, the distal half of the process appearing depressed in a lateral view. Harpe 

 with two processes as in P. polydamas, both short, pointed, the ventral one com- 

 pressed and broader than the dorsal process. ?. Hairy flaps in front of cavity 



large, connected with one another at base, acuminate, each bearing on the distal 

 side a carina which extends on to the membranous proximal wall of the cavity. 



For early stages, see literature under P. ph. philenor. 



Hah. United States, except the central district from Colorado northwards . 

 Mexicp, ' 



