THE CATP:RriLLAR : INTERNAL ORGANS. 25 



duct running hack along the sides of the alimentary canal, in a straight, 

 slightly wavy or tortuous course, to a point varying from the middle of 

 the thoi-acic to the hcginning of the ahdominal segments ; and second, of 

 a larger hut still very slender sometimes flattened tuhe or vessel pro[)er 

 (though scarcely larger in Hamadryas and Aglais), which has at first an 

 irregular course but runs beside the stomach to a point of attachment on 

 the same, generally in the sixth abdominal segment, terminating in a 

 slender thread. It has the greatest and most complicated de>'elo[)ment in 

 the skippers which spin more silk than others. In Epargyreus, for 

 instance, the vessel begins to expand as it enters the abdominal region, and 

 continues of the same diameter, as far as the beginning of the fifth abdo- 

 minal segment ; then it turns abruptly back upon itself, above its former 

 course, as far as the front of the second abdominal segment ; again turns 

 back with equal abruptness, above its previous course, and, diminished to 

 nearly one-half its former diameter, extends nearly to the middle of the 

 third abdominal segment ; it then turns upward at right angles along the 

 walls of the stomach to the middle of the sides of the same, or a little 

 higher, and again resumes its general backward direction ; on this it 

 extends, with a slightly Avavy course, as far as the end of the stomach, 

 when it turns downward and inward again and soon terminates in a blunt 

 tip, its extremity scarcely slenderer than its width when it is freed from the 

 coils on the sides of the stomach. The coiled or reversed portion covers a 

 distance of 5.75 mm. The initial duct is 9.5 mm. long, the stouter part 

 of the vessel 12 mm. long, and the slender terminal portion 11.5 mm. 

 long. 



The length of the initial duct is rarely so long as here and in Hamadrj^as 

 is only about one-seventh of the whole, while the length of the whole varies 

 from a little over 12 mm. in Eurymus, to as much as 65 mm. in Anosia. 

 In all other species examined the sudden change of direction found in 

 Epargyreus on the thu'd abdominal segment is wanting, the second abrupt 

 reversal of direction being the last. In some, as in Callophrvs and Euphoe- 

 ades, the stouter part of the vessel — always the part before any reversal 

 of direction — lies wholly upon the ventral surface beside its mate, but in 

 others the two lie removed from each other in the lower portion of the 

 sides. There is considerable variation too in the point at which the first 

 and second reversals occur ; in some the first is at the second abdominal 

 segment (Hamadryas, Polygonia, Callophrys), in others at the third 

 (Eurymus, Euphoeades), while in Epargyreus it is at the fifth : the second 

 reversal is always at the first or second abdominal segment ; and beyond 

 this point the narrowing tube has always a more or less tortuous course. 

 Throughout, the alimentary canal is closely hugged. 



Reproductive system. The organs of generation, as far as they are 

 developed in the mature male larva, consist of a pair of compound organs, 



