THE rATEUnr.I.AR: INTERNAL ORGANS. 21 



about llic trout ot'tlic alxloiiiiiial r('_ii;ion in Ano.sia and Callophrys, to near 

 tlif middle of tlic third alxloniinal sei^nicnt in Epargyreus ; lierc it hends 

 upon itself and rctui'iis in a (similar manner, a little higher up, to tlie point 

 from whicli it started ; the two otlier branches, whicli are a little smaller 

 than the first, extt'ud forward and then haekward in a similar manner and 

 to a somewhat similar distance, sometimes one of the three threads reach- 

 ino' farthest forward, sometimes one of the others, according to the tribe ; 

 one of the in)per branches passes along the u])per outer portion of the 

 stomach, the other along its side; all thi-ee branches i)ass outside the tra- 

 cheal tubes which invest the stomach, and when all have returned to the 

 point from whicli thev started, the extremities of the three are collected 

 with those of the opposite side in a single intricate convoluted mass en- 

 velo[)ing the intestine, and covering also the whole siu'face of the colon 

 with their more delicate terminal threads. When the })Osterior part of the 

 alimentary canal is pressed, Avhitish particles can be seen to move in an 

 irregular manner within the mal[)ighian vessels. In the characteristics of 

 their main portion, the mal[)ighian vessels are much slighter and shorter 

 in Euphoeades and Epargyreus than in the higher butterflies. 



Respiratory system. — The respiratory organs of caterpillars consist of 

 tracheal vessels, — cylindrical tubes composed of closely compacted, shining, 

 silvery, spiral threads, enveloped, or at least the principal stems, by the 

 thinnest possible investment and ramifying endlessly ; they have their 

 origin at the spiracles, situated on either side of the body on the lower 

 portion of the sides of the first thoracic and first eight abdominal segments 

 — in the last segment a little higher np the sides than in the others, and 

 especially so in the Lycaenidae. The tracheal trunks di\ide at their very 

 origin into a considerable nnmber of eqnal or nearly equal branches, which 

 at once push their way into different portions of the neighboring organs, 

 presenting an appearance resembling the aerial roots of some tropical tree ; 

 most of them reach the stomach and, diminishing abruptly in size, at once 

 branch at Avide angles and ramify all over it, every fold or lobnle being 

 tracked by two or three of the finest of the threads ; the intestine is trav- 

 ersed only by the finer tracheal tubes ; other shorter branches permeate the 

 floating organs, attach themselves to the muscles and the nerves and track 

 along the cord-like appendages. Each set of tracheae is connected at its 

 base with the set in front of and behind it by a tube as large as any of 

 them, which emits several short l)ranches ; thus if any spiracle is closed by 

 accident its neighbors may do service for it. 



These vessels arc somewhat modified in the anterior portion of the body ; 

 tiie tracheae of the first abdominal segment are larger and branch more 

 extensively than those of any other segment (although the spiracle is no 

 larger than the others) their ramifications extending to the anterior ex- 

 tremity of the stomach ; while those of the third and second and especially 



