﻿NORTH AMERICAN SPHINGID^]. 113 



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wing is excised immediately on the escape of the imago from the cocoon, the remaining 

 portion is duly developed, and never witnessing the escape of air bubbles from the 

 cut extremities of the veins in the insect particularly observed, (Samia Gecropia,) I 

 was disposed to conclude, expansion did not take place in obedience to a voluntary 

 effort of the imago, but in consequence of some inherent property in the veins them- 

 selves. Subsequent dissection, however, revealed to me the existence of numerous 

 transverse septa or partitions, in the principal tracheal trunks of the wing of this 

 insect, extending from the base to the origins of all the branches, and consisting of 

 the same tissue as the tracheae themselves, which sufficiently explaining the cause of 

 the non-appearance of air bubbles, led me to retract my conclusion. The presence of 

 these septa is a very curious fact. They are extremely delicate, are attached to the 

 entire interior circumference of the tracheal trunk, and their presence difficult to 

 demonstrate, but I think the trunks of the wings in the species of the present family, 

 and those of the diurnal lepidoptera, are not provided with them, at least I have 

 never been able to find them, and excision of the wing in members of this family 

 might be accompanied by more positive evidence of voluntary effort, if the wings are 

 really expanded by the respiratory efforts of the imago. If this be true, every 

 endeavor to force air into the tracheae, would be indicated at the cut extremities of 

 the veins, by disturbing the globule of fluid which collects there. 



Early in my studies on this subject, I was led to give specific names to the various 

 branches of the principal trunks, indicating to a certain extent their origins and 

 distributions. I still regard it as preferable to the system in use amongst European 

 entomologists, and I shall retain them here, and give the names of the various trunks 

 and branches. The marginal nervure (1, Fig. 1, 2,) forms the anterior edge of the 

 wing, and is followed by the costal nervure (2, b") ; beneath and parallel to this again 

 is the subcostal nervure (3), and in this is found to occur most of the changes in the 

 neuration of the anterior wing. It subdivides into several ramifications or branches ; 

 those which are distributed to the costa or anterior margin of the wing being the 

 subcosto-marginal nervules (a', a') ; the one terminating in the tip of the wing, the" 

 subcosto-apical nervule (b) ; that immediately beneath it the subcosto post-apical (c'), 

 and the last branch the subcosto-inferior (c"). At the origin of this branch arises a 

 short transverse vein, called the discal nervure (d) ; it is a communicating branch 

 between the subcostal and the one beneath it, and gives rise at about its centre to the 

 disco-central nervule (cd), called also by Guenee, the independent. The next principal 

 trunk is the median nervure (4), which subdivides first at the point of anastomosis 

 with the discal into the medio-superior nervule (ws), followed by the medio-central 

 (mc), and medio-posterior (m p). The last nervure is the submedian (sm), sometimes 

 simple, sometimes bifid at the base. In the posterior wings of the Sphingida' 1 , in 

 addition to the foregoing, there is the internal nervure (£), and a short communicating 



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