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MEMOIRS NATIONAL ACADEMY OF SCIENCES. 



Vol. XII, 



segment; b, one from the seventh segment showing the medullary fluid supposed to be the 

 poisonous secretion, though there is no secretory cell visible at the origin of the spine; the spine 

 is dark and rather opaque. 



Stage III. (Described from an alcoholic specimen in the author's collection.) Length, 

 15 mm. ; with of head, 2 mm. The head is marked in general as before, but the hairs are smaller 

 and less numerous. The sinuous white band in front is much wider than before, being in front 

 fully three times as wide as the black line connecting the eyes; the band being narrower on the 

 sides above the eyes. The head is much narrower than the body, which is now stout and thick. 

 The two transverse black bands or rings on each of the thoracic and abdominal segments have now 

 disappeared, only faint traces of them being left here and there, the most persistent traces being 

 a minute linear black spot situated on the side behind the spiracles. The prothoracic tubercles 

 are black, and about half as long and large as the second and tliird thoracic dorsal ones, which 

 are whitish, with a black ring at base ; the lateral ones being black-brown. All the dorsal abdom- 

 inal tubercles are but a little smaller than the thoracic ones, and all, both dorsal and lateral, are 



black-brown, except the single large dorsal 

 tubercle on the eighth segment, which is now 

 very large and fully twice as thick as the largest 

 dorsal ones elsewhere, if not more; it has four 

 spines on each side, and two central ones. In 

 all the tubercles the spines are now short, and 

 no longer than the thickness of the tubercles 

 bearing them. The black curved line on the 

 side of the anal legs is now more curved than 

 before. 



Stage IV. (Described from Mr. Bridg- 

 ham's colored sketch.) Length, 20 mm. The 

 head is now yellow, with two black dots in front, 

 and a narrow black transverse line connecting 

 the eyes and antennae ; the head is about two- 

 thirds as wide as the body, which is now whitish. 

 The tubercles on the prothoracic segment are 

 black, and of the same size as those on the 

 abdominal segments, the latter (dorsal ones) 

 being now about one-half as long and large as 

 those on the second and third thoracic segmetits; the single median dorsal one on the eighth seg- 

 ment being a little thicker, and colored sulphur-yellow (Riley), like those on the second and 

 third thoracic segments. 



The curved black line is slenderer than in stage III. All the legs, both thoracic and abdom- 

 inal, are pale yellowish. 



Stage V, and last: Length 45-50 mm. In its final shape, the body is cylindrical, tapering 

 toward each end, and not so stout and thick as in Samia, or Telea, or Actias, or Attacus, and the 

 tubercles are smaller, smoother, and without the conspicuous large spines present in the genera 

 named, while the dorsal abdominal tubercles are smaller than in any other genus of Attacinse 

 known to us. In its larval characters the genus is the last and most specialized of a series begin- 

 ning with Saturnia (S. carpini) and including Samia and Philosamia. 



The head is small, being a little less than one-half as thick as the body, and now is with- 

 out any black spots. The black dorsal prothoracic and abdominal tubercles are much shorter 

 than in stage IV. The dorsal prothoracic ones are mere black spots, not even rising into low 

 warts; the two lateral ones on each side are much larger than the rudimentary dorsal ones, 

 rising into low conical shining black tubercles no higher than wide. The homologous lateral 

 tubercles on thoracic segments 2 and 3 are larger and more prominent than those on abdominal 

 segments 1 to 7. The rudimentary black dorsal tubercles on abdominal segments 1 to 7 are 

 low rounded conical shining black bosses, which are transversely oval at base, and not so high as 



FIG. 28. 



