14 ME.MOI us OF TUK NATIONAL ACADEMY OF SCIENCES. 



Ill Eaeh'S impei'ialis, stuo-e I (PI. XLVII, fig. 2, ii). the midtubcrcle is lai-fre. highly devel- 

 opeil. each // being .siil)divid('d or two-headed. In stage III it becomes smaller in proportion, 

 a little longer than the diameter of the caudal horn at its base, and four-headed: it becomes 

 shorter in stage \\ and after the last molt is still more reduced and is forked.- but no higher 

 than broad. 



In C itheron la regal i!<(V\. LI V) this spine is, in accordance with the rest of the armature, 

 much more developed than in the other genera. It is in stages I. II, III about half the thickness 

 and length of the caudal horn. I'cpcating its shape and spinulation. while in stages W and V it is 

 about a third as long. 



In C. sjjiendeiis, in stages IV ainl la.st, it is about two-thirds as long as the caudal horn, 

 while in the last stage of C. sej)ulcralis it is much shorter, onlj' about one-fourth as long as the 

 caudal horn. 



T/i(> fhorac/'c '//'//lafun-. — We will begin with Adelocephala, whose mature larva is through- 

 out tile body the most spiny, the abdominal segments between the first and the eighth bearing 

 the caudal horn, being armed with large, and in certain species conspicuously colored, spines or 

 horns. The group is remarkable for the enormous thoracic and caudal horns in the earliest 

 stages. 



In stage I of .1. h/color (Pis. XLV and XLVI) and of Si/.«sphin.r moIu,a (PI. XLVII), the 

 remarkable features are the enormously developed second and third thoracic tubercles or horns, 

 which are three times as long as the caudal horn. While the specific and generic difierences are 

 given in detail under the special description of each life history, we may here give a comparative 

 account of the foi'ui and history of the thoracic spines in the Ceratocampina\ 



The prothoracic segment in the two genera already named is usually provided with setiferous 

 tubercles of even less than normal size, the dorsal ones no larger than the lateral ones, there being 

 .six on each side of tlie segment. But in the undetermined mature Brazilian larva (PI. III. fig. 1, 

 and PI. XLIX, tig. 4), they maj^ be found in stage I when discovered to be long and well 

 developed: they are distinct, fairh- long prothoracic dorsal spines. 



In Eacles and Citheronia, however, there is a great change: those of the dorsal pair being 

 enormously developed, and ending in a fork or two twin setiferous tubercles, repeating the 

 two forms of those on the two hinder thoracic segments. In Eacles the dorsal spines or horns are 

 between one-fourth and one-third as long as those behind, have two to three secondary tubercles, 

 and end in two long diverging setiferous branches or tubercles about a third as long as the entire 

 horn. This form is repeated in the subdorsal born, which is of the same general shape, but with 

 a shorter main .shaft. 



Of the horns behind, those of the mesothoracic segment arc a little longer than the meta- 

 thoracic ones. In Eacles the tubercles of the supraspiracular series are alike on each three 

 .segments in being primarily two-headed, but with such large secondary setiferous tubercles as 

 to make them appear five-headed. The infraspiracular spine on the first thoracic segment is 

 vei'y large, three-headed, while the one below is double headed. There are in all five tubercles 

 on each side of this segment. It is to be observed that in Eacles and Citheronia there is, con- 

 trary to Adelocephala and Syssphinx, a close similarity in shape and size between the caudal horn 

 and the thoracic horns. 



In Citheronia rec/a/t's^ tiu^ dorsal prothoracic horns are still more similar to those behind, 

 being nearly as long, and of identiciil shape and similarly spinulated. There is a marked differ- 

 ence in the development of the subdorsal horns of Citheronia, these being very much longer than 

 in Eacles, and only slightly differing in the shape of the bulbous end. The greater specialization 

 of the swollen end of all the eight horns as well as of the caudal horn in Citheronia is of 

 interest. The t)uU) is shaped like a chestnut, full, thick, forming the common base of the two 

 diverging tubercles, which bear specialized setie in the form of cylindrical straight rods, blunt 

 at the end; a seta of very characteristic shape. This style of specialized seta also occurs in the 

 thoracic horns of Adelocephala and Syssphinx, though in the caudal horn it does not appear, the 

 setic being of their primitive shape. 



