12 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



minute secondaiy setiferous tubercles, and it is difficult to distinguissii the primary ones, wliose 

 growtii has become retarded or stationary, from the latter set, since they are so reduced in size. 



To enter more into details, while the tubercles of the anterior dorsal pair (lig. 1) in stage I 

 are already large and much specialized, the integument crenulated or wrinkled, the seta finely 

 spinulated, while the long tubercle sends off a posterior tine or spur near the base; on the other 

 hand, the tubercles of the hinder pair (ii) are minute in comparison and primitive in shape, the 

 tubercle itself a simple cone and the seta simple hair-like. Both sets of tubercles (/ and //) occur 

 on abdominal segments S and 9, the caudal horn on 8 being a highl}- modified tubercle /. The 

 same relations exist in stages II, III (figs. 2, 3, //). In stages IV and V, or the last instar, tubercles 

 ii are difficult to distinguish from the secondary ones, which are rather thickly crowded over the 

 dorsal surface; thej' can be distinguished on abdominal segment S directly behind and near the 

 base of the caudal horn. It may be observed that all the thoracic and abdominal horns are in 

 Adelocephala hypertrophied tubercles /, and this will apply to the Ceratocampidas in general. 



In tS'/saj'/ini.r molimi, stage I, tubercles // are wanting on abdominal segments 1 to 7, though 

 present on segment S behind the caudal horn. This atrophy of // at once clearh' indicates that 



Fig. 1. — Head and first five trmik-segnieiits of Schizura cimcmna, showing tlie 

 arraBgement of tubercles i-vii. 



this genus is a later, less primitive form than Adelocephala, a view corroborated by other 

 characters. 



In EaclcH imperkdh, which, generally speaking, has evidently almost directly descended from 

 Adelocephala, the tubercles ii are absent in all the stages on abdominal segments 1 to 7. On 

 segment 8 the tubercles // are situated next to the caudal horn and are of good size in stages I, 

 II, and all the later stages, being about as large as tubercle /// on the side of the segment. 



In Citheronia regaliH there are no tubercles ii on abdominal segments 1 to 7, but they are in 

 stages I to V on segment 8. In stage I they arc about one-half as large as the caudal horn itself. 

 In stages II and III (PI. LIV) they are large and branched, while in the last two stages they 

 become reduced, until in the final stage they are about as long as the caudal horn is thick at 

 its base. 



These tubercles (//) are present on the eighth abdominal segment in V. f<ejjii/e/'(ih's in all 

 stages; in C. splendens, stages IV and V (PI. LV), and in the last stage of C. laocoon (PI. LV). 



The species of Anisota form a side branch situated somewhat of!' the main evolutional track, 

 having undergone a greater reduction of tubercles in the larval state and of the maxilhc in the 

 imago than any of the other CeratocampinEe. Yet in the first larval stage of each of the four 



