71 



TRANS. ST. LOUIS ACAD. SCIENCE. 



of one species, easily rub oft", and perfect specimens, captured at 

 large, are uncommon. More careful comparisons made in 1S73 

 by Mr. Mann {Joe. cit.) between both sexes, established the spe- 

 cific differences of the two ; and further comparisons, by myself,* 

 of the preparatory states, showed these differences to be still more 

 remarkable than had been supposed. During the present year I 

 have been able to make still more careful comparisons, which 

 show the two insects to be so very distinct that they must be sepa- 

 rated generically. These differences are set forth in the follow- 

 ing comparative columns. They show that pometaria alone can 

 be retained in the genus Anisopteryx, and for vernata I have, 

 therefore, erected a new genus, Paleacrita. 



Paleacrita vernata. 



Elliptic-ovoid, the shell of deli- 

 cate texture and quite yielding; ge- 

 nerally appearing shagreened or 

 irregularly impressed ; nacreous, 

 and laid in irregular masses in se- 

 creted places. (Fig. 14, b.) 



Eg& 



Anisopteryx pometaria. 



Squarely docked at top, with a 

 central puncture and a brown cir- 

 cle near the border; of firm texture. 

 and laid side by side in regular 

 rows and compact batches, and 

 generally exposed. (Fig. 18, a, 

 b, c.) 



No prolegs on joint S. (Fig. 

 14. a.) 



Head distinctly mottled and spot- 

 ted, the top pale, and two pale trans- 

 verse lines in front. 



Body with eight superior, narrow, 

 pale, longitudinal lines barely dis- 

 cernible, the two lowermost much 

 farther apart than the others. 



Dorsum pale, with median black 

 spots; subdorsal region dark; stig- 

 mata] region quite pale. 



Piliferous spots quite visible and 

 large on joint 11, where the pale 

 lines generally enlarge into white 

 spots immediately in front of them. 



When newly hatched dark olive- 

 green or brown, with black shiny 

 head and cervical shield. 



With a pair of short but distinct 

 prolegs on joint S. (Fig. 18, /.) 



Head very indistinctly spotted, 

 and dark on top. 



Only six superior, broad, and 

 very distinct pale lines, those each 

 side equidistant. 



Dorsum dark, without ornament : 

 subdorsal region pale; stigmata) 

 region dark. 



Piliferous spots subobsolete. 



When newly hatched pale olive 

 green, with very pale head and cer 

 vical shield. 



7th Mo. Ent. Rep., pp. Sc-SS. 



