92 COLLEMBOLA OF MINNESOTA 



has a very minute tooth. The color is exceedingly dark, appear- 

 ing a dead black to the naked eye. They live socially, as is com- 

 monly the case among the Achorutes, and often occur in great 

 numbers on the under surface of boards and in other moist sit- 

 uations. Once I found scores of them in the crevices of an 

 axe-wound in a living tree, where the sap was exuding enough to 

 supply the needed moisture. This is probably the most numer- 

 ous species of the genus in our locality. My specimens seem con- 

 siderably larger than those of the description, measuring 2.25mm. 

 in length, yet perhaps this is not surprising, as many of our col- 

 lembolans are somewhat larger than European specimens of the 

 same species. 



Achorutes socialis Uzel. 

 PI. X, Figs. 20-23; XI. Fi g- 3- 



1890. Achorutes socialis. Uzel, Thys. Bohemias, p. 69. PI. II, 16-19. 

 1893. Achorutes socialis. Schott, Palsearct. Coll. p. 81. PI. VII, 6-8. 

 1896. Achorutes socialis. Schaffer, Coll. v. Hamburg, p. 172. 



"Lower claw present. Upper claw large, slightly curved, 

 an acute tooth not far from the apex. Clavate hair over the claw. 

 Tibia set with long hairs, the clavate hair being longest of all. 

 Mucrones oblong, attenuate toward the end, blunt. Dentes less 

 than three times the length of the manubrium, thick, three times 

 longer than the mucrones. Five acute conical teeth on the 

 lower side of the dentes. Anal spines strong, about equalling 

 the papillae in length, slightly curved, obtuse. Antennae as long 

 as the manubrium, the segments successively increasing in 

 length, Ant. II truncate at the apex, III and IV less distinctly 

 separated. Body swollen, narrowed behind, the final segment 

 cylindrical. Dark blue, pruinose, feet, antennae and furcula pur- 

 ple. Length, 1-1.5 mm." 



Uzel mentions their living in very large colonies in low, 

 loamy ground and sometimes being found on snow. So far it 

 has been taken here but once, and that time by Mr. O. W. 

 Oestlund about the middle of April. Though there is no record 

 with the date, yet it is probable that they were in considerable 

 numbers as nearly thirty specimens were secured. The zigzag 

 row of five or six chitinous teeth on the dentes serves well to 

 distinguish it from any of the other species with which I am 



