NO. 2134. NORTH AMERICAN COLLEMBOLOUS INSECTS— FOLSOil. 495 



subequal, and basally confluent, the organ being smaller than one of 

 the eyes. Antennae shorter than the head; fu*st three segments sub- 

 equal in length. Fourth antennal segment with five short stout 

 olfactory hahs; three outer and two inner. Sense-organ of third 

 antennal segment as in figure 129. Unguis (fig. 130) stout, feebly 

 curving, unidentate. Tenent haii-s 3, 4, 4, Imobbed. Kami of tena- 

 culum tridentate. Dens (fig. 131) with five setae. Mucro (figs. 132, 

 133) three-fifths as long as dens, minutely tuberculate, elongate- 

 triangular, apically projecting and rounded, with a prominent ven- 

 tral lobe about one-third from the base. Anal spines (figs. 134, 135) 

 two, small (one-fourth as long as hind unguis), conical, curving for- 

 ward, on separated papillae, which are longer than the spines. Cloth- 

 ing (fig. 136) of sparse short curving setae. Length, 1.3 mm. 



On one specimen the left postantennal organ showed five peripheral 

 lobes, an abnormal condition. 



I sent specimens of this form to Walter M, Linnaniemi, of Finland, 

 who replied that they agreed in all essential character with the 

 European ScJwtteUa uniunguiculata, the only difi'erence being that the 

 cuticular tubercles seemed to be somewhat larger in our specimens 

 than in his. He kindly sent me a European example of the species, 

 from which I was able to confirm my determination of the American 

 form. 



I have found this species in large colonies at the base of apple, 

 maple, and hackberry trees. 



Illinois. — Urbana, April 16, May, October 6. Savoy, October 26. 



Genus XENYLLA Tullberg. 



Xenylla Tullberg, 18G9. 

 Eyes five on each side. Postantennal organ absent. Unguiculus 

 absent. Furcula small, not reaching the ventral tube. Dens and 

 mucro confluent in some species. Anal spines two, small; present in 

 most species. 



KEY TO SPECIES OF XENYLLA. 



Dens and mucro confluent maritima, p. 498. 



Dens and mucro demarcated by an articulation. 

 Apex of mucro simple, not strongly hooked. 



Anal spines large, one-fourth as long as hind unguis baconae, p. 496. 



Anal spines minute. 



Lamella of mucro broad (fig. 154); unguiculus represented by a rounded 



tubercle ivelcki, p. 497. 



Lamella of mucro narrow (fig. 141); vestige of unguiculus 



absent kuinicola, p. 496. 



Apex of mucro strongly hooked (fig. 161) gracilis, p. 497. 



