546 The Ohio Naturalist. [Vol. VI, No. 8, 



be satisfactorily determined; and, partly from the fact that many 

 of the species vary greatly as to color, or the young of one species 

 resembling the adult of another. All this has had a tendency 

 to discourage further research. Adequate keys have been pre- 

 pared but the most of them have dealt only with Old World 

 species. 



The present key has not been thoroughly tested, but it is 

 hoped that it will aid somewhat the research in American 

 species. It has been adapted from ' ' Die Gattungen und Arten 

 der Apterygogenea (Brauer)," by Dr. K. W. v. Dalla Torre, 

 published in 1895, but I believe it will apply to most of our 

 genera. 



I desire here to extend my thanks to Dr. L. B. Walton and 

 Prof. Herbert Osborn for the valuable suggestions concerning 

 the preparation of this publication. The accompanying plate 

 has been made by my wife, who has given me the greatest assist- 

 ance throughout the entire work. 



Note — The following key has been prepared in advance of a more 

 extended work on the Thysanura of Ohio. Any suggestions or specimens 

 will be gladly received. 



KEY TO THE FAMILIES AND GENERA OF THE ORDER THYSANURA. 



A: Mouthparts well developed, palpi distinctly visible, antennae usually many jointed, 

 caudal end of body usually provided with a pair of jointed filamentous or forcep- 

 like appendages and without a ventral sucker. 



SUB-ORDER, I. CINURA. 



B: Body covered with scales. Fam: 1. LEPISMIDAE. 



C: Eyes absent. Gen. 1 (1) Troglodromicus. 



CC: Eyes present' 



D: Eyes large, contiguous or nearly so. Gen. 2 (2) Machilis. 



DD: Eyes small and separated. 



E: Caudal appendages very short. Gen. 3 (.3) Lepismina. 



EE: Caudal appendages nearly as long as body. Gen. 4 (4) Lepisma. 

 BB: Body not covered with scales. 



C: Abdomen without caudal appendages. Fam: 2. ANISOSPHAERIDAE 

 D: A single genus. Gen. 1 (5) Anisosphaerae. 



CC: Caudal appendages, simple segmented filaments or sickle shaped. 



D: Caudal apjiendages sickle-shaped. Fam; 3. lAPVGIDAE 



E: A single genus. Gen. ljc(3)^lapyx 



DD: Caudal appendages many jninted filaments. 



Fam.: 4 CAMPODEIDAE. ' 

 E: Tw(j caudal appendages. Gen. 1 (7) Campodea. 



EE: Three caudal appendages. Gen: 2 (8) Nicoletia. 



AA: Mouthparts retracted, palpi not distinctly vi.sible, antennae usually 4-8 jninted, a 

 forked sucker on the ventral side of abdomen, a saltatorial appendage usually near 

 caudal end of abdomen. (See drawings.) 



SUB-ORDER, II. COLLEMBOLA. 



B: Saltatorial organ present. 



C: Saltatorial organ attached on the penultimate abdominal segnicnl. 

 D: Abdomen globular, only slightly longer than broad. 



Fam:5. SMINTHURIDAE. 

 E: Terminal segment of antennae short, with whorls of hairs. 



Gen: 1 (9) Papirius. 



