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. 
XoTE — 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 distinctiy 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. 
Fam; 1. LEPISMIDAE. 
Gen. 1 (1) Troglodromicus. 
Gen. 2 (2) Machilis. 
SUB-ORDER, I. CINURA. 
B ; Body covered with scales. 
C; Eyes absent. 
CC; Eyes present’ 
D; Eyes large, contiguous or nearly so. 
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 (o) Anisosphaerae. 
CC: Caudal appendages, simple segmented filaments or sickle shaped. 
D: Caudal appendages sickle-shaped. Fam; 3. lAPYGIDAE. 
E : A single genus. Gen. 1 (6) lapyx 
DD: Caudal appendages many jointed filaments. 
Fam.: 4 CAMPODEIDAE. 
E: Two caudal appendages. Gen. 1 (7) Campodea. 
EE: Three caudal appendages. Gen: 2 (8) Nicoletia. 
AA: Mouthparts retracted, palpi not distinctly visible, antennae usually 4-8 jointed, 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 segment. 
D: Abdomen globular, only slightly longer than broad. 
Fam; ■). SMINTHURIDAE. 
E; Terminal segment of antennae short, with whorls of hairs. 
• Gen; 1 (9) Papirius. 
