June, 1906.] 



Key to the Order Thysanura. 



549 



BB: Saltatorial organ absent. 



JJ: Legs very short, not visible fnMn 

 above. Gen: 9 (41) Brachysius. 

 HH: Terminal spur present. 

 1 : 2 terminal spurs. 



Gen: 10 (42) Xenylla. 

 II: More than 2 terminal spurs. 

 J: 3 terminal spurs. 



Gen: 11 (43) Friesae. 

 JJ: 4 terminal spurs. 



Gen: 12 (44) Oudemansia. 

 Fam.:8 APHORURIDAE. 



C: Mouth-parts not placed cone-like under the head. 



Gen: 1 (45) Aphorura. 

 Gen: 2 (46) Anurophorus. 



CC 



D: Tarsus with 2 distinct claws. 

 DD: Tarsus with 1 distinct claw. 



E: Post-antennal organ absent. 

 EE: Post-antennal organ present. 



F: Terminal spur present, post-antennal organs placed i 

 rows. Gen: 3(47) Tullbergia. 



FF: Terminal spurs absent, post-antennal organs in circles. 



Gen: 4 (48) Anurida, 

 Mouth-parts appearing cone-like on under side of head. 

 D: 3 ocelli on either side of head. Gen; 5 (49) Neanura. 



DD: Ocelli absent. 



E: Post-antennal organs present. Gen: 6 (50) Aphoromma. 



EE: Post-antennal organs absent. Gen: 7 (51) Tetrodontophora. 



EXPLANATION OF DRAWINGS. 



The terminology used is practically the same as in other groups of 

 insects, with the exception of the sub-order, Collemhola, which are 

 peculiar in that they possess a ventral sucker, and saltatorial appendage. 

 The following drawings were taken from the genus, Isotoma, which is one 

 of the nicst generalized of the entire group. 



Fig. 1. Saltatorial appendage. Fig. 2. Antenna. Fig. 3. Ventral 

 view of sucker. Fig. 4. Side-view of sucker. Fig. 5. Post-antennal organ. ^ 

 Fig. 6. Left eye spot showing the ocelli. Fig. 7. Foot, 



