334 NEW ilYKIAPODS FROM INDIANA. 



size, cyliudrical, length equal to the diameter. The last joiuts are coni- 

 cal and very small. The length of the four tarsal joints is equal to the 

 greatest diameter of the tibia. The femur and tibia are white and not 

 l^ilose, the hook is brown and pilose. 



I have recently examined seventy-four si)ecimens of that group of 

 Strigamia which is characterized by pits on the cox;© of the caudal legs. 

 I placed those together which had the same number of legs and the 

 caudal legs alike. 



The result was as follows : 



Specimens. 



1 . Legs 37 pairs ; caudal legs, stout . , 1 



2. Legs :39 pairs ; caudal legs, stout 5 



3. Legs 37 pairs ; caudal legs, slender I 



4. Legs 39 pairs ; caudal legs, slender 1 



5. Legs 41 pairs ; caudal legs, slender 2 



6. Legs 47 pairs ; caudal legs, slender 1 



7. Legs 49 pairs ; caudal legs, slender 10 



8. Legs ')! pairs ; c andal legs, slender 12 



9. Legs 47 pairs ; ca udal legs, stout 8 



10. Legs 49 pairs ; ca udal legs, stout 3 



11. Legs 67 pairs; caudal legs, stout 1 



12. Legs 09 pairs ; caudal legs, stout 6 



13. Legs 71 ])airs ; caudal legs, stout 2 



14. Legs 71 pairs ; caudal legs, slender - 12 



15. Legs 73 pairs; caudal legs, slender 9 



It will be observed that these easily divide into three groups, Xos. 

 1-5 having 37-41 pairs of legs; Nos. G-10 having 47-51 pairs of legs, 

 and Xos. 11-15 with 67 to 73 pairs of legs. It is a striking fact that not 

 one specimen out of the seventy-four has an even number of pairs of 

 legs. It will be noticed that in each group the ditfereniie in the num- 

 ber of pairs of legs is 2 or 4. Assuming that the specimens with slen- 

 der caudal legs are females and those with stout caudal legs males, it 

 will be seen that in the first group the females have 41, 39, or 37 pairs 

 of legs ; the males have 39 or 37 pairs of legs. In the second group 

 the females have 51, 49, or 47 pairs of legs ; the males have 49 or 47 

 pairs of legs. In the third group the females have 73 or 71 pairs of 

 legs ; the males have 71, G9, or G7 pairs of legs. 



In each groui) the specimens with the largest number of legs are 

 females, those with the smallest number males. But in the first and 

 second groups there seem to be females that have as few pairs of legs 

 as the males that have the fewest ; a glance at the first table will show 

 that there is but one specimen of this kind in each of the groups (]!?^os. 

 3 and G). It would appear then that adult females have two more i)airs 

 of legs than adult males and that these animals grow by the addition 

 of two pairs of legs, and therefore two segments at one time. Whether 

 these conditions will hold good for the whole genus or the whole family 

 I do not know, but I have reason to believe that it is the rule for males 

 to have fewer legs, by two pairs, than the females. 



Indiana University, March 10, 18SG. 



