19 



morning ot" the fifth day it was found nearly dead, shght move- 

 ments of the feet and abdomen being perceptible. 



Harpalus caliginosus (Fabr.), beheaded at eleven and a 

 half o'clock in the morning was alive at half past nine in the 

 evening. It lived from fifteen to twenty hours. 



Clytus rohiniae Forster, After being beheaded it lived 

 twenty-four hours. 



Hylohius pales Herbst. After being beheaded it lived nearly 

 three days. 



Leptinotarsa decemlineata Say. On decapitation it lived two 

 and a half days. A. S. Packard, Jr. 



The Effect of a Few Common Gases on Arthropods. 



Carbonic Dioxide, COo. This gas acted differently upon 

 the several individuals, even of the same species. Coleoptera 

 generally grew weak gradually, and became motionless in from 

 eight to sixty seconds. Oniscus required a much longer time. 

 Such insects as recovered did so slowly, appearing as if intox- 

 icated and stiff in the joints. The following table will give an 

 idea of the comparative time required for the stupefaction and 

 recoverv of a number of species of Coleoptera. 



Species. 

 Plalynus atratus . . 

 Pleroslichus caudicalis 

 Slaphylinus maculosus 

 Cohosoma hasalis 



Motionless in 



15 s. . 



6 s. . 

 20 s. . 



20 s. . 



20 s. . 



20 s. . 



20 s. . 



20 s. . 



20 s. . 



20 s. . 



Remained in Gas 



. . 1 m. 



. . 2 m. 



. . 1 m. 



. . 1 m. 



. , 1 m. 



. . 1 m. 



. , 1 m. 



. . 1 m. 



. . 5 m. 



. . 5 m. 



Recovered at end of 

 . 5 m. 

 . 10 m. 

 . 2 m. 30 s. 

 . 2 m. 35 s. 

 . 3 m. 35 s. 

 . 4 m. 20 g. 

 . 4 m. 50 s. 

 . 6 m. 2 s. 

 . 11m. 

 . 12 m. 



Specimens of Oniscus, as may be seen by the following tab- 

 ular statement, behaved very differently in this gas, nor could 

 I discover any difference due to the adult or immature condi- 

 tion of the specimens. They were seized at first with twitch- 

 ings of the limbs, then rolled up in their customary way, some- 

 times unrolled and rolled up again, finally became motionless, 



