Royal Microscojncal Society. 271 



action of chloroform. I apply its four anterior tarsi to the interior 

 of an air-pump receiver. By pressing these slightly with the side 

 of a needle they adhere firmly to the glass, and the insect remains 

 suspended in its interior. I now exhaust the air, and the insect 

 still remains suspended. It is necessary to render the insect insen- 

 sible, otherwise it voluntarily detaches itself. To my mind this 

 exj)eriment is quite conclusive. 



The evidence aiforded by the print of the foot of Dytiscus upon 

 a clean glass slide is very conclusive, as every hair leaves an im- 

 pression in a viscid semi-fluid material upon the glass. The frin^-es 

 on the large disks are usually loaded with an abundant suj)ply of 

 this viscid glue. 



Again, if the suckers be examined whilst in action, they will be 

 found either to contain air or fluid, or to be aj)plied quite evenly to 

 the surface on which the insect is holding. This may easily be 

 done with an aquarium microscope, or by enclosing the insect in a 

 large live-box, with its feet upwards. 



It will probably be argued that a partial vacuum may be 

 formed by the elasticity of the suckers themselves ; but, admitting 

 this to be the case, its only effect would be to cause an increased 

 flow of viscid fluid from the surface of the disk, and hence it could 

 not aid the insect in adhering to any surface. 



The nature of the adhesive fluid has not yet been ascertained, 

 but it coagulates rapidly, is insoluble in water, and solidified under 

 that fluid. Its surface is shghtly greasy, so that water runs off 

 from it, and it cannot be wetted. I have been unable to find any 

 solvent that will dissolve it. 



In conclusion, I may remark, that I have several times found 

 beetles which have lost many of the tarsal disks, then- places being 

 marked by dark-brown chitinous cicatrices. I think this is due to 

 the insects having become too firmly glued to then- mates during 

 copulation, so that they have been unable to escape without leaving 

 their disks behind them. This closely resembles the adhesion of 

 flies to our window-panes in autumn ; the tarsi becoming so firmly 

 fixed in enfeebled insects that they are unable to escape. 



