STUDIES ON THE MALE TARSUS IN SOME ADEPHAGOUS 

 COLEOPTERA. 



By H. F. WIOKHAM. 



Among many of the families of Coleoptera the tarsi of the 

 males are modified in various ways, the better to secure their 

 hold upon their mates during the act of copulation. In many 

 genera of terrestrial Adephaga the joints of the middle or 

 anterior tarsi, or both, are dilated and furnished beneath with 

 pubescence, quite possibly glandular, which must aid them 

 greatly in maintaining their place. When, however, we come 

 to the Dytiscidas, we find the most wonderful and beautiful 

 transformations undergone by this sexual pubescence; it often 

 takes the shape of expanded palettes, or "suckers" as they 

 are sometimes called, which offer a large and mobile surface 

 for the spread of a peculiar viscid fluid which secures immedi- 

 ate and firm attachment to any smooth surface to which they 

 may be applied. The polished surface of the females of these 

 insects, necessar}^ for freedom of motion through the water in 

 which they live, offers a perfect basis to which these disks 

 may be made to adhere. 



A very interesting article on the structure of the foot of 

 Dytiscus has been given by Mr. B. T. Lowne in the Trans- 

 actions of the Royal Microscopical Society for 187 1. He has 

 demonstrated the presence of a gland in the interior of the 

 foot, which secretes a viscid fluid which is carried by ducts to 

 the nipple-shaped attachment on which the base of the colu- 

 mella of the large palette rests. This columella is apparently 

 hollow and open along one side; it is enclosed in the elastic 



