4l8 N. E. MCINDOO. 



species examined. As a rule the smaller the species, the larger 

 are the pores, comparatively speaking, and the fewer they are. 

 Likewise, the larger the species, the greater is the number of its 

 pores and the smaller they are. As a rule there are no generic 

 and specific differences, except variations in number of pores, 

 the amount of variation depending on the size of the individuals 

 compared. Judging from the sizes of the four water beetles 

 examined, the pores on their legs are fewer and smaller than 

 those on the legs of any other beetle examined. Pores were 

 found only on the trochanters of Cybister, while a few were also 

 seen on the femurs and tibiae of the other three water beetles. 

 The number of pores on the legs of these beetles are as follows: 

 Cybister — 49, Dineiites discolor — 65, Dineutes vittatiis — 98, and 

 Hydrophilus — 93. These numbers indicate that the better the 

 legs are adapted for locomotion in water, the fewer pores they 

 have. 



The small total numbers of pores of Osmus, Clinidium and 

 Cysteodemus are due to the absence of wings. In Osmus and 

 Clinidium more pores are found on the legs than might be sus- 

 pected. The tarsi of Osmus have more than the tarsi of any 

 other beetle while the tarsi of Clinidium have more than sus- 

 pected. 



The following table (p. 419) includes the family, name and 

 number, the olfactory pores on the legs, elytra, wings, and the 

 total number of pores of each of the 50 species examined. In 

 the preceding pages the beetles are usually referred to in this 

 table by their respective numbers. 



(c) Individual and Sexual Variations. 

 For this study five males and five females each of Harpalus 

 pennsylvanica and Leptinotarsa lo-Uneata were used. No indi- 

 vidual and sexual variations were found, except slight variations 

 in the number of pores. The total numbers of pores of the males 

 of Harpalus vary from 550 to 580 with 570 as an average; those 

 of the females of Harpalus from 575 to 699 with 628 as an average. 

 The average number of pores for males and females of Harpalus 

 is 599. The total numbers of pores of males of Leptinotarsa 

 vary from 665 to 780 with 722 as an average; those of the females 



