320 PHYSIOLOGY. 



as Amara, the Zabrodea, Feronia;, and many others, merely those of 

 the anterior pair. Each of these groups exhibit new differences, 

 according to the number of the distended tarsal joints. We thus find 

 in the third group, in which the anterior legs only have distended 

 tarsi, sometimes four distended joints, as in FJaphrus, Blethisa, &c. ; 

 sometimes only the three first, as in Chlcenius, Amara, Feronia, &c. ; 

 sometimes the two first, as in Patrobus ; and lastly, the first alone, as 

 in Omophera, Latr. In addition to these differences, we observe in 

 the males of Harpalus, the Amarodea, Pcecili, and the entire genus 

 Feronia, a brighter reflection upon the elytra ; whereas those of the 

 female are duller, sometimes indeed, for example, Feronia (Abax} 

 striola, almost opaque. The same character is also found in the 

 majority of the water beetles, and which has sometimes occasioned, as 

 in Hydroporus parallelogrammus, Ahr., the separation of the male 

 and female as two species ; for Kunze described the male of this species, 

 which Ahrens had described from a female specimen as Hydroporus 

 cnnsobrinus*. The same is the case with Hydrop. picipes, Kunz. f, 

 and Hydrop. alternaus, Grav. ; the former is the male, the latter the 

 female, as specimens taken in copula prove. The differences of the 

 structure of the tarsi is tolerably analogous in both families ; thus the 

 males of the true Dytici (for example, D. latissimus, dimidiatus, punc- 

 tulatus, &c.) have three distended tarsal joints on the anterior leg; they 

 are also distinguished from their females by having smooth elytra, 

 whereas in the latter sex the upper half is in general deeply furrowed ; 

 in Cybister (Dytici Roeselii, Auctor.), on the contrary, the first pair 

 only has distended platter-shaped joints, and the female has no fur- 

 rows, but merely dull, scratched elytra. In Colymbetes the distended 

 tarsal joints do not form, as in the two other instances, a round patella 

 beset beneath with sucking cups, but they are long and extended, and 



* Neue Schvift. d. Hallisch. Naturf. Gesellsch, vol. ii. part iv. p. 61, 2. We may here 

 remark, en passant, that the following is the synonymy of this species : 



Hydroporus parallelogrammus. Ahr., Nov. Act. Nalens, vol. ii. fas. ii. p. 1 1 . 1 . 

 $ Hydr. consobrinus. Kunz., ib. fas. iv. p. 61. 2. 



Hyph. nigrolineatus. Schonh. Syn. Ins. 

 $ Hydr. nigrolineatus. Kunz., ib. p. 61. 1. 



Hyph. parallelogrammus. Oyll.,Ins. Sues., torn. iv. p. 08!). 13 14. 

 Hyph. nigrolineatus. Gyll. Ins. Sue?., torn. iii. add. p. 638. 

 Dyticus lineatus. Marsh., En torn. Britt. i. 426. 35. 

 t Ibid, Cl. 2. 



