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 as the fore-tarsi can be 4- jointed and the others 5- jointed, or only the 

 hind tarsi 5- jointed, while the others are 4- jointed. These varying conditions 

 are especially significant in division of the group Oleocharini . The indi- 

 vidual joints of the tarsi are most often round, however sometimes broad 

 and flat, the latter partly depends on the mode of living and sex of the 

 species (cf. Hygronoma , many Stenus species, fore-tarsi in the d^ of Fhi- 

 lonthus et al.) As a rule the joints interchangeably differ in length, which 

 not infrequently, espicially in regard to the hind tarsi, is taken into con- 

 sideration in the key to genera and species. 



C. The hind body ( abdomen) (see Pig. 1 and Fig. 5), which adjoins the 

 metathorax, consists of many joints (se'jments) with a dorsal part, dorsal 

 joints (dorsal segments, tergites) and a ventral part, ventral joints (ven- 

 tral segments, sternites). The joints are mutually connected by a membrane 

 which affords the great flexibility of abdomen (see preceding). The joints 

 are chitinized i.e. covered by a horny shell, which however is not devel- 

 oped on the entire first dorsal joint and base of the second, where abdomen 

 is protected by the elytra. Also in the species with long elytra the shell 

 on the covered joints is more pergamenous than horny and less hard. The 

 number of abdominal segments should, in a^eement with the ur-type of in- 

 sects (cf, t, Rftd. Lepiema saccharir. q. L., silverfish) be 10; but as some 

 segments as well dorsal as ventral are either connate with the metathorax, 

 or otherwise reduced, so that the number of true or distinct Segments are 

 differently understood, h'richson first counted 8 segments, later 9; Thom- 

 son and SchiiSdte count only 7 true segments; Kraatz declares, that 9 seg- 



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