50G PROCEEDINGS OF THE NATIONAL MUSEUM vol. 93 



in this genus. Color differences alone are seldom reliable for the 

 separation of species, but, in some cases, only color characters could 

 be found. 



The males of Tetrdstichus often exhibit good differences in the 

 antennae and genitalia, but males are so rare that a useful classifica- 

 tion cannot be based on them. Females of a given species are gener- 

 ally ten or more times as numerous as are the males; in one-third of 

 the species in this genus males are unknown, and in some forms males 

 apparently do not exist. Finally, the study of the species in this 

 genus is greatly impeded by the very poor condition of many of the 

 types. 



A. B. Gahan, of the U. S. Bureau of Entomology and Plant Quar- 

 antine, has taken an active interest in the completion of this synopsis, 

 and many of the decisions as to specific limits, validity of characters, 

 and synonymy have been made in consultation with him. He also 

 generously allowed me to make full use of his notes and a manuscript 

 key to part of the genus; the latter contained several valuable charac- 

 ters for the segregation of species. 



In 1843, Haliday 1 described the genus Tetrastichus in a paper 

 giving his somewhat preliminary classification of the chalcid-flies. 

 The genus is monobasic, with CirrospHus attains Walker clearly in- 

 dicated as the type. Walker apparently accepted this generic segre- 

 gate at once, as he published the description of a new species in 

 Tetrastichus the following year,- and, shortly thereafter, transferred 

 many of his species, previously described in Cirrospilus, to Tetrasti- 

 chus. 3 Walker, 4 also, treated Aprostocetm We«twood as a synonym 

 of Tetrastichus, but that, according to present-day standards of 

 taxonomic procedure, would be impossible, as Aprostocetus is the 

 older of the two names. 



Foerster, in 185G, 5 published his comprehensive classification of the 

 chalcids and acknowledged the fact that it was based largely on the 

 works of Haliday and Walker. Foerster, however, distributed the 

 genera of chalcid-flies among more than 20 families. Tetrastichus 

 was made the type genus for one of these families. The genera Trl- 

 phasius Foerster, Anozus Foerster, Pteroptrix Westwood, Trichaporus 

 Foerster. Ceramsus Walker, Baryscapus Foerster, Hyperteles Foer- 

 ster, and Tetrastichus Haliday were grouped together to form the 

 family Tetrastichoidae. 6 In his discussion of the genus Tetrastichus? 



1 Trans. Ent. Soc. London, vol. 3, p. 207. 1S43. 



2 Ann. Mag. Nat. Hist., vol. 14. p. 17. 1844. 



'■' List of the specimens of hymenopterous insects in the collection of the British Museum, 

 Chalcididae, 237 pp. in 2 vols., London, 1846-1848. 



4 / or. cit.. p. 7S. 



5 Hymenopterologische Studien, vol. 2, 152 pp., Aachen, 1856. 

 Loc. cit., p. 83. 



~ Loc, cit., p. 86. 



