STUDIES IN TBTRAGONBURIA (ODONATA). 

 By Richard A. Muttkowski. 



A revision of the genus Tetragoneuria presents a series of 

 difficulties which fully equal those of other genera of Odonata, 

 such as Argia, Ncurothemis, Brythrodiplax, Pcrithemis, etc. The 

 close resemblance of the species, the generalized genitals and but 

 little specialized anal appendages, and the variability of wing 

 markings and wing venation are factors which tend to make a 

 mechanical separation of the species difficult, if not impossible 

 on occasion. 



The genus Tetragoneuria has always, more or less, belonged 

 to the category of "Splitters' and Lumpers' Paradise". The 

 tendency to regard color extremes as indicating specific validity, 

 as also the other extreme — to regard them as a series showing the 

 gradual development of one species — is well marked in the writ- 

 ings on the subject. Either tendency seems to have been based 

 on the amount of material available to the respective author. 



The present study had its origin in 1909, when the Milwaukee 

 Museum expedition to the St. Croix river furnished a series of 

 about thirty specimens. Coincident with this material some 

 specimens were received from Florida for determination, a fair 

 share of which fell to the Museum. This together with material 

 already on hand formed the nucleus of a brief study, in which the 

 following conclusions were reached : 



(a) The T-S} ot. as far as cynosura is concerned, is an unreliable 

 character. For the material showed all g-radations from a rudiment 

 of the T-stem to the fullest development of the T-cross. 



(b) The specimens from Florida are not identical with those 

 from northern states. 



(c) A query. What is the distinction between cynosura, basigut- 

 t(it<t, semiaquea and indistiheta (semiaquea as interpreted by recent 

 ai thor? ) ? Dr. .Martin's table (Cordnlines, p. 45, 1908) offered no help 

 in this matter. Strictly taken, over half of the specimens on hand 

 would be referable to indistincta Morse; on the other hand, the iden- 

 tity of the specimens of the St. Croix series was unmistakable. 



