Bulletin Wisconsin Natural History Society [Vol. 13, No. 2 
recorded specimens of T. semiaquea. Hence, if as suggested, a 
parallel in the distribution of T. semiaquea and T. cynosura exists 
then one would expect in going south to find a decrease in color 
markings of the wing. Such is actually the case as evident from 
the listed material. 
The situation is then as follows: 
T. semiaquea is a species whose range of distribution is Atlantic, from 
Florida to New Jersey (the Massachusetts records may be doubtful). In 
its simplest form the color markings reach beyond the triangle, gradually 
increasing in their extent until the culmination is reached in the northern- 
most forms where the color may extend to and beyond the nodus. 
T. cynosura is a species whose range of distribution is Carolinian to 
Transition, from Carolina and Oklahoma to Maine and Minnesota. In 
its southernmost localities the wings are nearly without marks, with a 
gradual investment which reaches its climax in the northernmost speci- 
mens, the color extending till the fourth antecubital (T know ol no speci- 
men in which a greater extent has been reached). 
The parallel is practically complete, an analogue in a smaller 
way to the distribution of Pantala flavescens and P. hymenea. 
It should be noted that occasional specimens are found which 
seem to be intermediates of the two species. It is not at all 
improbable that occasional interbreeding takes place. At best 
the two species are separable morphologically on only slight char- 
acters. The differences in the appendages of the males are mini- 
mal, and others are difficult to fix. The problem of these two 
species is akin to many similar cases of intimate relationship: 
it is difficult to fix any definite differences, because the limits of 
the variation of a variable character of one species lie within the 
limits of the variation of the same character of another species. 
In other words, markings, form, venation, etc., taken individually 
are non-distinctive; the collective definition must be the one 
chosen. 
In Tetragoneuria cynosura and T. semiaquea the color mark- 
ings in their development from south to north taken together with 
the geographical distribution offer a fairly reliable method of 
separation. 
In T. semiaquea proper there are several variations. Not upon 
any morphological basis whatsoever, but merely “as a matter 
of advisable convenience, and to prevent future synonymic en- 
