DYTHEMIS. , 273 
Libellula tessellata, Rambur (nec Burm.), Ins. Névr. p. 89 (1842) °. 
Dythemis sterilis, Hagen, Syn. Neur. N. Amer. p. 317 (1861)"; Proc. Bost. Soc. Nat. Hist. xviii. 
p- 87 (1875) *; Calvert, Proc. Calif. Acad. Sci. (2) iv. p. 522, t. 16. figg. 52-55 (details ¢ ¢ ) 
(1895) °. 
Dythemis velox, var. sterilis, Calvert, Proc. Bost. Soc. Nat. Hist. xxviii. p. 310 (1898) ”; Proc. Calif. 
Acad. Sci. (3), Zool. i. p. 890 (1899) ”. 
Dythemis broadwayi, Kirby, Ann. & Mag. Nat. Hist. (6) xiv. p. 227 (1894) ”; (7) ili. p. 365 (1899) *. 
Dythemis nigra, Martin, Ann. Soc. Ent. Fr. Ixvi. p. 590 (1897) **. 
Dythemis velox, var. tabida, Calvert, Proc. Bost. Soc. Nat. Hist. xxviii. p. 310 (1898) ”. 
Dythemis velox, var. nigrescens, Calvert, Proc. Calif. Acad. Sci. (3) Zool. i. p. 890 (1899) "°; (2) iv. 
p. 525 (1895) ". 
That the above names represent, in large part, colour-differences due to age appears to be demonstrated by 
the following evidence :— 
(a) Transitions in the colour of the frons from pale green and luteous through brown to metallic-blue 
are furnished by Hagen’s types of velow (Calvert *) and by the females from Lanquin, Belize, Rio 
Cocula, Presidio (V.C.), Zapote, San Felipe, and Teapa (April) in the order named. Specimens of 
one or the other sew from Temax, Teapa, Belize, Gualan, Mazatenango, Surubres, show distinctly 
the beginning of blue reflections on their brown or luteous fronts and vertices. 
(b) Without exception, individuals of both sexes having metallic-blue”'*’’, violet "*, or green * on 
vertex and frons have darker-coloured thorax and abdomen (7. ¢. are older) than do individuals 
with pale green®, luteous * ’, or brown frons and vertex. 
(c) Pruinose™ (i. e. old) individuals always have metallic-blue or violet on frons and vertex, while 
individuals with generally pale and light brown °* body-colours do not. 
(d) Individuals with pale brown’, blackish“, or pruinose’’ body-colouring, with pale green’, 
luteous ?, brown”, or metallic-blue™, -violet '*, or -green ** frons and vertex, occur in the same 
localities and often in the same month or on the same day, viz.: San José del Cabo (October)* ”, 
Tepic (October, November)" "*, Atoyac (April, May), Teapa (January, February, April), Tehuantepec, 
Mazatenango (February 3), Santa Lucia (February 2), San Pedro Sula (February 27). 
That variation in the extent of the coloured areas on the wings is independent of age is shown by the 
following :—Of Hagen’s five male types of velox from the Pecos River, which I studied in the M.C. Z. in 
1897, those with luteous vertex and frons, a stripe in front of the eyes, a metallic-blue point in the 
superior groove of the latter, have brown at the base of the wings half-way to the submedian cross-vein 
or less, brown at the apex extending farther in than the outer end of the stigma (Aug. 5); that with 
brown vertex and frons, the latter with some bluish reflection, has brown at base of wings as before, 
brown at apex of wings for a width of three cells (July 11); that with metallic-blue frons and vertex 
has almost no colour at base of wings, brown at apex for a width of four cells (Aug. 7). Hagen’s four 
female types of velox from the Pecos River have frons and vertex pale green, wings brown at base out to 
the submedian cross-vein, or not so far on the front pair; the brown at the apex reaches in almost to the 
inner end of the stigma (July 9), or in to but little farther than the outer end of the stigma (Sept. 11). 
The females from Gualan vary in the extent of brown at the apices of the wings from only one cell’s 
width (Jan. 12) to the entire apex inward: to within one cell of the level of the inner end of stigma 
(Jan. 14); both extreme females have vertex and frons yellowish and seem to be of the same age; that 
of Jan. 12 is a little larger. The males from Gualan, although much more numerous, show hardly any 
variation in the colours of the wings or body ; both sexes are of the form I described as sterilis °. 
That all the forms represented by the names above given intergrade, ontogenetically or individually, and are 
therefore one species, I have no doubt. Some slight geographical distinction into subspecies possibly 
* I have also before me a manuscript description of M. Martin’s type of nigra made and sent to me by 
Dr. F. Ris. 
