PLATYPLAX.—ERYTHEMIS. 329 
Rambur. The difference in size is not great, and H. peruviana has been taken at 
Altamira at the same time that P. sanquiniventris flies. The case of these two species 
is like many of those among the Lepidoptera that have been described as instances of 
mimicry, but we have here as yet no observations bearing on the utility of the resem- 
blance. Structurally, P. sanguiniventris and F. peruviana differ in many respects, as 
may be seen by comparing their respective generic characters given on pages 203 
and 204, anted. 
ERYTHEMIS. 
Erythemis, Mesothemis pars, Lepthemis pars, Hagen, Syn. Neur. N. Amer. pp. 168, 170, 160 
(1861)*; Brauer, Verh. zool.-bot. Ges. Wien, xviii. pp. 368, 369, 723, 721 (1868)°; Kirby, 
Trans. Zool. Soc. Lond. xii. pp. 264, 304, 303, 302 (1889) °; Cat. Odon. pp. 40, 39 (1890) *; 
Calvert, Ent. News, xvii. p. 30 (1906) ’. 
Mesothemis, Calvert, Trans. Amer. Ent. Soc. xx. p. 225 (1893)°; Proc. Calif. Acad. Sci. (2) iv. 
p. 478 (1895) 7; Kellicott, Odon. Ohio, p. 92 (1899) °; Williamson, 24th Rep. Geol. Indiana, 
p- 250 (1900) °; Needham, Bull. 47 N. Y. St. Mus. pp. 507, 508 (1901) *. 
The grounds for employing the generic term here adopted have been set forth 
elsewhere °. 
Six species and one subspecies exist within our faunal limits; the characters of a 
seventh (credula) are added, as it also is likely to be found here. Two others, 
rubriventris, Blanchard *, and plebeja, Burmeister f, have been described from South 
America, but are too imperfectly known to enable a decision to be reached as to 
whether they are or are not distinct from the others. 
Synopsis of Specific Characters. 
A. Front wings with three post-triangular rows to the level of the nodus ; hind 
wings with three or more rows of cells between the proximal subbasal 
sector (A; of C. & N.) and the Aind margin, rarely with any single post- 
triangular cells reaching across the entire width of the field from short 
sector to first sector of the triangle. 
B. Abdomen stout (e. g. segments 4-6 each twice or less than twice as long 
as wide), not, or but little, narrower in dorsal view at segment 4 than at 
segment 2. | 
C. Hind wings uncoloured or faintly yellow at extreme base in some 
females. Face, thorax, and abdomen bright green (dull yellowish in 
young), the abdomen marked with black ; thorax and abdomen of old 
males pruinose. 
D. Younger males and the females with a large quadrate black median 
dorsal spot on each of abdominal segments 4-9, 8 and 9 often 
* Orbigny’s Voy. dans ’Amér. Mérid. vi. part 1, p. 217 (1848). 
+ Handb. Ent. ii. p. 856 (1839) ; Calvert, Trans. Amer. Ent. Soc. xxv. p. 78 (1898). 
