PACHYDIPLAX. 34] 
Soc, xx. p. 225 (1893) ; 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). 
There is but one known species. 
1. Pachydiplax longipennis. 
Libellula longipennis, Burmeister, Handb. Ent, ii. p. 850 (1839); Calvert, Trans. Amer. Ent. Soc. 
Xxv. p. 66 (1898) %. 
Mesothemis longipennis, Hagen, Syn. Neur. N. Amer. p. 173 (1861)*; Proc. Bost. Soc. Nat. Hist. 
xviii. p. 78 (1875)*; in J. M. Jones’s Visitors’ Guide to Bermuda (1876) * (teste Verrill *’) ; 
Uhler, in Heilprin’s The Bermuda Is. p. 154 (1889) °. 
Dythemis longipennis, Uhler, Sci. Res. Chesapeake Zool. Lab. J. Hopk. Univ. 1878, p. 33”. 
Pachydiplax longipennis, Calvert, Trans. Amer. Ent. Soc. xx. p. 265 (1893)*; Occas. Papers, 
Bost. Soc. Nat. Hist. vii. 6, p. 42 (1905) °; Kellicott, Canad. Ent. xxvi. p. 347 (1894) *°; Odon. 
Ohio, p. 114 (1899) *'; Williamson, 24th Rep. Geol. Indiana, p, 326 (1900) ”; Needham, 
Bull. 47 N. Y. St. Mus. pp. 526, 527 (nymph) (1901); Proc. U.S. Nat. Mus. xxvi. t. xlvii. 
fig. 1 (venation) (1903) **; Howard, Insect Book, t. xl. fig. 9 (¢ color.), t. xlv. fig. 7 ( ¢ ) 
(1901) °; Verrill, Trans. Conn. Acad. Arts & Sci. xi. pt. ii. p. 816 (1901-02) *; Blatchley, 
A Nature Wooing, p. 215 (1902) ‘"; Walker, Canad. Ent. xxxviii. p. 153 (1906) **. 
Libellula socia, Rambur, Névr. p. 96 (1842) **. 
A few other older references are cited by Hagen *, and there are some of later date confirming, but not adding 
to, our information on the distribution. 
The majority of the Mexican specimens before me show two differences from those from the United States, 
viz. (a) that the wings of the males, although sometimes smoky, exhibit none of the brownish-yellow so 
frequently seen between nodus and stigma; (0) the hind wings of the females have the two dark basal 
streaks, or at least that in the subcostal space, as in the males. Five females (San Pedro, Guadalajara, 
Mexico City) are like all those of the United States which I have seen in lacking these streaks (cf. 3°"), 
but the difference is not due to age. 
Fifteen males, fifteen females from Mexico City (4 ¢, 15 9 by Mr. Deam, July 1, 1900; 3 ¢ June 24,1897, 
by Mr. Barrett; the remaining 8 ¢ by Messrs. Smith and Schumann not dated) give the following 
measurements, &c.:—Abdomen, ¢ 23-26, average 246; 2 22-24, aver. 266 mm. Hind wing, 
S$ 29-33, aver. 30°5; 2 29-32°5, aver. 30°2 mm. Front wing: ¢ 9, antecubitals 6-7 (6), postcubitals 
5-7 (6). Hind wing: antecubitals, ¢ 9 5-6 (5); postcubitals, g 6-7 (6), 2 5-7 (6). 
The range of size for the species as a whole*" is: Abdomen, ¢ 20-29 (Texas); 9 18-25. Hind wing, 
3 23-345 (Texas); 9 25-32°5 (Mexico City) mm. The amount of variation in size which may exist in 
the same locality at the same time is shown by measurements from three males taken at Thomasville, 
Georgia, June 6, 1903, viz. abdomen 22-26, hind wing 25-33 mm. 
Hab. Canapa. Ontario}8, Victoria 4 in British Columbia; Unitep States, east of the 
Rocky Mts.?47~-13 from Manchester (Miss Wadsworth, coll. ejusd.: 1 2) in Maine, 
Massachusetts 4, Michigan !°, and Montana* southward, Yellowstone 4, Olympia in. 
Washington (Kincaid, coll. P. P.C.: 1 3), North California 3; Lower CatiFrornia, San 
José del Cabo (Eisen, coll. Calif. Acad. Sci.: 1 2 *).—Mexico![3 6,12 ], Matamoros 3, 
San Pedro (Calvert, coll. P. P. C.: 1 2) in Coahuila, Guadalajara [1 9 | (Schumann), 
El Castillo [McClendon] and Ocotlan (Calvert, coll. P. P. C.: 3 2) in Jalisco, 
* This specimen, and consequently the species, was overlooked in the preparation of my paper in Proc, 
Calif. Acad. Sci. (2) iv. pp. 463-558 (1895). - 
BIOL. CENTR.-AMER., Neuropt., Judy 1907. 9 y 
