GOMPHOIDES. 153 
Dr. Karsch states* that the basal subcostal cross-vein is constantly lacking in 
Gomphoides and Aphylla, according to the material in the Museum fiir Naturkunde in 
Berlin. It is present in 93°/, of the front wings and 90°/, of the hind wings of fifty 
individuals which I have examined. | 
One feature of the females of Gomphoides requires special mention—the enlarged 
portion (“feuille” of de Selys) of the lateral margins of abdominal segments 8 and 9. 
Some species, e. g. G. suasa, were described as having “ bords des 8° et 9° non dilatés 
en feuilles.” On studying a number of females some with, others without, these 
enlarged margins, the former agreeing with the description of swasa, the latter differing 
only by these enlargements, it occurred to me that this difference might be connected 
with the act of oviposition. On relaxing a female with non-dilated margins, I found 
that I could easily spread out the segments in question so as to perfectly imitate those 
females which had been collected in the dilated condition. This experiment I have 
also been able to perform in the case of G. suasa pacifica. I note, moreover, that 
the chitin of the entire body is paler and softer, and therefore indicative of a more 
immature state, in the non-dilated females than in those which are dilated. I am 
certain that the apparent absence of dilated margins in a dried female is no proof that 
she was incapable of dilating them, and I strongly suspect that the dilatation is connected 
with the increase in the size of the egg-masses within the abdomen. The importance 
of these observations on the identification of females based on this character is self- 
evident, although the width of the enlarged portion differs in the various species f. 
Nearly thirty species of Gomphoides have been described, the genus ranging from 
Texas to Argentina. Most of the descriptions have been founded on a very few 
individuals, so that it is difficult, especially among the females, to determine whether 
various slight differences have a specific value, or are mere individual variations, or are 
due to age. For this reason the following synopsis will probably require much 
revision when more material is at hand. 
Synopsis of the Mexican and Central-American Species. 
Males. 
A. Inferior abdominal appendage very small, one-eighth or less as long as the 
superiors, often concealed within the posterior face of segment 10, entire or 
barely emarginated at tip; face more or less marked with brown. 
B. Abdominal segment 10 with no postero-inferior lateral projections, its 
posterior dorsal margin entire; 3~6 (in the adults) dark brown or black, 
* Ent. Nachr. xvi. p. 371 (1890). 
+ See on this subject the recent remarks of Dr. F. Ris, ‘Hamburger Magalhaensische Sammelreise,’ 
Odonaten, pp. 19, 20 (1904). 
+ Field-observations on the meaning of the differences, especially those of colour, employed in the synopsis 
of the species are very desirable. 
BIOL. CENTR.-AMER., Neuropt., June 1905. Xx 
