12 AMERICAN HYMENOPTERA. 



positor in the female and distinct claspers — copulatory organs 

 — in the males, there is little difference between the two 

 sexes. 



Variation. 



Variation in color, venation and structure is noticeable 

 in some members of this tribe, and especially in the genera 

 Ophion, Enicospilus and Eremotylus. Here the color of the 

 body varies in some species from luteous to ferruginous, or 

 fuscous, and normally hyaline wings become tinged with 

 fulvous or fuscous, while — in Thyreodon — the amount of black 

 in the wings varies widely. The amount and strength of 

 areolation of the metathorax, the character of the radial vein 

 in Eremotylus, and that of the discocubital vein in Ophion 

 vary considerably ; the latter being in some species angularly 

 broken and appendiculate to arcuate. The size of the ocelli 

 has hitherto been considered constant and has been used as 

 a specific character, but some specimens of Athyreodon and 

 Thyreodon indicate that this is not entirely fixed. The num- 

 ber of frenal hooks has been used as a general specific char- 

 acter but varies considerably in a species, and often even on 

 the two wings of a specimen. 



So far as known there are no cases of mimicry in this 

 tribe, but Dr. Ashmead thought that " T. flammipennis 

 mimics some of the spider-killing wasps — Ceropalidas — so 

 common in its habitat." 



Abnormalities. 

 No records of abnormalities in this tribe have come to my 

 attention, but while studying the group I have found several 

 more or less abnormal specimens. One specimen of Eremo- 

 tylus macrurus in the Massachusetts Agricultural College col- 

 lection has an extra anterior wing on the left side, articu- 

 lated just in front of the normal anterior wing.* This extra 

 wing has the venation characteristic of the species and ap- 



* The specimen was so dried that in spreading the wings to bring 

 out the abnormality for exhibition the extra wing was broken off, but 

 Prof. C. H. and Dr. H. T. Fernald testify to the validity of this 

 abnormality. 



