116 
Psyche 
[Vol. 90 
The epiproctal shelf of a male played an important role during 
mating in T. alexanderae: the shelf and a female’s hindlegs on the 
substrate supported almost all of a female’s weight. A male’s epi- 
proctal shelf and the basal arms of the subgenital plate of a female 
are structures apparently functioning to distribute her weight 
because both structures are well-sclerotized and have large surface 
areas. 
The support given by the epiproctal shelf and the interlocking 
genitalia apparently increased the lateral stability of a mating pair. 
This can be adduced in the following observations. A mating pair 
had greater stability during copulation than when a male had 
backed fully beneath a female but before their genitalia had inter- 
locked. Also, it was difficult for a mating pair to fall over to one side 
when problems in stability occurred during copulation, although 
once they fell regaining a normal mating position was impossible. 
The stability supplied by the contact between the epiproctal shelf- 
subgenital plate and posterior abdominal sterna, the positioning of 
a female’s legs, and the interlocking genitalia probably also expe- 
dited the lifting of a female by a male, although the reason for the 
necessity of lifting a female is unknown. 
Acknowledgements 
I thank Dr. E. L. Mockford of Illinois State University, whose 
beneficial discussions about Psocoptera and review of the manu- 
script were greatly appreciated. 1. N. Holod and D. D. Pierce assisted 
in the production and the typing of the manuscript, respectively. 
Summary 
Pre- through postcopulatory behavior in Trichadenotecnum alex- 
anderae Sommerman is here quantified and discussed. Mating 
behavior follows a pattern described for many other species of Pso- 
coptera, in which a male approaches a female, fans his wings over 
his head, and backs underneath her without running over her dor- 
sum. Additional behavioral actions, including possible stridulation 
and antennal contact of a female by a male and a female assuming a 
receptive posture prior to mounting by a male, are believed to 
promote copulation. Evidence is presented for a sex-attractant 
pheromone produced by receptive females. 
