1971] 
Alcock — Behavior of Stinkbug 
225 
as its partner. It is in this position that insertion of the aedaegus 
occurs. Usually the male then turns, dismounts and faces away 
from the female. Copulation proceeds in this end-to-end pose. This 
is a very common sequence of events among the Heteroptera in gen- 
eral (Grasse, 1951; Weber, 1930). E. conspersus is then the only 
stinkbug known to omit the male-above position and to effect a 
copulatory union directly end-to-end. 
How might such behavior have evolved? Weber noted (i93°> 
p. 307) that there were only two basic patterns of Hemipteran copu- 
lation — ( 1 ) the male and female facing in the same direction with 
the male by the side or above the female and (2) the male and female 
united end-to-end facing away from each other. At the time no species 
was known which copulated in position (2) without first assuming 
the side-by-side or male-above position. From this evidence Weber 
argued that the end-to-end position was an elaboration of the pre- 
sumably more primitive position ( 1 ) . Therefore it seems reasonable 
that the unusual courtship pattern of E. conspersus which omits the 
male-above component altogether is probably a relatively recent evolu- 
tionary invention derived from the second basic pattern. Representa- 
tives of all three copulatory patterns occur in the Orthoptera (and 
doubtless other insect orders); Alexander’s (1964) explanation for 
the evolution of direct end-to-end initiation of copulation in the 
Orthoptera is essentially the same as that outlined above for the 
Hemiptera. 
Omission of the back-climbing phase of courtship makes some sense 
for pentatomids given their bulky flattened shape which could make 
coupling awkward in a male above/female below position (N. T. 
Davis, pers. comm.). Indeed in type (2) copulations the function of 
the male’s dismounting and turning away from the female may be 
to achieve a more stable and easily maintained copulatory position. 
Initiation of copulation directly in the end-to-end position might 
have had its origin in premature turning behavior. After a number 
of unsuccessful attempts to copulate while on the back of a female, 
some males might tend to dismount and turn despite the fact that 
coupling had not yet taken place. Teyrovsky (1949) observed a male 
D. baccarum attempt a direct end-to-end union with another male it 
had been unsuccessfully courting. Presumably in the evolution of 
the sexual behavior of E. conspersus selection first favored males with 
a low threshold for dismounting and turning. Gradually selection 
has eliminated mounting the female entirely while favoring those 
males which act to induce the female to assume that position which 
makes direct end-to-end mating most easy. 
