1933] Tropisms Effecting Copulation in the Bed Bug 119 
attempt, often, to copulate with others of their own sex. 
They even fail to differentiate between mature larvae and 
adults which are of approximate size and shape. The 
identical shape of the two sexes in the Japanese beetle, P. 
japonica, was also the reason for similar behavior in the 
case described above. The odor may have guided the males 
to the female ; however, upon coming in close contact with 
each other, they failed to discriminate between the two 
sexes. The male of the lady beetle, C. 9-punctata , previous 
to the act of mating, places the forelegs over the middle of 
the hemispherical body of the female and pivots over her, 
touching with his posterior legs and the tips of his ventrum 
the margins of the female. One observer relates how a 
male of the Scarabaeid species, Dynastes tityus L., having 
been permitted to crawl over his fingers, upon reaching 
the thumb, oriented himself upon the nail and attempted to 
insert his genitalia in the space between the nail and skin. 
One who is familiar with the size and shape of this beetle, 
and the similarity of the same to a thumb nail, will under- 
stand the cause of such a reaction. 
Reactions of such a nature were designated by early ob- 
servers as “stereotropic” — meaning reactions to solid ob- 
jects. This term, the writer believes, is not specific and he 
suggests the term “morphotaxis” for the particular kind of 
reaction discussed previously. This term is more suitable 
because it is the particular shape of the surface of the fe- 
male or her specific form which calls forth the definite 
orientation. Morphotaxis may be considered as a more 
specific division of stereotaxis. The general term “thig- 
motaxis,” substituting “stereotaxis,” the writer believes, is 
entirely inappropriate for this reason: Most, and perhaps 
all of the technical names of the various tropisms are based 
on the Greek name of the stimulus which causes the reaction 
and not on the name of the sense by which the stimulus is 
perceived. Thus the terms are “phototaxis” or “chemo- 
taxis” and not “optiotaxis” or “olfactotaxis.” Hence, why 
should “thigmotaxis”— orientation according to touch — 
substitute “stereotaxis” — reaction to solid objects? 
In the case with the above-mentioned Coleoptera, al- 
though the males manifested definite orientations with re- 
