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Psyche 
[December 
occur in certain species of the genera Aradus, Dysodius and 
Isodermus. 
Incidentally the term “arolium” is used in general insect 
morphology and in hemipteran taxonomy with several different 
meanings which urgently need elucidation. Crampton (1923) 
applies the name primarily to the undivided pad-like structure 
between the claws of Orthoptera, e. g. Periplaneta. Further he 
mentions that the arolium in certain Hymenoptera and Homo- 
tera may be partially divided or faintly marked off into two 
lateral portions. There is no reference in Crampton’s paper to 
the fact that in Heteroptera the arolium is always divided and in 
fact is referred to by taxonomists only in the plural. As illus- 
trative of the most exact use of the term in Hemipterology, 
figure 11 shows the arolia of a Mirid after Knight (1923). 
The same drawing shows also the pseudarolia which in many 
Mirids are greatly developed and perhaps take the place of 
the true arolia which are reduced to mere bristles. Knight’s 
arolia arise as shown in the figure truly between the claws and 
are probably homologous with the undivided arolium described 
by Crampton. But in Pentatomids, Coreids, some Aradids and 
in Termitaphididce, the present writer finds that the arolia do 
not arise between the claws, but each from the base of the corres- 
ponding claw as shown in figures 7, 9 and 12. In these families 
it would seem that the so-called arolia are really homologous with 
the pseudarolia of the Miridse, while the true Mirid arolia are 
represented by bristles between the claws as shown in the Pen- 
tatomid, Euschistus (fig. 12) and in a Termitaphid in Silvestri’s 
drawings. Organs evidently exactly homologous with the so- 
called arolia of Euschistus, Ctenoneurus and Termitaphis are des- 
cribed and figured in the Coreid, Anasa, by Tower (1913) as 
pulvilli. 
Whether the appendages figured in Termitataradus and in 
Ctenoneurus constitute true or pseudarolia or pulvilli does not 
affect the question of relationship since they are obviously homo- 
logous structures in the two genera. 
In 1920 Spooner for the first time recorded a peculiar con- 
dition in the Aradid head in which the rostral setae, instead of 
proceeding more or less directly cephalad and then caudad to 
