The Descent of Man

ent as talc, surrounded by nervures, and called
the speculum. In Ephippiger vitium, a member
of this same family, we have a curious subordinate
modification; for the wing-covers are greatly
reduced in size, but "the posterior part of
the pro-thorax is elevated into a kind of dome
over the wing-covers, and which has probably
the effect of increasing the sound." (37. Westwood
'Modern Classification of Insects,' vol. i.
p. 453.)
We thus see that the musical apparatus is more
differentiated or specialised in the Locustidae
(which include, I believe, the most powerful
performers in the Order), than in the Achetidae,
in which both wing-covers have the same structure
and the same function. (38. Landois,
'Zeitschrift fur wissenschaft Zoolog.' B. xvii.
1867, ss. 121, 122.) Landois, however, detected
in one of the Locustidae, namely in Decticus, a
short and narrow row of small teeth, mere rudiments,
on the inferior surface of the right