214 On Aquatic Carnworous Coleoptera or Dytiscide. 
from the air on account of their completely subterranean existence ; we may 
therefore conclude that it is under the influence of much exposure to the atmosphere 
that the sensitive pubescence on the antennz of beetles has been developed. The 
more elongate exserted setze present in the Carabidze but absent in the Dytiscidze 
have probably a totally different function from the fine sensitive pubescence ; it is 
quite possible that they are tactile organs similar to the whiskers of the cat, and 
that they are absent in the Dytiscidee because the resistance of the water when the 
insect is active would move the setze, and, if they are as I have supposed sensitive 
to pressure, render them a nuisance to their possessor. Thestudy of these 
structures falls however to the Carabophilist, but I must remark in connexion 
with the question of the relations between the Carabidze and Dytiscide, that in the 
former family there exists considerable differences in the clothing of the antenne ; 
thus im the rare and anomalous Trachypachys there is a complex and symmetrical 
system of antennal setze, but sensitive pubescence seems to be entirely absent ; 
while in other cases, as in Anthia, there is a beautiful development of the 
sensitive pubescence and a nearly complete absence of sete. In the Scaritidee and 
Broscidee the four basal joints of the antennz are glabrous (except that in some 
Broscidee porosity begins at the apex of the fourth joint) but on the other joints the 
rule is that the porosity is confined to the edges of the more or less compressed 
joints, the flattened sides being glabrous. Exceptions occur in which the porosity 
covers the whole of these joints, and there are other exceptions -these much more 
remarkable—in which the porosity is almost entirely absent. It is especially 
noteworthy that the forms presenting this latter peculiarity are those which from 
their form and appearance, are probably most completely subterranean in their 
habits, such as Monocentrum, ‘Teratidium, Neocarenum, Passalidius, and 
Metaglymma. In Passalidius there are neither punctures nor hairs, but there are 
grooves on the edges of the joints. In Neocarenum there exists scarcely any 
pubescence but a few coarse punctures. In Scarites excavatus there are large 
punctures mixed with the fine porosity on the edges of the joints. Thus we see 
that in the subterranean Carabidze, where the antennze are less subject to atmos- 
pheric influences than the other members of the family, the antennee have their 
sensitive structures less largely developed than usual, and that in the most completely 
subterranean forms of the family the antennz approximate to those of the aquatic 
Dytiscidze, without however being so completely simple as in the water beetles.* 
*Tam greatly indebted to Mr. H. W. Bates for furnishing to me the information above recorded 
about the sensitive structures of the antennz in the Scaritini and Broscini. Mr. Bates has examined 
many species in the following genera with the results thus tabulated—Carenum, Pasimachus 
Emydopterus, Euryscaphus, Carenidium, Oxylobus, Scaraphites, Crepidopterus; in the above the 
compressed joints 4-11 are glabrous only along the middle of the flattened sides ; while in Monocentrum, 
Teratidium, Neocarenum, Passalidius, Metaglymma, Brullea, the antenne haye a diminished band of 
porosity on the edges or are entirely smooth ; in Scarites they are much as in Carenum but more, 
variable ; in Gnathoxys there are rather distant pores, and in Percosoma there is dense porosity. 
