498 THE SENSES AND SENSORY ORGANS. 
alarmed by unwonted sounds, especially in the dark, and the 
behaviour of Graber’s blinded cockroaches was indicative of 
fear whenever he produced sounds in their vicinity. Graber 
has also shown that water insects, both Coleoptera and 
Hemiptera, are readily alarmed by sounds. 
Lubbock has stated that Bees, Wasps, and Ants do not 
apparently take any notice of sounds, but he admits that there 
is evidence of their possessing the faculty of hearing. I am 
certain that the large Myrmecias of Australia are excited to 
take up a threatening attitude when a footfall is heard in the 
forest, and it appears probable that, in a country like England, 
where noises are continually occurring, that all but the most 
timid insects have probably long since learned to disregard 
them. In the virgin forest the stillness is often oppressive, even 
to man, and the slightest rustle amongst the foliage is very 
often more startling than the unexpected firing of a pistol is in 
a civilized country. 
It is only natural to conclude that insects which produce 
sounds also hear them, and that the grasshoppers and crickets 
take pleasure in their chirruping song; but it is possible also 
that the same sounds are pleasant to other insects. My friend 
R. T. Lewis writes to me that a large lace-winged fly in Natal, 
Notochrysa gigantea, is said to assemble in numbers round the 
head of a singing Cicada; it might be called the ‘audience 
insect, and he tells me that one which he sent me for ex- 
amination was caught with nine others flying round the head 
of one of these insect songsters. 
The Olfactory Sense—The fact that scents are keenly per- 
ceived by insects of certain species has been long known; the 
manner in’ which carrion-feeding insects discover a dead 
animal, and the discovery of a female moth enclosed in a chip 
box by numerous males of the same species, are well-known 
examples of a keen power of scent. Briefly, as Perris says [266], 
‘that this sense is highly developed in the greater number of 
Arthropods is a fact long ago established; for which there is 
no longer need of argument or proof.’ 
With regard to the localisation of the olfactory sense, how- 
