SENSATION IN INSECTS. 497 
that which leads to the conclusion that they possess keen 
powers of vision, smell, and touch. 
Pain.—Evidence of a satisfactory kind indicates that pain is 
by no means a phenomenon commonly exhibited by the lower 
forms of life in any high degree; indeed, even in the human race 
susceptibility to pain is far more developed in the higher than 
in the lower races of mankind; and the comparative indiffer- 
ence to pain exhibited by some races of savages is notorious. 
Dominant Sensations—Just as in man the sense of sight, in 
dogs that of smell, and in the timid herbivora the sense of 
hearing are the most important, so there are insects in which 
each of these senses is dominant over the others. I have 
already drawn attention to the remarks of Forel on this subject 
(p. 11). In the Dragonflies, Libellula, and the Diurnal Lepi- 
doptera, the sense of sight is undoubtedly paramount; the rapid 
hawking flight of the former is well known, and indicates the 
keenest vision, and Belt (naturalist in Nicaragua, p. 108) gives 
an instance of the manner in which some butterflies avoid the 
webs of spiders indicative of highly developed visual powers. 
He says: 
‘A large spider (Nephila) builds strong yellow silken webs, 
joined one to the other, so as to make a complete curtain of 
web, in which were entangled many large butterflies, generally 
forest species, caught flying across the clearing. I was at first 
surprised to find that the kinds that frequent open places were 
not caught, although they abounded on low white-flowering 
shrubs close to the webs; but on getting behind them, and 
trying to frighten them within the silken curtain, their instinct 
taught them to avoid it, for, although startled, they threaded 
their way through open spaces between the webs with the 
greatest ease.’ 
Hearing a Warning Sense.—In mammals, hearing is frequently 
a warning sense, more especially amongst those species which 
are helpless against their enemies. According to Graber, the 
Cockroach (Blatta Germanica) is exceedingly sensitive to sounds, 
especially in the dark, or when its eyes have been blinded. It 
is familiar to all that children and timid persons are easily 
