138 INTRODUCTION 
terminal ones, or scattered over the whole surface of the antennae, and consist 
of bristle-like or conical hairs, pits, and membranous canals. 
According to Kolbe (‘Einfiihrung in die Kenntnis der Insekten,’ pp. 432-5) 
the following are the facts with regard to the development of olfactory organs in 
the various orders of insects. 
Butterflies and Moths possess on their antennae projecting sensory hairs, 
simple chitinous pits with a single sensory cone, and also large pits with many 
SR b 
Fic. 54. Olfactory organs of Insects. a, Transverse section through the wall of the antenna of 
the Cockchafer. WV, nerve; Ch, chitinous membrane; G, ganglion-cell of the sensory cone (.S%) sunk in 
a pit. & Section through the antenna of Cetonia aurata. References asina. (After O. vom Rath.) 
such cones. The sensory hairs are large, pale, chitinous tubes, which are 
generally somewhat curved, and more or less tapering. The simple pits present 
a great variety in structure and are generally distributed, while the pits with many 
sensory cones are found only in certain genera. Hawk-moths possess the most 
specialized olfactory organs, and Kerner (cf. p. 125) has made observations with regard 
to the delicate sense of smell possessed by these insects. 
Upon the antennae of Beetles are to be found superficial sensory cones 
and sensory bristles, together with membranous canals and chitinous pits (Fig. 54). 
The number of these little sensory pits is par- 
ticularly large in carrion-loving beetles (Silpha, 
Necrophorous, Staphylinus, &c.). In the cock- 
chafer there are 39,000 such pits on the antennae 
of the male, and 35,000 on those of the female. 
No pits have hitherto been found in the Carabidae, 
Cerambycidae, Chrysomelidae, Curculionidae, 
and Cantharidae. 
Hymenoptera possess membranous canals, 
various forms of cone, and pointed sensory hairs 
Fic. 55. Olfactory organs of Gompho- (Fig. 55). Besides these structures, Forel has 
cerus rufus. Part of a longitudinal section , 
through the antenna. Cy, Chitinous mem- found ‘flasks’? and ‘champagne-cork organs 
OC caaglnn, Nonove (After Oven Rah, in the skin of Amfs, Humble-bees, and Bees. 
These also are of sensory nature. The ‘cham- 
pagne-cork organs’ of humble-bees and bees are confined to the terminal joint, 
1 [These structures were previously described by Hicks, ‘On the Organs of the Antennae of 
Insects,’ Trans, Linn. Soc., London, xxii, 1857.—TR.] 
