INSECT VISITORS 139 
while the ‘flasks’ occur in various parts on the distal joints. Such ‘flasks’ are 
found in Apis, Bombus, Eucera, Xylocopa, and Anthophora. The olfactory pits 
and olfactory cones vary greatly in number. In honey-bees there are 14,000 to 
15,000 pits, and some 200 cones on each antenna. 
Among Diptera there are chitinous pits containing sensory cones, and of 
very varied forms. The pits are sometimes simple, with only one cone; sometimes 
compound, with a larger number (up to 100) of cones. The Tipulidae possess 
isolated cones only, while both kinds are present in Tabanidae, Asilidae, Bomby- 
liidae, Leptidae, Dolichopodidae, and Stratiomyidae. In the other families there 
are only aggregated cones. In the flesh-flies and dung-flies there are 60 to 150 
pits, in Trypeta and others only 2 to 5 on each antenna. 
A few of the Neuroptera, Orthoptera, and Hemiptera also possess pits 
or sensory cones on the antenna. 
The centre of the olfactory sense of insects is to be sought at the base of 
the antennary nerve. At its point of origin occur peculiar rounded masses, the 
olfactory bodies, which are so described. 
As there is a well-developed sense of taste in many insects, it may be deduced 
that they also possess special gusf/afory organs, since in the case of odourless 
substances taste is only possible when these are touched 
by the mouth-parts of the insect, its seat must be in the 
region of the mouth. Sensory pits with nerve-endings 
are actually found (Kolbe, op. cit., pp. 442-5) both in 
the walls of the mouth-cavity as well as on the tongue 
and palps. These must at once come into contact with 
the food that is taken. On the proboscis of a fly, for 
example, organs of taste are found, together with tactile 
hairs. The interior of the tubular proboscis of a butterfly 
or moth is regularly beset with small chitinous cylinders, 
which project into its cavity, undertaking a quantitative TS 7" saps poe 
and qualitative examination of the fluid nourishment the tip of the ligula of Vespa 
taken in. At the base of the tongue in bees and similar pn cidset ) mip eaaG 
insects there are little chitinous pits on either side, which 
are regarded as gustatory organs. At the tip of the ligula and on the under-side 
of the first maxillae of some Hymenoptera (ants, wasps, bees) sense-organs (Fig. 56) 
are also present. The paraglossae of the honey-bee and humble-bees also possess 
similar taste-organs. 
It is a familiar fact that insects possess compound or faceled eyes, the peculiar 
structure of which is explained by their immobility and the slight power of move- 
ment possessed by the head. If insects were equipped with a single refractive 
apparatus like the eyes of a vertebrate, but immovable, this would need to be 
very strongly convex, and very prominent, to enable its owner to see at the same time 
objects in front and around. But such an arrangement would make distinct vision 
impossible on account of the well-known principle of spherical aberration. When 
eye and head are immovable, clear vision can only be attained by division of the 
eye into a number of radiating cones, capable of making isolated and independent 
observations, and so arranged that rays of light, from any object within the field 
