1 INTRODUCTION Il 
The tongue (Fig. 25, p. 145), using the term in 
its wider sense, is a complex structure consisting of 
an outer and an inner pair of sheaths, the maxillae 
and the labial palpi, which enclose the true tongue, 
this being in the humble-bee and its allies a long 
hairy organ having a groove on its under side. The 
honey is sucked up by the dilatation and contraction 
of the groove and of the tube made by the sheaths 
around the tongue. When not in use the whole 
apparatus is neatly folded away under the head. 
Humble-bees breathe, not as we do through 
openings in the head, but through’ small holes in 
the sides of the body, called spiracles, of which 
there are two pairs in the thorax and five pairs (in 
the male six) in the abdomen. The spiracles of the 
thorax, which are situated under the wings, contain 
a vocal apparatus which is the source of the buzzing 
sound made by the humble-bee when it is irritated. 
Just inside the spiracle the windpipe is enlarged to 
form a sounding-box, and the sound is produced by 
the air expired passing over the edge of a curtain- 
like membrane fixed across the mouth of the sound- 
ing box. During the buzzing the wings, it is true, 
vibrate or quiver and increase the sound, but if they 
are removed the sound is still produced, while if 
the thoracic spiracles are covered, as Burmeister 
showed, the buzzing ceases or becomes so feeble 
that it is scarcely perceptible. 
Other organs will be considered as occasion 
arises. 
