part 11.) THE INSECTS WHICH VISIT FLOWERS. 61 
By now rotating the cardines (c) forwards, the whole suction- 
apparatus is carried forward by twice the length of the cardines. 
The retractors (zz) are now rotated forwards in their turn, and a 
further advance of twice their length is given to the mentum (mt) 
with its appendages, to the labial palps, and to the tongue, while 
the maxillz remain in their place, and their laminz now inclose 
only the mentum and the hinder part of the tongue. Finally, the 
basal part of the tongue contained within the hollow part of the 
mentum is projected forth, and the tip of the tongue now reaches 
its farthest extension (20 to 21 mm. from the mouth in Bombus 
| hortorwm), and dips again into the honey at the base of the flower. 
In flowers which contain abundant honey, a humble-bee may be 
seen to perform the act of sucking four or five, or sometimes even 
eight or ten times, the tip of the tongue being each time dipped 
into the honey, then drawn back into the sheath, and the sheath 
brought up to the mouth. 
(2.) To reach honey which lies less deeply, the bee need not 
rotate the retractors (2); the tongue therefore remains constantly 
insheathed by the laminz and labial palps, and only the basis of 
the tongue moves in and out of its cavity in the mentum, bringing 
its tip in and out of the extremity of the suctorial tube. 
(3.) When the bee flies from one flower to another, it carries the 
proboscis } extended, so as to introduce it in the act of alighting 
into the tube of the flower; but the tongue is concealed within its 
' sheath, to protect the delicate whorls of hairs, and to let the 
terminal joints of the labial palps perform their function of tactile 
organs. 
So in flying from flower to flower the base of the tongue is 
contained within the hollow of the mentum, and the retractors (2) 
are directed backwards, while the cardines may be directed down- 
wards (Fig. 19), forwards (Fig. 18, 2), or backwards, according to 
the depth of the flower which the bee has in view. 
clearly distinguished ; they were as described above. What went on between the 
chitinous plates of the laminz and labial palps was of course invisible, but when 
these parts were drawn aside, a progressive erection of the whorls from the tip of 
the tongue backwards, could sometimes be clearly seen. The fact that the basal part 
of the tongue, which gets drawn into the hollow of the mentum, is free from whorls, 
seemed to stand in accordance with this action. At the same time, special muscles 
for the erection of the whorls are not present ; and therefore my explanation becomes 
unsatisfactory. In several Brazilian bees, my brother Fritz Miiller has found that 
the hairs of the tongue are transformed into stalked scales, which seem hardly fitted 
to drive the honey mouthwards by erection. In an undescribed azure-blue Luglossa, 
the imbricated scales seem to form a tube round the tip of the tongue, so that here 
suction may perhaps go on, without the tip of the tongue being withdrawn into 
the sheath formed by the lamine and labial palps. 
1 The whole suctorial apparatus is thus designated for shortness’ sake. 
