part u.]| THE INSECTS WHICH VISIT FLOWERS. 63 
folding movements which its suction apparatus is capable of 
into play simultaneously. It draws back the base of the tongue 
into the hollow end of the mentum (as in Fig. 20); folds the 
tongue, together with the inclosing laminz and labial palps, 
downwards and backwards (Fig. 20 shows this action beginning), 
draws the retractors (z) backwards (half completed in Fig. 20), 
and rotates the cardines ¢ (which in the figure are still directed 
obliquely forwards), backwards ; the whole apparatus is thus folded 
together, and lodged in the eavity below the head, completely 
filling it (Fig. 21, 1). 
# i, 
Fic. 20.—Sucking apparatus of Bombus silvarum, L., half folded up. Side view. 
The outer wall of the hollow end of the mentum is broken away to show the involution of the 
lowest piece of the tongue, a abe. 
Letters as in Fig. 18,—except: a, base of tongue; 6b, angle of fold; abc, part of tongue folded 
in mentum, 
When the hive-bees and humble-bees were declared to be the 
most important of all insects in the fertilisation of our native 
flowers, this assertion applied only to the individuals concerned 
- in the care of the young, z.e. the workers among the hive-bees, 
and the females and workers among the humble-bees. 
In all species which provide for their own young, the males are 
of much less use in fertilising plants than the females, as they only 
look after their own maintenance, and accordingly neither collect 
pollen nor visit flowers very diligently. Yet in all species in 
