58 THE FERTILISATION OF FLOWERS. [PART IT. 
chitinous plates surrounding the tongue, while their terminal parts, 
still acting as tactile organs, retain their original form, their short- 
ness, and their free position. The maxillary palps, originally six- 
jointed, get handed down as useless heirlooms, and show all stages 
of abortion from six joints to none. | 
A final increase in the length of the tongue over that of the 
organs which insheathe it is got by making the proximal part of 
the tongue coil twice round-and be retracted into the hollow end 
of the mentum; so that the tongue, which in the retracted state 
reaches quite to the end of its sheath, may be protruded by about the 
whole length of the sheath beyond it. As subordinate adaptations 
in the suctorial mechanism of bees, we have sharpening of the ends 
of the laminz to pierce succulent tissues, and the development of 
a membranous lobe at the end of the tongue. In the less 
specialised bees, the tongue is supported throughout its whole 
length by a chitinous ridge; this in the higher forms becomes 
a capillary tube which opens out into the spoon-shaped hollow of 
the terminal lobe. As soon as the terminal lobe reaches the 
honey, a little honey ascends the capillary tube to the taste- 
organs, and the bee may judge at once whether to continue 
sucking or not.’ : 
To follow out in detail the increasing complexity of the mouth 
in bees, through all its stages, would be a work of special ento- 
mological interest, as profitable as it would be comprehensive. 
Having studied the first adaptations to a floral diet in Sphecodes, 
Andrena and Halictus, we must pass over the manifold inter- 
mediate forms,? and investigate the complex mechanism of the 
mouth in the most specialised bees. I select for illustration the. 
mouth of those bees which of all insects play by far the most 
important part in fertilising our indigenous flowers; viz. humble- 
bees (Bombus) and the hive-bee (Apis). 
When we see the mouth-parts of these bees fully extended and 
artificially separated (Fig. 18, 1 and 2), it seems at first sight 
hardly possible that a suctorial apparatus so large and complex, 
which many times exceeds the head in length, can be as com- 
pletely received into a cavity below the head as it is in the least 
specialised bees ; yet this takes place by help of the four folding 
1 Wolff, Das Riechorgan der Biene, 1874; Hermann Miiller, Wechselbezichwngen, 
p. 30. In the German edition of this book, 1873, the lobe is said to be employed 
probably in licking flat surfaces of honey, 
* Some of these intermediate forms are figured in my essay, ‘‘Anwendung der 
Darwin’schen Lehre auf Bienen” (Verhandl. des naturhist. Vereins fiir pr. Rhein- 
land und Westfalen, 1872). 
