I50 



INTRODUCTION 



trace of feathery branching. The abdominal collecting-apparatus of one division of 

 the bee family stands in sharp contrast to the collecting-apparatus developed on the 

 hind-legs of the other division, not only in the structure of its hairs, but also in 

 the way it is used. The pollen-collecting apparatus of the latter consists of a forest 

 of feathery hairs, into which the tarsal brushes (formed of simple stiif bristles) sweep 

 the pollen they have scraped off. In the present group, on the other hand, 

 the pollen-collecting apparatus is a large brush of simple rigid bristles, and this 

 itself sweeps up the pollen. That this difference of function, to which the difference 

 of structure points, actually exists, is thoroughly confirmed by observing the visits 

 which the dasygastres make to flowers. For more than nine-tenths of the flowers visited 

 by bees with abdominal brushes are such as are adapted to dust the ventral surface 

 of the bee with pollen (Echium, Papilionaceae, Compositae, and so forth), so that the 

 ventral collecting-apparatus is frequently completely filled with pollen without any 

 help from the tarsal brushes. On the heads of Composites, for example, dasygastres 

 may be seen rapidly thrusting their tongues into one floret after another for the 

 purpose of getting nectar, meanwhile turning the body half or entirely round, so that 

 the pollen lying loose on the surface of the head is forced between the hairs of the 

 abdominal brush. This is quite full after a few heads have been visited. In this 



way Hermann Miiller very frequently saw, for 

 example, Megachile lagopoda L. upon Onopordon 

 Acanthium, and Osmia spinulosa K. upon Car- 

 duus acanthoides. More rarely bees of this 

 group gather pollen on flowers which deposit 

 it on their backs. In such cases they use their 

 tarsal brushes to remove pollen that remains 

 sticking among the feathery hairs that cover 

 their bodies, and bring it to the abdominal brush. 

 Hermann Miiller saw, for example, Anthidium 

 manicatum Z. behaving in this way on the 

 flowers of Ballota nigra. 

 The abdominal collecting-apparatus is similarly formed in bees belonging to 

 different genera, while, as shown above, the collecting-apparatus on the hind-legs 

 exhibits gradual specialization, step by step, from Prosopis to Apis. It is also 

 possible to recognize a series of adaptations in the mouth-parts having reference to 

 getting nectar from flowers. Hermann IMiiller describes these ('Fertilisation,' pp. 48- 

 64) somewhat as follows: 



When at rest (Fig. 64, i) the lower mouth-parts, i.e. maxillae and labium 

 (under lip), are withdrav/n in Prosopis into a cavity on the under-side of the head, 

 which they exactly fill, and this is effected by means of the folding together of stiff 

 chitinous parts, which are united by movable joints. The two basal pieces or 

 cardines of the maxillae (Fig. 64, 4, cc) are jointed into two sockets at the sides of 

 the cavity under the head, in such a way that they can rotate either forwards or 

 backwards. When at rest they are folded back, drawing with them the stipites 

 (stems) of the maxillae (Fig. 64, i, 2, 3, 4, st), which are movably articulated to 

 their distal ends, and also the mentum {nit), which is fastened between them, the 

 result being that they are completely covered by these structures. The laciniae of 



Fig. 63. Abdominal collecting-apparaius 

 (after Herni. Miiller). (i) Abdomen of Osmia 

 spinulosa A"., seen from below. (2) Side view 

 of the same ( X 7). 



