144 NATURAL FERTILISATION 



until the publication in the present year of Prof. Miiller's book 

 already mentioned, to the corresponding adaptations of the 

 structure of insects for the same purpose. This naturalist 

 an accomplished entomologist as well as botanist has made 

 this branch of the subject his special study, and has collected 

 together a large number of interesting and curious facts. 



Pollen removed by Insects in two ways. 



There are two ways in which insects perform their part in 

 fertilisation in their search for honey and for pollen. Several 

 instances occur of the mode in which insects, especially those 

 furnished with a long proboscis and belonging to the orders 

 Lepidoptera and Hymenoptera, involuntarily detach some of the 

 pollen while obtaining their food, and carry it away with them 

 to fructify other flowers which they then visit. One of the 

 most interesting examples of this was first described in detail 

 by Darwin in his work on the 'Fertilisation of Orchids;' and it 

 is extremely easy to observe the manner in which the pollen- 

 masses or " pollinia " of Orchids are carried away on the pro- 

 boscis t)f butterflies and moths. The natural order Asclepi- 

 adaceae, to which belong the beautiful waxen-flowered Hoya and 

 the singular foetid Stapelia, has the pollen arranged, in the 

 same manner as in Orchids, in pollen-masses which are similarly 

 fixed in pairs to a viscid base, the whole apparatus being easily 

 detached on to any insect which visits the flower. 



The second mode in which insects assist in the fertilisation 

 of flowers is by the voluntary deportation of pollen ; and this 

 is chiefly effected by Hymenoptera belonging to the class 

 Apidae, which includes the hive and bumble bees, that build 

 nests in which they store up large quantities of food for their 

 young while in the larva state. This "bee-bread," as it is 

 termed, with which the thighs of homeward-bound bees are 

 seen to be heavily laden, consists almost entirely of innumer- 

 able pollen-grains robbed from the flowers, which the little 

 depredators may be seen to despoil in a very scientific manner. 

 Though the greater quantity of this pollen is carried home, 

 small quantities of it are unintentionally left behind here and 

 there on the stigmas of the flowers, quite sufficient to insure 

 the fertilisation of the ovules. Prof. Miiller arranges the 

 different genera of Apidae into a series according to their 

 adaptation for this deportation of pollen, from the extent to 

 which their thighs, shins, and feet are clothed with hairs. 



Besides these, there is a third purpose for which insects 



