354 OUTLINES OF EVOLUTIONARY BIOLOGY 



.ati 



at 



countries where they are plentiful this is perhaps the case. 

 They visit the flowers in order to collect both honey and pollen, 

 to be used as food for themselves and their offspring. The honey 

 is usually found at the bottom of a long narrow tube formed by 



the lower part of the corolla, 

 so that in order to reach it 

 the bee requires a corre- 

 spondingly long and narrow 

 instrument. This is pro- 

 vided in the shape of a very 

 complicated proboscis (Fig. 

 179), formed by modifica- 

 tion, especially elongation, 

 of certain of tha appendages 

 surrounding the mouth, 

 which in more primitive 

 insects, like the cockroach, 

 remain short and simple. 

 When not in use the pro- 

 boscis is neatly folded away 

 beneath the head, but when 

 a flower is visited it is un- 

 folded and inserted into the 

 tube containing the honey, 

 which is then drawn up into 

 the bee's stomach by means 

 of a special sucking ap- 

 paratus. In butterflies and 

 moths also a somewhat 

 similar proboscis is used for 

 the same purpose, but it 

 differs so much from that of 

 the bee in details of struc- 

 ture as to indicate that it has 

 been independently evolved 

 from the primitive mouth parts of some remote insect ancestor. 

 In both cases the mouth appendages have become specially adapted 

 for the very special purpose of sucking honey, and the necessity 

 for the fulfilment of the same function has led, as usual, to a 

 superficial resemblance between the two types of proboscis. We 

 have here, of course, another illustration of convergent evolution. 



FIG. 179. Head of a Bee, showing the com- 

 plex Proboscis formed from modified 

 Month Parts. (From Weismann's 

 " Evolution Theory.") 



at, antennae ; Au, large compound eye; au, 

 ocellus ; la., labrum or upper lip ; le, outer 

 division of second maxilla (paraglossa) ; li, 

 ligule or tongue, formed by fusion of inner 

 divisions of second maxil lee ; md, mandible ; 

 mx*t mx^, first and second maxillse ; pi, 

 labial palp; p.m., maxillary palp. 



