The Life of the Individual 99 



segments coalesce to form the adult head, the next three 

 the typical insect thorax, and the remaining ones, usually 

 twelve ' in number, fotm the abdomen. The thorax of the 

 adult bee is not typical, as will be explained later. 



Fate of parts of the embryo. 



Some of the head appendages of the embryo disappear 

 early, being rudimentary organs. For example, the append- 

 ages of the second segment become the antennae while those 

 of the third disappear in insects, but in Crustacea {e.g. 

 shrimps and lobsters) form the second antennae. Several 

 of the segments of the primitive insect head are not recog- 

 nizable in the bee. In the adult insect, these segments fuse 

 completely and by growth of various parts are so distorted 

 that an examination of the adult head does not suggest 

 segmentation and, without a study of the developmental 

 stages, this segmental origin would be unsuspected. 



The three thoracic segments are fused in the adult bee 

 but, since the three pairs of legs arise from them, the seg- 

 mental origin is suggested. The wings arise as secondary 

 outgrowths or appendages, dorsal to the legs, fron;i the two 

 posterior thoracic segments and do not correspond with 

 other appendages. In the adult bee, the first abdominal 

 segment is also fused with the true thoracic segments to 

 form the part known as the thorax, which therefore does 

 not correspond exactly with the thorax of lower orders of 

 insects. This fusion also occurs in most of the other Hy- 

 menoptera. The remaining posterior segments form the 

 abdomen of the adult but not all of the segments remain 

 visible to the outside. In the adult worker and queen bee, 

 the five posterior segments are turned in to form a pocket 

 aroimd the sting and anus. In the drone, only four segments 

 are so turned in. 



The embryo, just before leaving the egg, shows no rudi- 

 ments of antennae or legs, these temporarily disappearing. 



1 Two of these segments are obscure and in later stages there appear to 

 be present only ten. 



