28 THE ANATOMY OF THE HONEY BEE. 



"V^Hien not in use the parts of the proboscis are bent back beneath 

 the head. By referring to figure 9B, giving a posterior view of the 

 head, it will be^-seen that the basal parts of both the maxillae (St) 

 and the labium (Mt) are susjiended in a large hollow on the back of 

 the cranium. This may be called the cavity or fossa of the proboscis 

 (PrhFs). Between the mandibles on the front of the head (fig. 

 9A) is a transverse movable flap, the lahnnn (Lw), attached to the 

 lower edge of the front wall of the head and constituting the upper 

 lip. The mouth (Mth) lies behind the labrum and the mandibles 

 close beneath it. 



Below the antennal sockets is a transverse, slightly arched suture 

 (a) which turns downward on each side and extends to the inner 

 angles of the bases of the mandibles. The area bounded by this 

 suture is the clypeus (Clp) and the suture itself may be called the 

 clypeal suture. 



On the posterior surface of the head (fig. 9B) is seen the pen- 

 tagonal foramen magnum (For) by means of which the cavity of 

 the head communicates with that of the thorax and through which 

 pass the nerves, oesophagus, blood vessel, and tracheal tubes. A 

 small rod (ten) inside the head arches transversely over the fora- 

 men magnum, cutting it into a dorsal and a ventral half. At each 

 side of the foramen is a large pit (c) which marks the base of an 

 internal chitinous beam of the head known as the mesocephalic pillar. 

 The opposite end of this pillar unites with the front wall of the 

 head on the clypeal suture below the antennae, where it produces 

 another smaller pit (h). 



Below the foramen magnum and separated from it by a wide trans- 

 verse bridge of the cranial wall is seen the large fossa of the proboscis 

 (fig. 9B, PrhFs) having the shape of an inverted U. The side w^alls 

 of this cavity are chitinous and from their upper edges are suspended 

 the maxillpe, wdiile the base of the labiinn is contained in the mem- 

 branous floor of the fossa. The base of the labium projects from the 

 head beneath or behind the mouth opening and its dorsal surface 

 forms the floor of a preoral cavity surrounded by the bases of the 

 mouth parts and labrum. 



It will be seen from the above description that the head wall of the 

 bee contains no suture except that bounding the clypeus and the one 

 which separates the labrum from the latter. Many of the 'higher 

 insects have the head w^all completely continuous, showing no di^'ision 

 at all into sclerites, but, in such forms as a grasshopper or cockroach, 

 and, in fact, most of the lower insects, the head as well as the other 

 parts of the body is made up of a number of plates. Hence this may 

 be regarded as the primitive condition, and it is presumed that the 

 head of the bee has been produced from one whose wall was divided 

 by sutures into a number of distinct parts. Therefore the different 



