512 EXTERNAL ANATOMY OF INSECTS. 



just above the base of the antenna : a circular process 

 forms the torulus in Fulgora and others. It is also often 

 placed in a cavity of the front, as in several wild-bees, 

 Melitta K., and in Locusta Leach on the sides of an ele- 

 vation of that part a . In a large majority of insects the 

 bulb {Bulbus) or ball which is received by the bed, wears 

 the appearance, especially in the Hymenoptera, of a di- 

 stinct joint; but if you carefully examine it, you will 

 clearly see that it is merely the base of the scape swelled 

 out into a spherical or other kindred form b ; and often 

 marked, as in the Cicindelida, with impressed points : 

 as it is the piece by which the antenna moves in its soc- 

 ket, this form of a rotula was doubtless given for its more 

 ready motion in all directions. This structure is princi- 

 pally conspicuous in the Coleoptera and Hymenoptera 

 Orders : in the others the base is not so distinguished 

 from the rest of the scape. If you carefully extract the 

 antennas of a beetle, say a Copris or Lamia, and examine 

 its base or bottom, you will find that it is open for 

 the transmission of muscles and nerves ; that in its up- 

 per margin it has a deep notch or sinus, on each side of 

 which is a smaller notch ; and that all round the margin, 

 which is very lubricous, a membranous ligament is at- 

 tached, by which it was affixed in the torulus. Its arti- 

 culation, therefore, seems of a mixed kind, like that of 

 most other organs and parts of insects, partaking of the 

 ligamentous, ginglymous, and ball and socket. In the 



a Plate VI. Fig. 4. c. i'. 



b Plate XII. Fig. 9. 1". This circumstance was very recently 

 discovered ; which will account for this plate not being quite correct 

 in this respect, the bulb being represented as a distinct joint in 

 Fig. 6, 10, 26. 



