THE ANTENNJB. 91 



Section XIV. The Antenna. 

 PLATE VIII., Fios. 8 TO 13. 



The antenna consists of six joints, of which the third forms 

 the largest and most important part of the organ. 



The first joint (Plate VII., fig. 9) is an irregular ring with four stiff 

 setse in front at its distal margin. 



The second joint fits into the first and third. It consists of two parts. 

 The posterior (upper) is sub-conical, notched in front, and covered with 

 hairs, one of which on its outer side, is much longer than the rest. The 

 membrane uniting it to the first joint is rough, with exceedingly minute 

 hairs. The upper part of this piece fits into the cavity of the first joint 

 which partially conceals it. The anterior (lower) portion is an inverted 

 cone; its cavity opening posteriorly by a narrow ovate slit into the 

 cavity of the third joint. The integument is reflected back from the 

 margin of this slit to the base of the cone, and this reflection forms part of 

 the wall of the third joint. The external surface of the cone, and that of 

 the integument reflected back upon it, is covered with numerous minute 

 crenated plicae, directed backwards, not more than 1 -3000th of an inch in 

 breadth, and 1 -6000th of an inch in length their use is unknown. 



The third joint (Plate VIII., fig. 8) is elongated and ovate. 

 Its surface is covered with minute hairs, between which are 

 a vast number of pellucid dots, about 17,000 or 18,000 on each 

 antenna, with about 80 large irregular spots, of a similar 

 character, along the inner edge of the joint.* 



The smaller dots (Plate VIII., tig. 12) are about l-5000th 

 of an inch in diameter, or less. They consist of minute sacculi 

 opening on the surface, by an extremely small pore, not more 

 than l-8000th or l-10,000th of an inch in diameter. 



* First described by Dr. Braxton Hicks, Linn. soc. trans., Vol. 22. My 

 calculations confirm their number according to the same author. 



