THE ENTOMOLOGIST. 491 



the broad base of the cone at its application to the terminal 

 membrane was -^-^ inch in diameter. Small as these organs 

 are, those of the terminal membrane of the antenna are still 

 more minute. The length of two of the longest of the minute 

 hairs measured 2 ^V 9 inch, and the diameter of the thickest of 

 the two was -3-5-^-0^ inch. The length of these hairs was 

 unequal, and they seemed to occur in pairs closely adjoining 

 each other. 



The optic and antennal nerves are the only ones that are 

 distinctly visible as passing from the cerebrum ; but there 

 appears rather indistinctly to be another pair beyond the 

 antennal ones that seem to pass from beneath the margin of 

 the fore part of the brain, and to proceed forward to the oral 

 organs of the insect, and are shortly lost sight of beneath the 

 muscles. 



The general distribution of the nerves in the body of the 

 insect cannot be traced in the specimen under consideration, 

 as the viscera and the muscular system completely obscures 

 them ; but in the limbs the course of the principal nerve and 

 the branches it gives off to the hairs on the surface of the limb 

 is frequently distinctly to be seen and traced, and especially so 

 in the large terminal joints of the fore limbs, with a linear power 

 of 320. There appears to be but one main nerve, which tra- 

 verses the whole length of the limb, and from which a branch is 

 given off to the base of each of the external hairs. There is no 

 enlargement of the branch at the point at which it departs 

 from the main nerve, but shortly before it reaches the base of 

 the hair it gradually enlarges and assumes the form of a bell- 

 shaped cone, the broad base of which is applied to the base 

 of the hair. The branches of the nerves thus appropriated to 

 the hairs are of extreme tenuity; the one belonging to the 

 hair with the large basal cone measured tttots inch iu 

 diameter ; the length of the cone at the base of the hair was 

 8T& inch and its basal diameter tt^it inch. Each hair 

 evidently has its especial nerve, but it is only under very 

 favourable circumstances that they can be so distincly traced, 

 as in the right forearm of the insect under consideration ; but 

 in far the greater number there are unmistakable indications 

 of their presence. 



The antennae are also furnished with hairs at the distal 

 portions of each joint. They are slender and few in number. 



