VII] THE SENSE ORGANS 153 



proximity, carries the nerve-ending. Such an organ is responsive 

 to waves of sound, and may be regarded as a very elementary 

 auditory organ. 



The extreme tip of the antenna was also found to be sensitive. 

 Here the chitin becomes very thin and delicate, forming a broad 

 funnel-like canal with a short hair placed on each side. This 

 seems to be an organ of touch. It is innervated by two or three 

 elongated bipolar cells. 



In the imago, the only sense-organs so far observed in the 

 antennae are tactile hairs and tympanulae. The hairs resemble 

 those of the larva, but are less numerous. The tympanulae were 

 discovered by Lespes [85]. A group of four, arranged in a line, 

 were found on the third joint in Sympetrum, and on the fifth joint 

 in Agrion. Lespes states that they contain statoliths, and are 

 convex in profile view. This suggests a balancing or orientating 

 function. Lespes also found, in Agrion only, on the third joint, 

 a peculiar tympanula closed by a stretched whitish membrane. 

 Possibly this is a feeble auditory organ. 



Experiments with Antennae. 



It has been often asserted that Dragonflies deprived of one or 

 both antennae are quite unable to direct their flight. In order 

 to test this assertion, I have several times taken into the field 

 with me a pair of fine dissecting scissors, with which I carefully 

 cut off one or both of the antennae of various Dragonflies captured. 

 I have treated in this way a number of specimens belonging to 

 the genera Hemicordulia, Anax, Aeschna, Ischnura, Austrolestes 

 and Synlestes. In no single instance did the operation affect the 

 insect in the least. Synlestes has the largest antennae of any 

 Dragonfly known to me ; yet the loss of them caused it no incon- 

 venience. While returning late one afternoon, I captured a 

 specimen of Anax, which, on examination, proved to be one whose 

 antennae I had removed in the morning. It was hawking about 

 in the ordinary manner. I can only suggest that it is not loss of 

 the antennae, but shock caused by damage to the nerve, if the 

 operation is clumsily done, that causes them any temporary 

 inconvenience. 



