368 



A third series of structures, which are perhaps to be 

 regarded as sense cells that serve the insect in maintaining 

 its equilibrium, is found in all the antennal joints, with the 

 exception of the first and last. On the proximal and distal 

 surfaces of the antennal segments the epidermal cells do not 

 chitinise, as they do on the general body surface, but, after 

 secreting a thick chitinous sheath, remain below and in close 

 contact with this, as large fleshy cells, which are especially 

 prominent in the angle between the lateral walls and the 

 distal surface (fig. 51). Each of these large cells has the 

 appearance of being binucleate; one of these nuclei is pro- 

 bably that of a mesodermal cell, the close adherence of the 

 ectodermal and the underlying mesodermal cell having already 

 been mentioned in connection with the cells of the tactile 

 bristles. In fortunate preparations a nerve may be seen 

 running to these large cells. I hope to discuss their function 

 more fully in a later paper. 



A fourth series of structures, which are perhaps to be 

 regarded as auditory organs, can be very clearly seen on the 

 last nine antennal joints. They are confined to the female, 

 and each structure is* in the form of a long, rather narrow, 

 hollow cylinder, sharply pointed distally, and formed of thin, 

 clear, transparent chitin (fig. 53). Immediately beneath 

 these hollow cylinders lies a mass of fleshy cells; sometimes 

 as many as five nuclei are visible, and no distinct cell walls 

 can be recognized. What is apparently a strand of nerve 

 fibres can occasionally be seen entering this cell mass. 



These organs are very prominent on the antenna of the 

 female, each being nearly as long as the antennal segment 

 bearing it, and frequently projecting in a sharp point beyond 

 it. The number in the several segments varies; the first and 

 second bear six each; the third has eight; the next three, ten; 

 the seventh, twelve; the eighth, fourteen; and the last, eight. 



Only the first (proximal) segment of the antenna is pro- 

 vided with muscles (fig. 11). These run longitudinally; dis- 

 tally they are inserted into the upper portion of the tip of 

 the first joint; then passing backwards, they diverge a little 

 and, entering the head, pass downwards, and become inserted 

 on the great cephalic phragmas. The lower portion of the 

 wall bounding the opening in the head through which the 

 nerves, muscles, and tracheae pass into the antenna serves as 

 a pulley on which the antennal muscles work. 



A second set of muscles is confined to the antenna ; it has 

 its origin along the posterior ventral half of the first joint 

 and is inserted into the upper part of the base of the second. 

 The function of this system is, obviously, to raise the greater 



