274 



SCIENCE. 



[Vol. xxn. 1^0. 563 



their character, I should like to know at what result the 

 philosophical observers have arrived. 



At first glance the organs might be supposed to be 

 auditory, on account of the membrane, which closes them, 

 and the only reason for rejecting such a supposition is 

 that I have not seen any trace of the staff-like rods or the 

 pyrif orm bodies which Graber found so well developed in 

 what could not be imagined to be anj'thing but organs of 

 hearing in the tibia of the locust, Locusta viridissima, and 

 of some other members of the same, or of an allied, order. 

 The auditory organs of our white ants seem to be in an 

 entirely different position and of an entirely different 

 structure. 



On the outer wall of the upper, or coxal, end of the 

 trochanter is a group of just seven conical, setose and 

 colorless hairs, surrounded by a circumvallate base, and 

 on the upper outer wall of the coxa is another group of 

 similar hairs, always ten in number, and, presumably, 

 having the same function. These groups are entirely 

 absent from the inner walls. To show its locality, the 

 cluster is exhibited on the trochanter by Fig. 10, and 

 greatly enlarged in Pig. 11. 



sides, and are sparingly scattered over the surface of the 

 tibiae. In Figs. 10 and 11 their general form and usual 

 position and arrangement are shown, although in these 

 particulars they are not constant. The number is also 

 uncertain within known limits, varying on the outer side 

 of each trochanter from thirteen to fifteen, thirteen being 

 the common number; on the femur two and on the upper 

 lateral wall of the tibia, from two to five, with sometimes 

 an unusually large subcentral one, similar to a large one 

 on the inner wall of each tibia; the inner walls of each 

 trochanter also bear from four to five; on the upper part 

 of the femur are from three to four; the central tibial 

 surface has one, and one is near the lateral border of the 

 distal extremity of the tibia. 



In structure they closely resemble the circular apertures 

 at the bases of the tibial spurs, each consisting of an ele- 

 vated ring, having, at the level of the general surface, a 

 delicate membrane furnished with a nerve-fibre, which 

 elevates the centre into a minute but conspicuous papilla. 

 These points are shown in Figs. .5 and 7, the latter being 

 an optical section of a pit. 



On the trochanters these organs are arranged somewhat 



77 ^^^^-^-^^^^^ 



EXPLANATION OF THE FIGURES. 



Fig. I, surface markings from the femur; Figs, 

 the general leg-surface; Fig. 7, optical section of a sensory pit; Fig. 



nd 3, from the tibiaj Fig. 4, from the tarsus; Fig. 5, sensory pit from the tibia; Fig. 6, sensory hair from 

 _ _ :nsory pit; Fig. 8, pilose depressions on the lower end of the tibial; Figs. 10 and 11, sensory hairs, pits 



and^'hooded pits on tlie trochanters; Fig. 12, tibial trachea, with recurrent branch; Fig. 13, position of supposed tibial auditory organ; Fig. i.^, pits on 

 the lower surface of the first and second segments of the tarsus, one filled with crystalline excretion; Fig. 15, sensory pit at the base of a tibial spur; 

 Fig. 16, tibial auditory organ, partly diagrammatic. All the figures are much enlarged. 



These hairs differ widely in size, form, and general 

 aspect from the sensory bristles of the general leg-surface. 

 Underlying them is a specialized group of nerve-cells, 

 which supplies each with a fine nerve-filament. 



It is a fact worthy of note that these and other sense- 

 organs are on the outer wall of the various parts of the 

 legs which bear them, and that they either have no repre- 

 sentatives on the surface toward the insect's body, or are 

 there smaller and in much less abundance. Even the 

 large sensory hairs of the general leg-surface are much 

 fewer on the inner aspect of the legs. 



In addition to these setose appendages, each trochanter 

 bears other sensory organs, which take the form of ele- 

 vated, circular, or oval rings, surrounding apertures of 

 the same form in the thickness of the walls, some being 

 capped by a conical, often oblique, hood-like membrane. 

 They, as usual, are found chiefly on the external walls of 

 the trochanters, but exist in fewer numbers on the inner 



in three groups, according to size, and the three or four 

 largest, resembling flat-topped papillsB pierced with a 

 central depression above the membrane, frequently be- 

 come confluent, those of the other two groups being 

 cajjped by a conical, often oblique, hood-like membrane, 

 as shown in Fig. 11. These hooded apertures bear some 

 resemblance to the "canoe-cells" of certain authors, and 

 which are said by Huxley to be only ordinarv pits over- 

 arched by a fine hair. In the present case, however, there 

 is no arching hair, but a distinct hood-like elevation, 

 which is especially conspicuous on the trochanters of the 

 soldier. 



It is reasonable to suppose that the capped depressions 

 have a function differing from that of the flat-topped 

 papillfe on the same surface. Those without the hooded 

 covering seem analogous to the sensory pits discovered on 

 the antennae of certain plant-lice by Dr. John B. Smith, of 

 Butger's College {Science, Jan. 20, 1893). A rather hasty 



