November 17, 1893.] 



SCIENCE. 



275 



examination of the antennse of the white ants does not 

 reveal pits of any kind on the surface, although I am not 

 prepared to say that they are not there. Dr. Smith also 

 found on the posterior tibiiB of the plant-lice a series of 

 the pits, exactly similar in structure, he says, to those of 

 the antennae in the male. Their function in Tennes fiavipes 

 is as problematical, as Dr. Smith remarks in reference to 

 the sensory pits of the plant-lice. They are present in 

 both the workers and in the soldiers of the white ants, 

 varying in the latter as they vary in the workers. 



Perhaps the most interesting of these sense-organs, by 

 reason of their position and of their probable character, 

 are certain depressed spaces, several of which are on the 

 tibife, and one on each of the first two segments of the 

 tarsus, where the parts come in contact with the surface 

 over which the insect may walk. With every step taken, 

 these sense-organs perform their work, and probably leave 

 on the surface walked over traces of the presence of their 

 owners, as may readily be imagined, to impress the senses 

 of those that follow. In all this remarkable collection of 

 sense-organs there is none that seems to explain so clearly 

 its reason for being as do these. Yet my supposition that 

 they leave some special evidence of their owners' former 

 presence which shall be manifest to the other members of 

 the insect community, is based upon the observation of 

 appearances in the tarsal organs of some individual Termes 

 which are not apparent in those of others. This is that 

 the deep depressions always present on the first and sec- 

 ond segments of the tarsus are sometimes filled with a 

 crystalline mass, which projects beyond the general sur- 

 face as a hemispherical protuberance, especially, as it now 

 seems, late in the season, and with presumably old sub- 

 jects, thus suggesting the idea that the tarsal organs, at 

 least, are glandular in function, and that the crystalline 

 substance is the hardened secretion collected through ab- 

 normal, or sluggish, action of the parts. 



On the tibiae the organs referred to are shallow depres- 

 sions in the wall, bordered by thickened margins, and 

 with the plane surface of the shallow studded with deli- 

 cate, exceedingly minute hairs, whose tips project slightly 

 beyond the general level, and necessarily come in contact 

 with any surface over which the insect may walk. The 

 tibial depressions, while they are always present, are not 

 always of the same outlines or of the same number. In 

 some instances there may be one large depression with 

 several small ones scattered about, as in Fig. 8, or the 

 single large depression may be divided into several smaller 

 portions, which shall be scattered over the region without 

 any regularity of arrangement. 



On the first and second segments of the tarsus the 

 organs are always present, and always in the same position 

 on the surface which must come in contact with the ground. 

 Each of the two segments bears one in the form of a thick- 

 walled, deep, hemispherical pit, the smooth inner surfaces 

 of which are also studded with fine hairs similar in appear- 

 ance to those of the tibial depressions, and with presumably 

 the same functions. It is these hollows that are in manv 

 specimens choked with the crystalline excretion already 

 referred to, and shown in Fig. 14, where one pit is filled 

 and the other apparently in its normal condition. Each 

 is plentifully supplied with fine nerve-fibres. Not rarelv 

 there are two pits, instead of one, on one or the other of 

 th« two segments; in a single instance, I have seen three 

 on the second joint. But these hairy hollows deserve more 

 extended investigation by some microscopist that may be 

 more conveniently situated for that work than I am, and 

 that may have the resources of a laboratory at his disposal. 



To such an investigator, thus fortunately situated, the 

 internal structure of these remarkable legs will also offer 

 important subjects for examination. This is especially 

 true of what I suppose, for reasons to be mentioned here- 



after, to be the insects' auditory organs, one being present 

 in each tibia, a supply of internal ears that would seem to 

 be more burdensome than necessary or agreeable (Fig. 

 13.) 



It is possible that these organs may have some connec- 

 tion with the trachete, although that connection cannot be 

 close; yet here, as in some other insects, the tibial tracheae 

 are specially notable on account of the sac-like enlarge- 

 ment of the upper and of the lower ends of the main tube, 

 and of the presence of a smaller, recurrent branch, which 

 leaves the upper inflated i^ortion to enter near the lower 

 at a varying distance from the extremity. This structure 

 has been observed in the locust (Locu.ita viridissima), the 

 cricket {Gryllus campedris), and in various Orthoptera by 

 Graber; while Sir John Lubbock describes a similar ar- 

 rangement in the tibiae of the ants, especiallj' in Laaiua 

 fiavus. This tracheal structure is well developed in all the 

 tibiffi of Termes Jiavipes, varying in the length of the recur- 

 rent branch and in the more direct or more undulating 

 course of the main trunk of the trachea. In Fig. 12 is 

 shown the appearance in one of the tibiae of the white 

 ants. 



In the locust (Ephippigera vitium Serv.), according to 

 Graber, and in certain other Orthoptera, the main tracheal 

 trunk bears a collection of ganglion-cells and globules 

 supposed to be auditory in function, at least in part, and 

 which, if present in Termes Jiavipes, have escaped mv no- 

 tice. Yet in each tibia of this insect, situated near the 

 outer wall of each, between it, the nerve and the trachea, 

 is the more or less ovate organ referred to, the structure 

 of which bears considerable resemblance to that of what 

 has been accepted as a tibial auditory organ in certain of 

 the Orthoptera. Its position near the upper third of the 

 tibia of Termesflaviges is shown in Fig. 13. 



It is connected with the nerve, and is itself formed of a 

 collection of ganglionic cells and globules, with plainly 

 developed, staff-like bodies, the apical extremities of which 

 are conical, and through the middle of their apparently 

 hollow length passes what seems to be a fibre, presumably 

 a nerve. The external extremity is continuous with a 

 nerve-fibre, five of which, with as many elongated, staff- 

 like bodies, being easily made out, the nerves passing 

 singly and separately up toward the femero-tibial joint, 

 near which they are lost to view, especially after my im- 

 perfect methods of preparation. 



Similar organs have been discovered by Graber in the 

 tibiae of the Locustidise, and by Lubbock in those of cer- 

 tain ants. In reference to the latter, Lubbock says: "At 

 the place where the upper tracheal sac contracts there is, 

 moreover, a conical striated organ, which is situated at the 

 back of the leg, just at the apical end of the upper tracheal 

 sac. The broad base lies against the external wall of the 

 leg, and the fibres converge inwards. In some cases I 

 thought I could perceive indications of bright rods, but I 

 was never able to make them out very clearly. This also 

 reminds us of a curious structure which is in the tibise of 

 the Locustidise, between the trachea, the nerve, and the 

 outer wall. * * * On the whole, then, I am disposed 

 to think that ants perceive sounds which we cannot hear." 



In Termes Jiavipes its position is somewhat different, al- 

 though its situation and its structure are essentially sim- 

 ilar to those referred to by Lubbock and by Graber. It 

 is an organ of fibres, of ganglionic cells and globules, the 

 latter being large and nucleated, and of the long, staff- 

 like bodies already referred to. A partly diagrammatic 

 sketch of the organ is shown in Fi„'. 16, its outer, narrow 

 extremity being attached to the wide nerve just within 

 the external wall of the tibia and the broad base directed 

 toward the external wall of the trachea. 



The rod-like bodies bear a rather remote regemblance 

 to some observed by Graber, in what he considers to be 



