272 K. T. LEWIS ON A 



year he was able to secure some farther specimens, one of which 

 he could personally vouch for as having produced certain squeak- 

 ing sounds during and after its capture. I found on examina- 

 tion that the species was the same as that formerly sent, but 

 although the insects were extremely dry, and so hard that an 

 entomological pin bent under the pressure applied without being 

 able to penetrate the thorax, the abdomen was this time fully 

 extended, and the first glance revealed the existence of an ex- 

 tremely perfect and competent stridulating organ (Fig. 4) 

 which had escaped notice before through having been com- 

 pletely retracted within the preceding segment. 



The general colour of the abdomen of this ant under ordinary 

 light is black; it is also highly polished and covered sparely with 

 soft brown hairs with the exception of the 2nd ventral segment 

 counting from the stalk. This is seen at once to differ entirely 

 in appearance and surface structure from all the others, being 

 free from hairs and apparently striated or ribbed from end to 

 end. Under a very moderate power it is seen that these stria- 

 tums are not continuous lines, but that they are broken up into 

 numerous distinctly separate sections of slightly unequal length, 

 so that whilst the longitudinal parallelism of the strias is main- 

 tained, the rows of which they are composed present a somewhat 

 zigzag arrangement transversely. The average number of 

 striae across the band is 26, which gives them a closeness of 

 about 1,650 to the inch. Under a |in. power, however, the 

 structure of the band becomes more apparent, and it is then 

 perceived that the surface is not really furrowed, but that it is 

 set with rows of minute elevations not unlike the cogs or teeth 

 of a ratchet, their anterior face being slightly concave and 

 rising at an angle of about 30°, whilst the posterior face is 

 almost perpendicular to the general surface of the band. The 

 ridge of each tooth is narrow, but nearly level for more than f 

 of its length, the ends being rounded off and every angle 

 smoothed and polished iuahigh degree, the formation of the teeth 

 presenting a similarity to some analogous structures met with 

 amongst the Orthoptera. The shape and arrangement of these 

 teeth causes them to assume a remarkably different appearance 

 according to the direction in which the light is allowed to fall 

 upon them. If obliquely illuminated from the posterior side 

 they appear as rows of extremely fine lines (Fig. 7), the light 



