HORN EXPEDITION—ZOOLOGY. APPENDIX. 
415 
actually hearing the whistling sound produced when the animal was irritated, and 
could be watched—as it subsequently often was by several of us—rubbing the 
palps alternately up and down on the mandibles, both pai’ts moving at the same 
time. Whilst the palp of one side was elevated, that of the other was depressed. 
The sound resembled a whistling noise, and could be heard at night in a room 
when all was quiet at a distance of eight or ten feet. 
Unfortunately, no male specimen was secured ; but seeing that it is so well 
developed in the female, and judging by the size and powerful claws of the animal, 
the probabilities are strongly in favour of the idea that the organ is used as a 
signal to warn oft’ would-be aggressors. 
DESCRIPTION OP PLATES. 
All the figures refer to Phlo^ius (PJmctus) c?-assipes, and, except in the case of 
Fig. 2, the outlines have been drawn under the camera lucida. 
Fig. I.—Inner surface of the basal joint of the palp. x 8. 
,, 2.—Mandible seen from the outer side. x 2. 
,, 3.—Four of the longest keys in situ. Zeiss A, oc. 2. 
,, 4.—Section across the length of the inner face of the palp to show the series 
of keys in position. Zeiss A,* oc. 4. 
,, 5.—Upper part of the outer face of the mandible showing the spines, x 8. 
„ 6.—Section across the upper part of the mandilfte to show the series of spines 
in position. Zeiss A,* oc. 4. 
