‘Sliffer’s Patches’ and the Thermal Sense in Acrididae (Orthoptera)

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Abstract
The term ‘Slifer’s patches’ is applied in this paper to the series of specialized areas of cuticle which Slifer named ‘antennal crescents’ and ‘fenestrae’. None of the existing evidence supports her suggestion that these patches have a thermoreceptive function. Behaviour changes caused by damaging them can be reproduced by damaging other parts of the cuticle. The antennal-lowering response is not dependent upon stimulation of the patch situated near the antennal base. Destruction of all of the patches does not reduce the ability of locusts to orientate to, and assume the basking posture under the influence of, a lamp ; nor does it reduce their ability to respond similarly to a heat source in darkness and with a cooled floor on which the locusts move. It does not change the leaning response produced by heat stimulation of decapitated locusts. The antennal scape and articular membrane are more effective in producing an antennal-lowering response when stimulated by a hot probe than are the antennal patches or adjacent areas. The median response-time for kicking of the hind legs in response to the local application of a hot probe to the abdomen is shorter when the probe is applied to a part of the normal cuticle than when it is applied to a patch. The antenna, including the flagellum, is sensitive to heat. Stimulation of the distal part of the flagellum by means of a hot wire produced an avoiding response when the wire temperature rose above 40°C. If one antenna is removed locusts in arena tests show a marked tendency to turn the intact side of the body away from a lamp, or a heat source in darkness. Locusts with both antennae removed show a reduced tendency to akinesis under the influence of a heat source in darkness. The detection by locusts of heat stimulation at intensities above the nociceptive threshold may depend on a sensory system which is at least partly distinct from that involved at lower intensities.