APPENDIX. 223 



Acarus, sp. ARACHNIDA. 



Found by Cornelius upon the sexual organs of a male 

 Cockroach. 



fi e f. Cornelius, Beitr. zur iiahern Kenntniss von Periplaneta 

 orientalis, p. 35, fig. 23 (1853). 



Evania apjjendigaster, L. IXSECTA (Hymenoptera). 



A genus of Ichneumons, parasitic upon Periplaneta and Blatta. 

 T^/. -Westwood, Trans. Ent. Soc., Vol. III., p. 237 ; Ib., Ser. 

 II., Vol. L, p. 213. 



JSymbius JBlattarum, Sund. INSECTA (Coleoptera). 



The apterous female is parasitic upon P. ainericana and B. 

 yermanica. 



Ref. Sundevall, Isis, 1831. 



SENSE OF SMELL IN INSECTS. 



SINCE the printing of the sheets which describe the organs of 

 special sense, we have become acquainted with two experimental 

 researches of recent date, instituted for the purpose of determining 

 whether other organs, besides the antennae, may be specially con- 

 cerned with the perception of odours by Insects. 



Prof. Graber (Biol. Centralblatt, Bd. V., 1885) has described 

 extensive and elaborate experiments upon various Insects, tending 

 to the conclusion that the palps and the cerci may be sensitive to 

 odours, and that in special cases the palps may be even more 

 sensitive in this respect than the antennas. Cockroaches, decapi- 

 tated, but kept alive for some days, were found to perceive odours 

 by means of their cerci. His general conclusion is that Insects 

 have 110 special sense of smell, but that various parts of the surface 

 of the body are furnished with nerve-endings capable of perceiving 

 strong odours. Prof. Graber's results are known to us only through 

 the abstract given by Prof. Plateau in the paper next to be 

 mentioned. 



Prof. Plateau (Compt. rend, de la Soc. Entom. de Belgique, 1886) 

 relates experiments upon the powers of scent resident in different 

 organs of the Cockroach. Two Cockroaches had their palps (max- 

 illary and labial) removed ; two others had the antennae removed. 

 An evaporating dish, 8 inches in diameter, was then partly filled with 



