STRUCTURE OF THE ORGANS OF SMELL 271 



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twenty pairs were placed in a moderately sized box. On the next 

 morning twelve pairs of them were found coupling. Hauser then, 

 after removing the first lot, placed a new set of thirty pairs in the 

 same box, cut off all the antennae of the males and those of a number 

 of females. On the following morning only four pairs were found 

 coupling, and at the end of three days five others were observed 

 sexually united. 



From these experiments Hauser inferred that those insects deprived of their 

 antennae were placed in the most favorable situation, such as they would not 

 find in freedom; for the space in which the insects moved about was so limited 

 that the males and females must of necessity meet. But at the same time the 

 results of the experiments cannot absolutely be regarded as proving that the 

 males, after the loss of their antennae, were then not in condition to find 

 the females, because in the case of the above-mentioned moths, under similar 

 conditions, after the extirpation of the antennae no sexual union took place. If, 

 however, the experiments made do not all lead to the results desired, Hauser 

 thinks that the results agree with those of his histological researches, that in the 

 greater number of insects the sense of smell has its seat in the antennae. His 

 results also agree with those of Ferris. 



Structure of the organs of smell in insects. The olfactory organs 

 consist, in insects, i.e., all Orthoptera, Termitidae, Psocidae, Dip- 

 tera, and Hymenoptera, also in most Lepidoptera, Neuroptera, and 

 Coleoptera, 



1. Of a thick nerve arising from the brain, which passes into the 

 antennae. 



2. Of a sensitive apparatus at the end, which consists of staff-like 

 cells, which are modified hypodermis cells, with which the fibres of 

 the nerves connect. 



3. Of a supporting and accessory apparatus, consisting of pits, or 

 peg- or tooth-like projections filled with a serous fluid, and which 

 may be regarded as invaginations and outgrowths of the epidermis. 



Hauser adds a remark on the distribution of the pits and teeth in 

 the larvae of insects, saying that his observations are incomplete, 

 but that it appears that in the larvae the teeth are most generally 

 distribiited, and that they occur not on the antennae alone, but on 

 the palpi ; but in very many larvae neither pits nor teeth * occurred. 

 In the Myriopoda teeth-like projections occur on the ends of the 

 antennae. In Lithobius they form very small, almost cylindrical, 

 pale organs. 



In the course of a special description of these sense-organs in the 

 Orthoptera, Hauser describes at length those of (Edipoda coerulescens 



1 Hauser here uses the word taster, but this means palpus or feeler. It is probably 

 a lapsus pc nti se for teeth (Kegeln). 



