SG2 ON THE STRUCTURE OF THE ANTENN/E, ScC. 



is to be found between them. If, however, the antennae 

 are to be regarded as affording the characters of genera in 

 this order, it must be evident, even from Mr. Curtis's plate of 

 Ceratop/ii/ll/fs alone, that there ought to be a much greater 

 number of genera established according to the variations in the 

 structure of those organs. 



I should however be inclined to consider, from analogy, that 

 the antenna of P. cams have the same number of joints as 

 the P. hirundinis; and indeed I have but little doubt that all 

 the other species are formed upon the same type, the supposed 

 numerous articulations, represented by Mr. Curtis in some of 

 the species appearing to me to be merely deeper impressions 

 of the marginal denticulations of the terminal joint : indeed, 

 according to M. Duges, the antennas, both of the Pidices and 

 Ceratophijlli, are three-jointed, the only material difference 

 consisting in the variation in the length of the first and second 

 joints. 



Hence it can scarcely be considered that the genus Cera- 

 tophyllus is well founded. The species, however, figured by Mr. 

 Curtis, Cer. elongatus, as well as the Cer. vespertilionis, and 

 probably Cer. bifasciatus, and Pulex mnsculi, Dug. ; together 

 with a Chinese species, which has been kindly presented to 

 me by the Rev. Leonard Jenyns, exhibit a general form so 

 different to that of the other fleas, that I cannot help thinking 

 them, on that account, entitled to form a distinct group ; for 

 which (as the name CeratophyUus must likewise be rejected in 

 consequence of having been previously employed in botany) 

 the generic name of Ischnopsyllus may not be deemed inap- 

 plicable, the characters of which I propose to detail in a 

 memoir, upon which I am at present occupied, upon Bat 

 Parasites. 



In conclusion, I may be allowed to observe, without how- 

 ever venturing to offer any decided opinion upon so difficult a 

 question, that no group of insects appears to afford so striking 

 an instance in support of the opinion, that the antennae are 

 organs of hearing, as those of the order under consideration. 

 Such, it will be seen from the passage quoted above, was the 

 doubtful opinion of Mr. Curtis; and when we notice the 

 peculiar form of the aperture in which these organs are placed, 

 and its situation at the back of the head on each side behind 

 the eyes, such an opinion seems to have some reasonable 



