antennj:. 59 



I have been unable to find one wliicli was perfect 

 in this respect. 



In TemiAetonia the apical segment is the longest 

 and is ringed, while the third, on the contrary, is 

 simple. The genera Achorutes and Podura, as well as 

 the species belonging to the two small families 

 LiPUEiD^ and ANOUEiDiE, all have the antennae quite 

 short, simple, and 4-jointed. 



In his original description of Isotoma stagnoriim 

 (Podura aquatica cinerea) De Geer^ remarked with 

 surprise that the antennae were not always symmetrical, 

 but that, while four was the normal number of seg- 

 ments, many specimens had one antenna with four, as 

 usual, the other with only three. The individual 

 which he figured was in this condition. Latreille, also, 

 in his ' Organisation exterieure et comparee des 

 Insectes de I'Ordre des Thysanoures,'" observes that 

 the antennae of the PoduridcB " sont sujets a des 

 monstruosites, puisque je possede un individu ou I'une 

 des antennes a trois articles, et I'autre deux. Je les 

 ai examinees, I'animal etant vivant, et je n'ai aper9u 

 aucune trace de mutilation. Les variations ainsi que 

 les anomalies relatives au nombre des yeux lisses 

 semblent indiquer que la nature tatonne ici, en quelque 

 sorte, et qu'il ne faut pas des-lors attacher une grande 

 importance a ces caracteres numeriques." 



M. I'Abbe Bourlet gave as a character of his genus 

 Heterotoma (a name which he subsequently changed 

 for ^theocerus), which is composed principally, but 

 not entirely, of the species forming Templeton's 

 genus Orchesella, that the segments of the antennae 

 varied from 2 to 5, those even of the same individual 

 being often dissimilar in the number of their segments. 

 He was aware that M. Macquart regarded these difier- 

 ences as either abnormal or accidental ; but he 

 rejected this explanation because — " 1°. Dans le cas 

 ou les antennes sont inegales, le dernier article de la 



1 ' Act. Soc. Reg. Sci. Upsal.,' 1740, p. 64. 



2 ' Nouv. Ann. du Museum,' v. i, p. 186. 



