196 APTERA 



of the integument. So far as tolerance of heat and. cold goes, 

 the Aptera can apparently exist in any climate, for though some 

 of the species extend to the Arctic regions, others are peculiar to 

 the tropics. 



Thysanura are recorded by Klel:)s and Scudder as occurring 

 commonly in amber ; the latter author has described a fossil, 

 supposed to be a Lepisma, found in the Tertiary deposits at 

 Florissant. Scudder has also described another fossil, likewise 

 from Florissant, which he considers to form a special sub-order of 

 Thysanura Ballostoina^hut it is extremely doubtful whether 

 this anomalous creature should be assigned to the Order at all. A 

 still older fossil, Dasylejptus lucasii Brongniart, from the Carbon- 

 iferous strata in France, is considered to belong to the Order 

 Aptera, but it must be admitted there is some doubt on this 

 point. 



The interest aroused in the minds of naturalists by the 

 comparatively simple forms of these purely wingless and therefore 

 anomalous Insects has been accompanied by much discussion as to 

 their relations to other Insects, and as to whether they are 

 really primitive forms, or whether they may perhaps be degenerate 

 descendants from some less unusual states of Insect-life. Mayer 

 and Brauer dissociated our Aptera entirely from other Insects, 

 and proposed to consider the Hexapoda as being composed of two 

 groups (1) the Apterygogen^a, consisting of the few species we 

 have been specially considering ; and (2) the Pterygogenea, includ- 

 ing all the rest of the immense crowd of Insect forms. They 

 were not, however, able to accompany their proposed division by 

 any satisfactory characters of distinction, and the subsequent 

 progress of knowledge has not supported their view, all the best 

 investigators having found it necessary to recognise the extremely 

 intimate relations of these Insects with the Orthoptera. Meinert 

 thought that Zepisina must be included in the Orthoptera ; Grassi 

 proposes to consider the Thysanura as a distinct division of 

 Orthoptera ; and Oudemans recognises the close relations existing 

 between Machilis and Orthoptera proper. Finot includes the 

 Aptera in his Orthopteres de la France, and a species of Jajyyx 

 has actually been described by a competent entomologist as an 

 apterous earwig. At present, therefore, w^e must conclude that 

 no good distinction has been found to justify the separation of 

 the Aptera from all other Insects. 



I 



