348 SEXUAL SELECTION. Part II. 



with these species, and the males require great strength 

 and size in order to carry the females through the air. 

 Increased size has here been acquired in opposition to 

 the usual relation between size and the period of de- 

 velopment, for the males, though larger, emerge before 

 the smaller females. 



We will now review the several Orders, selecting such 

 facts as more particularly concern us. The Lepidoptera 

 (Butterflies and Moths) will be retained for a separate 

 chapter. 



Order, Thysanura.—The members of this Order are 

 lowly organised for their class. They are wingless, 

 dull-coloured, minute insects, with ugly, almost mis- 

 shapen heads and bodies. The sexes do not differ ; but 

 they offer one interesting fact, by shewing that the males 

 pay sedulous court to their females even low down in the 

 animal scale. Sir J. Lubbock 17 in describing the Smyn- 

 thurm liiteus, says : " it is very amusing to see these 

 " little creatures coquetting together. The male, which 

 " is much smaller than the female, runs round her, and 

 " they butt one another, standing face to face, and 

 " moving backward and forward like two playful lambs. 

 " Then the female pretends to run away and the male 

 " runs after her with a queer appearance of anger, gets 

 " in front and stands facing her again ; then she turns 

 " coyly round, but he, quicker and more active, scuttles 

 "round too, and seems to whip her with his antennae; 

 " then for a bit they stand face to face, play with their 

 " antennae, and seem to be all in all to one another." 



Order, Diptera (Flies). — The sexes differ little in 

 colour. The greatest difference, known to Mr. F. Walker, 



" ' Transact. Linnean Soc.' vol. xxvi. 1868, p. 296. 



