868 THE DESCENT OF MAN 



and among the Fossores, the males of the Meihoca ichneu- 

 monides are larger than the females. The explanation of 

 this anomaly is that a marriage flight is absolutely necessary 

 with these species, and the male requires great strength and 

 size in order to carry the female through the air. Increased 

 size has here been acquired in opposition to the usual rela- 

 tion between size and the period of development, 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 lowly organized 

 order are wingless, dull-colored, minute insects, with ugly, 

 almost misshapen heads and bodies. Their sexes do not 

 differ; but they are interesting as showing us that the males 

 pay sedulous court to the females even low down in the 

 animal scale. Sir J. Lubbock" says: "It is very amusing 

 to see these little creatures {Smynthurus luteus) 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 color. 

 The greatest difference, known to Mr. F. Walker, is in the 

 genus Bibio, in which the males are blackish or quite black, 

 and the females obscure brownish orange. The genus Ela- 

 phomyia, discovered by Mr. Wallace" in New Guinea, is 



" See "The Transactions of the Linnean Society," volume zzyi., 1868, 

 p. 296. 



'8 "The Malay Archipelago," vol. ii., 1869, p. 313. 



