BUTTERFLIES AND MOTHS. 323 



gists for the good of man. We cannot, however, at present thus 

 explain the elegant diversity in the colors of many caterpillars; 

 but any species which had at some former period acquired a dull, 

 mottled, or striped appearance, either in imitation of surround- 

 ing objects, or from the direct action of climate, &c., almost cer- 

 tainly would not become uniform in color, when its tints were 

 rendered intense and bright; for in order to make a caterpillar 

 merely conspicuous, there would be no selection in any definite 

 direction. 



Summary and Concluding Remarks on Insects. — Looking back 

 to the several Orders, we see that the sexes often differ in 

 various characters, the meaning of which is not in the least 

 understood. The sexes, also, often differ in their organs of sense 

 and means of locomotion, so that the males may quickly dis- 

 cover and reach the females. They differ still oftener in the 

 males possessing diversified contrivances for retaining the fe- 

 males when found. We are, however, here concerned only in a 

 secondary degree with sexual differences of these kinds. 



In almost all the Orders, the males of some species, even of 

 weak and delicate kinds, are known to be highly pugnacious; 

 and some few are furnished with special weapons for fighting 

 with their rivals. But the law of battle does not prevail nearly 

 so widely with insects as with the higher animals. Hence it 

 probably arises, that it is in only a few cases that the males have 

 been rendered larger and stronger than the females. On the 

 contrary, they are usually smaller, so that they may be developed 

 within a shorter time, to be ready in large numbers for the 

 emergence of the females. 



In two families of the Homoptera and in three of the Orthop- 

 tera, the males alone possess sound-producing organs in an 

 efiicient state. These are used incessantly during the breeding- 

 season, not only for calling the females, but apparently for 

 charming or exciting them in rivalry with other males. No 

 one who admits the agency of selection of any kind, will, after 

 reading the above discussion, dispute that these musical instru- 

 ments have been acquired through sexual selection. In four 

 other Orders the members of one sex, or more commonly of both 

 sexes, are provided with organs for producing various sounds, 

 which apparently serve merely as call-notes. When both sexes 

 are thus provided, the individuals which were able to make the 

 loudest or most continuous noise would gain partners before 

 those which were less noisy, so that their organs have probably 

 been gained through sexual selection. It is instructive to reflect 

 on the wonderful diversity of the means for producing sound, 

 possessed by the males alone, or by both sexes, in no less than 

 six Orders. We thus learn how effectual sexual selection has 



