426 THE DESCENT OF MAIT 



bottles by druggists for the good of man. We cannot, how- 

 ever, at present thus explain the elegant diversity in the col- 

 ors of many caterpillars; but any species which had at some 

 former period acquired a dull, mottled, or striped appear- 

 ance, either in imitation of surrounding objects, or from the 

 direct action of climate, etc., almost certainly would not be- 

 come uniform in color, when its tints were rendered intense 

 and bright; for in order to make a caterpillar merely con- 

 spicuous, there would be no selection in any definite direction. 



Summary and Concluding Remarhs on Insects. — Looking 

 back to the several Orders, we see that the sexes often difEer 

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

 least understood. The sexes, also, often difEer in their or- 

 gans of sense and means of locomotion, so that the males 

 may quickly discover and reach the females. They differ 

 still oftener in the males possessing diversified contrivances 

 for retaining the females when found. We are, however, 

 here concerned only in a secondary degree with sexual 

 differences of these kinds. 



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

 of weak and delicate kinds, are known to be highly pugna- 

 cious ; 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 fthat 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 

 Orthoptera, the males alone possess sound-producing organs 

 i 1 an efficient state. These are used incessantly during the 

 breeding-season, not only for calling the females, but appar- 

 ently 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 



