2i6 THE COURTSHIP OF ANIMALS 



developments in the Beetles seems to be shown by 

 the case of certain carnivorous Beetles, of which one 

 species (Taphroderes distortus) may serve as an example. 

 Herein the left jaw takes the form of a long, crooked 

 strap-shaped outgrowth, whose purpose cannot even be 

 conjectured. And in this connection one may cite the 

 case of certain species of Homoptera — Bugs — which occur 

 in tropical South America. Here, in both sexes, as may 

 be seen in Plate 40, Fig. 4, the neck-shield is produced 

 backwards far beyond the body, to form a most 

 elaborate superstructure which appears to confound the 

 most ingenious attempts at interpretation. 



It is to be noted that wherever special structures are 

 necessary for the performance of specific acts such as 

 are of vital importance to the well-being of the race, 

 they are developed to perfection : there is little or no 

 variation in their size, and no doubt as to their purpose. 

 Thus in many species means are necessary to enable the 

 male to seize and hold the female during the sexual 

 embrace. In the Water Beetle of our ponds and ditches 

 (Dytiscus marginalis) the male bears a very remarkable 

 sucker on each fore-leg, the adhesive surface of which, 

 under the microscope, reveals an extraordinary complexity 

 and wondrous beauty. This sucker forms a very con- 

 spicuous " secondary sexual character,'* and is used in 

 embracing his mate, whose back is deeply grooved to 

 enhance the hold of the suckers. In some species 

 punctures take the place of grooves. Suckers, like those 

 of Dytiscus are met with again in a Wasp {Crabro 

 cribrarius). In another genus of Beetles {Penthe) cited 

 by Darwin, the antennae of the male have a few of the 

 middle joints dilated and their under surfaces furnished 

 with a cushion of hairs to aid in the sexual embrace. 



