308 INSECTS. 



veined ; two smaller leaves coquettishly decorate a pro- 

 minence on the base of each antenna, slender leaflets 

 fringe the first and second pairs of legs, and the abdo- 

 men is bordered by a series of broad leaves like those 

 forming the tiara. 



The history of Aphides is very remarkable. In the 

 spring, numbers of fertile females, and females only, are 

 hatched from eggs laid the autumn before. These, 

 rapidly attaining to their full growth, but never to the 

 possession of wings, give birth not to eggs, but to young 

 fertile females like themselves. These repeat the same 

 process, which occurs again and again, until at last nine 

 generations have been produced, when, autumn having 

 arrived, males as well as females are produced, which 

 sometimes, but not always, develope wings ; the usual 

 pairing takes place, the female lays her eggs and dies, 

 and from these eggs the next year's series of generations 

 is produced. 



The true pupa may be known from the permanently 

 wingless female by its possessing the rudiments of wings. 

 The underground species of Aphis never develope wings. 



The third family of Dimera contains only the genus 

 Aleyrodes ; pretty little insects already spoken of as so 

 covered by a fine white dust as to have the appearance 

 of tiny Moths (PI. XII., fig. 6, 6 a). The wings are 

 carried nearly horizontally when at rest. The abdomen 

 has none of the tubercles or other appendages common 

 in this order. The head is remarkable as having four 

 eyes, or, to use more scientific language, as having the 

 eyes "parted in the middle," as are those of Gyrinus 

 (see p. 70, fig. 32), and some few other insects. There 

 are only two British species of Aleyrodes. They are 

 about | inch in length. 



