196 



The Orders of Insects 



by unfertilised females ; in autumn, eggs are laid by fertilised 

 females ; these are iiatched in the ensuing spring (122). 



Aleyrodidae. — The AUyrod'ida: are a small family of tiny delicate 

 insects in which both sexes have evenly rounded, white wings, 

 each with only one median nervure. The feelers have six seg- 

 ments, whereof the second is lengthened. 



Coccidae. — The Cocdda or Scale-insects are distinguished by the 

 very striking difference between the sexes. The males have long 



F. Dctmers, del. 



Fig. 100. — Plant-louse {AJ>his brassicce, Linn.) Europe, a. male, magnified 

 15 times ; b. head and feeler, magnified 30 times ; c. wingless female, 

 magnified 12 times ; d. head and feeler, magnified 30 times. From 

 Weed, Insect Life, vol. 3 (U.S. Dept. Agr.). 



feelers and cercopods, well-developed forewings and greatly reduced 

 hindwings, and vestigial jaws (fig. 1 10 a), while the sluggish females 

 (fig. no e) never acquire wings, and ultimately settle down to a 

 stationary life beneath the waxy secretion which hardens into a 

 protective "scale" (see fig. 170); sheltered by this they suck 



