284 INTRODUCTION TO ZOOLOGY chap. 



Sub-order 2 : Homoptera (Scale Insects, Green-fly, 

 Bark-lice, Cuckoo-Spit Insects, etc.). 



In all this division of the Ehyncota, the consistency of the 

 front wings is the same throughout, and, in many, all four 

 wings are membranous and transparent. They cover the 

 body in a roof-like manner, the two pairs sloping upwards 

 towards each other, so that their inner margins touch along a 

 median longitudinal line. 



Family 1 : Aphidae (Green-fly or Blight Insects) 



These insects are only too well known superficially, and 

 the name " Green-fly " brings up a mental picture of clusters 



of the minute, wingless, soft, 

 green creatures, on our rose- 

 buds or daisy heads, covering 

 the under surface of sycamore 

 leaves, or infesting many an- 

 other plant, feeding on the 

 juices of young shoots and 

 leaves, and doing an enormous 

 amount of damage. 



FIG. 211. --An Aphis off Sycamore. r^^ different 



(Wingless form.) , • t r r^ a 



kinds of Green-fly, varymg in 

 colour, size, and habits, but all having smooth, plump, segmented 

 bodies, a head provided with two long dark antennae, a 

 pair of compound eyes, and mouth-parts as in the Heteroptera, 

 but here the sucking-tube, when not in use, is pressed against 

 the under side of the thorax. The thorax has three pairs of 

 long thin legs, but in the majority of cases is wingless until 

 the autumn, when many winged forms appear. The abdomen 

 in many species bears on the fifth abdominal segment a pair 

 of short tubes which project upwards and secrete an oily 

 juice, often to be seen as a shining drop at the end of each 

 tube. This substance used to be looked upon as the " honey- 

 dew " which is eaten by ants ; it is, however, waxy in nature 

 and not sweet, the attractive " honey-dew " being a secretion 

 which is given out copiously from the end of the alimentary 

 canal, often making sticky the whole leaf inhabited by the 

 Aphides, or even falling in little drops to the ground below. 



