HEMIPTERA. 155 



Owing to their small size and similarity in color, it is difficult to 

 distinguish the different species of Aleyrodes in the adult state. 

 But the immature scale-like forms present considerable differences. 

 The most common form that I have met is very flat, nearly circular 

 in outline, and furnished with a beautiful white fringe ( Fig. 131); 

 this fri: 1 of parallel fibres, which radiate from the 



margin of the body ; and its white color contrasts strongly with the 

 dark color of the insect. The segmentation of the body is often 

 represented by prominent wrinkles, which give the insect a minia- 

 ture resemblance to the fossils known to geologists as Trilobite^. 

 Sometimes the fringe of excretion is 

 wanting; and in a common species on 

 maple, the excretion from the margin of 

 the body, instead of extending laterally 

 and forming a fringe, is directed towards 

 the leaf upon which the insect rests, 

 and thus the body is lifted away from FIG. i 3 a.-^*yr/ on maple, 

 the leaf, and perched upon an exquisite palisade of white wax 



The American species of this family have not been studied. In 

 an\' of them become destructive to vegetation, they can proba- 

 bly be destroyed by strong alkaline solutions, as are Coccids. 



Family IV. Ai'iimm/E.* 



Tlu plant-i well-known insects; they infest nearly all 



kinds (.1 tion in all parts of the country. Our most common 



fl-bmlii < . witli long U-gs and 



ant- lich appear <>n various plants in the house and in tin- 



field. Among our common are both winged and wiiu, 



form .it number of species, nearly all of which 



1 1). | ! our larj measure only 6 



or 7 mm. (0.24 or 0.2; inch > in length. 



pear shaped The wii 



forms li -isparent \\ings. 'I i fur- 



nishcil with a few simple \e.in->; but the venation is more i 



Aphldidtt, Aphis: perhaps from afhysso (d0vcr<rv), to drink up liquids. 



