14:4 PLANT LICE, 
beak is two-jointed, and varies greatly in length; sometimes it 
is longer than the body. The compound eyes are prominent; and 
ocelli are also usually present. The antennz are from three- to 
seven-jointed. On the dorsal aspect of the sixth abdominal seg- 
ment there is, in many species, a pair of tubes, through which a 
sweet, transparent fluid is excreted. In some genera these 
organs are merely perforated tubercles; while in still other genera 
they are wanting. The fluid which is excreted through the 
Fic. 133—Ants milking plant-lice. After Figuier. 
abdominal tubercles is the substance known as honey-dew. It is 
sometimes produced in such quantities that it forms a glistening 
coating on the leaves of the branches below the plant-lice, and 
stone-walks beneath shade-trees are often densely spotted with it. 
This honey-dew is fed upon by bees, wasps, and ants (Fig. 133). 
The bees and wasps take the food where they find it, paying 
little, if any, attention to its’source. But the ants recognize in 
the plant-lice useful auxiliaries, and often. care for them as man 
cares for his herds. 7 
a Ee ee 
“we 
