8 
Coccidae (Hemiptera, or true bugs). Notwithstanding the many 
superficial differences which distinguish them, their structure is 
essentially similar. One of the most striking features of this 
structural similarity, shared also by the leaf-hoppers and the 
aphids, two other families of plant lice common in Hawaii, is the 
character of the mouthparts ; and as this determines the manner 
in which the insect gains its sustenance from the plant and also 
has an important bearing on the means of controlling insects of 
this type, it is perhaps worth while at this point to give some 
consideration to the structure of the mouth. The type of mouth- 
parts possessed by the greater number of injurious insects 
(beetles and caterpillars, for example) is what is known as ''cut- 
ting and biting mouth parts," the main feature of which is the 
apposed heavy-knife-edged jaws which tear and rend the plant 
tissue to fragments so that they can be gathered together by the 
remaining parts, ground and swallowed. The plant where the 
insect is feeding is entirely consumed. Not so, however, with 
the plant louse. Its mouth parts, while homologous throughout, 
are different both in structure and purpose. Instead of the heavy 
lamellate jaws, there are apposed long slender stylets or filametous 
rods with grooved or channelled inner surfaces forming a pierc- 
ing and sucking organ, with the pharyngeal pump behind them, 
and instead of organized tissue, unorganized tissp" ^s consumed. 
That is to say, the fluid contents of the cells, referred to loosely 
as the juice of the plant, is sucked out of it, and the solid mat- 
ter suspended in it is strained out in the alimentary tract of the 
louse and constitutes its food. Inasmuch as they take only a 
solution of food, obviously large quantities of the juice of the 
plant must be absorbed to meet the requirements of their growing 
bodies, but unless the infestation of these insects is very severe 
and they are present in extremely large numbers, their feeding 
does not prove much of a drain on a succulent plant like the 
pineapple — on tender leaves, yes ; but on a hardy, succulent plant 
they make little impression except when they are numerous. The 
chief injury resides in the puncture of the epidermis of the plant, 
for this furnishes an entrance for the spores of pathogenic organ- 
isms, which often invade the tissues and quickly destroy them. 
Unfortunately the pineapple is very susceptible to some rapidly- 
developing rots, which thus gain access to the plant, so it should 
be apparent that it is very essential that these insects be dis- 
couraged from multiplying on the plant just as much as possible. 
Another feature of the life of these insects which should not 
be overlooked is their close association with ants. This and sev- 
eral other related families of insects are peculiar in the respect 
that their representatives uniformly excrete a sugary fluid known 
as honey-dew, which many ants find good provender. The ants 
have become so habituated to this food that they tend the insects 
in much the same way as man does his domestic animals, and it 
is often the case that in waging war on the scale insects, et cetera. 
