SCALE-INSECTS. 15 
believe that the Coccidide of this country are likely to furnish 
any products of a useful or commercial character. 
There is, however, one substance produced by these insects 
which has an injurious effect upon the plants they grow on. 
This is a transparent glutinous fluid, apparently analogous to 
that exuding from Aphides, and which may receive the name of 
“honeydew,” as in that family. In fact, this fluid would seem 
to be produced by most of the Rhynchota, for the Psyllide and 
Aleurodid also excrete it. The quantity issuing from Coccids 
seems to vary greatly. In some cases—e.g., Lecanium hesperidum, 
Ctenochiton viridis or perforatus, Fiorinia astelie—the insects 
appear to discharge ‘ honeydew”’ freely ; in others—e.g., My- 
tilaspis pomorum, Rhizococcus fossor—none, or scarcely any fluid, 
is excreted. But in no case does it appear that our Coccids* 
form honeydew to the same extent as the Aphides, which are 
stated to produce sometimes quantities that may be gathered 
from the leaves or the soil by the pound weight. It is not 
so much the amount exuding from each insect as the great 
number of insects on a plant which renders the Coccid honeydew 
obnoxious : each individual may excrete only a little, but when, 
as usually happens, there are many hundreds of individuals 
together, the result, for the reasons given below, becomes 
important to the tree. 
There is every reason to believe that the honeydew of Coc- 
-cididee is of similar character to that of the Aphidide, and, 
according to analyses by Boussingault, of Paris, and Gunning, of 
Amsterdam (Buckton, “‘ Brit. Aphides,” Vol. I., pp. 42, 43), the 
Aphidian heneydew contains a very large quantity of sugar, and, 
curiously enough, cane-sugar. Some observers, noticing in its 
composition also glucose and dextrine, have considered it as 
of vegetable rather than animal origin; but the weight of 
_ evidence appears to make it certainly the product of the Aphides. 
As the present work is intended rather as a manual for gardeners 
and tree-growers than as a purely scientific publication, there is 
no need to enter more fully into the subject here: it may there- 
fore be simply stated that the honeydew of Coccidide probably 
contains a large proportion of sugar in various forms, 
. The mode in which this substance is excreted by the insects 
' differs somewhat from that of the Aphididee. On the abdomen 
* Gossyparia mannipara, an Arabian Coccid, is said to excrete so much that 
the Arabs ‘cat it with their bread like honey.” Buckton, ‘‘ Brit. Aphides,” 
‘Vol. I., p. 42. 
