40 
BRITISH APHIDES. 
ordinary passage, but also by two setiform tubes placed 
one on each side just above it.’^‘^ 
De Geer and Kyber remarked that this secretion is 
not expelled from tlie cornicles of Aphides, as is usually 
supposed, but that it is voided from the anus of the 
insect. Any observer may prove the forcible ejection 
of a liquid from this last passage by gently stimulating 
with a bristle the abdomens of the full-fed individuals 
of a colony of LacJinus saligna, a large black Aphis 
which sometimes infests the willow tree in such quan- 
tities that occasionally it kills it.f Many of these 
insects will, by this treatment, erect the terminal rings 
of their bodies, upon the apex of which a clear drop of 
fluid will, for a moment, appear. If this is not quickly 
withdrawn by an attendant ant, usually in quest of the 
sweet morsel, it is projected by a peculiar jerk to a 
considerable distance, and it is caught on the upper 
surfaces of the leaves below. 
The same action may be seen in the black masses of 
the elder Aphis, Aphis sambuci, which also are much 
visited by ants for the same purpose. 
A similar sweet secretion is elaborated by Psylla 
cratcegi^ which also appears to be acceptable to ants, 
since they resort to them largely and intermix with 
their companies. 
It may be stated that the substance of Kirby and 
Spence’s remarks is accepted as true by almost al; 
aphidologists, dating from the veteran De Geer to 
Kaltenbach, Koch, and Passerini. 
There are, however, other observers who ascribe a 
vegetable origin to the honey dew. Their objections 
seem to be principally based on the presumed absence of 
Aphides on the leaves which are loaded with the saccha- 
rine matter. Yet it is well known that Aphides crowd 
almost exclusively the lower surfaces of the leaves 
which grow on trees of great elevation, and thus, after 
* Kirby and Spence’s ‘ Introduction to Entomology,’ voL i, p. 210, 
and vol. ii, p. 18. 
f Vide Mr Smee’s account of tbeir ravages on the willow in ‘ My 
Garden,’ pi. xxiii, figs. 1 — 4, p. 477. 
