THE HONEY DEW. 
45 
fluid from moderate-sized pouches, as lar^e as hazel- 
nuts ; nevertheless, this watery substance does not 
appear to incommode the inhabitants, for it is 
lodged in a quantity of meal-like powder or floccu- 
lent matter, which effectually protects them from 
drowning. 
The history of Pemphigus bursarius which con- 
structs these curious gall-like excrescences will be 
treated of under the diagnosis of that species, but 
here it may be said, that doubts must be expressed as 
to the liquid above noticed being a secretion from the 
Aphides ;“-“it is too large in quantity. It is more 
probable that it consists of transuded sap, occasioned 
by the punctures and incessant irritation set up in 
the walls of the purses by the rostra of the Aphides. 
In this opinion I am glad to be supported by Mr. 
M^Lachlan, who described iii 1866 some large galls he 
found on the elms near Deal. They were made by 
ScMzoneura ulmi, and filled with a similar liquid, 
which he considered to be sap, mixed with a white 
powder.* 
On the other hand, Kaltenbach describes this liquid 
as a whitish, thick honey dew, of which one could 
fill a middle-sized thimble,” 
Although it may be thought somewhat fanciful to 
ascribe urinary functions to the cornicles, as some 
authors have done, yet there can be no doubt of their 
offices as excreting orifices of some kind. When we 
consider that the life of an Aphis is almost wholly 
spent in pumping into its body vegetable sap, we may 
ask into what form does the effete matter pass ? 
We have seen that Aphides are provided with a dis- 
tinct stomach and alimentary canal, ending in a 
csecum, and that certain fluid products are from time 
to time forcibly expelled from its exit. It is clear that 
the cornicles do not functionize in this manner. I have 
been unable to trace with certainty any gland at the 
base of these tubes, although in several instances I 
* Vide ‘ Entom. Moiitli. Mag.,’ voL iii, p. 157. 
