8 CLASSIFICATION OF THE ALEYRODIIXE. % 
It would appear from this that Peal considered the vasiform 
orifice as a special secreting structure and honeydew to be connected 
in some way with the circulation. Miss Bemis seems to have a some- 
what similar idea about the lingula, for she says, 8 " In some species 
there are seen minute, blunt tubes on the apex of the lingula through 
which the fluid may be secreted." 
In the introduction to a paper on Aleyrodida? 13 Tullgren dis- 
cusses the vasiform orifice. His idea of its nature seems to be the 
correct one, but he does not go into detail, and we believe him wrong 
in calling the vasiform orifice the anal opening, for the anus proper 
seems to open within it. 
In the forms examined by us the anus appears to open below the 
linguia (PI. II, fig. 5) which functions as the supraanal plate. We 
are unable to find a definite opening at the tip of the lingula. In 
any case, whether the anus is always at the base or sometimes at the 
apex, as in the Psyllida?, this in no way alters the standing of the 
lingula, which would in either case be the supraanal plate. The 
operculum is a little more difficult to place. It would not appear 
strange if it were believed to correspond to the rudimentary last 
abdominal segment in the Aphididse, as suggested by Tullgren, for 
its position in regard to the anal plate is very similar. It does not, 
however, often appear as a distinct segment, but looks like the 
rolled-back edge of the lingula. 
The substance known as honeydew is, as implied abovel merely the 
excrement of the insects. It is deposited in large quantities by the 
larva-, pupa?, and adults and forms a medium for the growth of 
several fungi. The early pupa? excrete much more than the late 
pupa?, while the larva?, in the earlier instars, excrete the most of all, 
the substance being ejected once or twice for every minute, although 
not always at regular intervals. The salivary glands are two rounded 
bodies situated one on either side of the head and united by small 
ducts. 
The exact nature of the wound of the puncturing seta? of Aley- 
rodidse we have not ascertained, but in all probability it is similar to 
that made by the Aphidida? and the Coccida\ where the seta? pass 
around the outer cells and finally puncture the soft bast cells from 
which the proteid content is taken. These proteid substances form 
the bulk of the insects' food, while much of the sugars taken in at the 
same time are passed out as honeydew. 
THE WINGS. 
The wings are first noticed in the late embryo as imaginal disks 
produced as ingrowths of the hypodermis. These, losing their con- 
nection with the outer layer, soon take on the appearance of closed 
