Jan., 1908.] 
Notes on the Aphididae. I. 
2 45 
having nothing else to live on were forced to follow the example 
of the parent. However, after a detailed study of the adapta¬ 
tions of the insect to its Semi-aquatic life I am convinced that it is 
a true semi-aquatic insect though not necessarily confined to 
Philotria but may feed on other aquatic plants. The colony was 
probably started by a winged migrant or by wingless forms 
brought in with Philotria or some other water plant. 
The latter conclusion was strengthened by Mr. H. H. Severin, 
who reports that a similar aphid was very troublesome on aquatic 
plants in the green house at Wisconsin State University. Pro¬ 
fessor F. L. Landacre also says he has noted probably the same 
insect on various aquatic plants at Columbus several years ago. 
While doing some field work in Sandusky Bay a few years ago 
I noticed large colonies of aphids frequenting the lotus buds, but 
at present cannot say as to the identity of the two species. 
One peculiarity which attracted my attention was the ease 
with which the aphids walked over the surface of the water, or 
were found half submerged in an attempt to feed on aquatic 
plants. An accurate examination of the forms showed that on 
either side of the thorax were located three pairs of wax glands. 
These glands resemble in all respects the thoracic or abdominal 
wax glands found in many other aphididae, but in every instance 
with which I am familiar the thoracic glands occur near a median 
dorsal line. Another fact which brings out this remarkable con¬ 
dition more forcibly is the relation of a small thoracic tubercle to 
the wax glands. In a great number of aphids a tubercle projects 
out from the sides of the thorax, but always below the wax glands 
when these arc present. In this insect the glands lie below the 
tubercle and consequently on the ventral-lateral side. It is 
quite clear that this waxy secretion would be of the greatest value 
in keeping the insect from getting wet, as it not only projects 
out from the body, but is also powdered over the entire ventral 
portion of the thorax. While walking on the water this secretion 
is always in contact with the surface and serves as a float while 
the insect pushes itself along, moving quite as rapidly as on a 
dry surface. 
In addition to this protection from the water the legs are cov¬ 
ered with a fine pulverulence. This characteristic however is not 
at all peculiar to this species but is found on many other insects. 
On the sides of the seventh and eighth abdominal segments mav 
always be found two tubercles directly above which small hair¬ 
like bristles project. These structures may be of value in deter¬ 
mining the species. The number of sensories on the third joint 
of the antennae seem to be very inconstant, ranging from fourteen 
to eighteen. However, at the base of the unguis there is a fairly 
constant group of six or seven sensories both in the winged and 
wingless forms The color cannot be relied upon as will be shown 
