2 CLASSIFICATION OF THE ALEYRODIOE. 
accurately as possible a system of classification based upon the natural 
relationship of the various forms. 
The present paper deals with certain features of the anatomy and 
external structure of the Aleyrodidae : and attempts to show the 
position of the family among homopterous insects. All species of 
the family at present known are treated, save those belonging to 
Aleyrodes, and this genus will be made the subject of a later pub- 
lication. 
It is hoped by the writers that this paper will facilitate the classi- 
cation of these insects and further stimulate the interest already 
evidenced in them. 
MORPHOLOGY OF THE ALEYRODIDiE. 
THE EGG. 
The eggs of insects belonging to this family are elongate-oval in 
shape and are smooth on the surface or variously sculptured. This 
egg marking is often one of the simplest means of distinguishing be- 
tween two closely allied species. The eggs are provided at or near 
their larger end with a stalk which, in such species as Aleurodicus 
holmesii, is extremely long. (PI. XIX, fig. 6.) It serves as an at- 
tachment for the egg, but it also seems to direct the spermatozoa at 
the time of fertilization. At this time the stalk is filled with proto- 
plasm and the mycropylar structure is plainly visible within the egg 
just at its entrance. After fertilization this protoplasm dries up 
and the stalk becomes a hollow tube. Cary, in his work on embryol- 
ogy, 1 ° arrives at a similar conclusion, for he says : 
The spermatozoan moves up through the protoplasm contained in the stalk 
of the egg, while the female pronucleus moves down and comes to lie at the 
entrance of the stalk. Immediately after the act of fertilization the proto- 
plasmic contents of the stalk shrivel and dry up. 
If, however, the primary function of this stalk is for the direction 
of the spermatozoa, it is strange that there should be such great varia- 
tion in its length. It is certainly, however, not comparable to the 
protective stalk in eggs of such forms as Chrysopa, for it is not a 
waxy secretion but an extension of the chorion. The eggs of some 
psyllids, which are closely related to the aleyn 3S stalks, 
but their exact function is unknown to us. 
The arrangement of the eggs upon the leaf varies greatly with 
different species. The females of some insert tin' Beta into the tis- 
sues and, using the rostrum as center and the body as radius, place 
the eggs in regular circles. This habit was first noticed by Reaumur 
in L736, whose interesting observation we here quote. 2 
pour >• parvenir, & pour avoir l'hlstoire de aotre petit paplllon, le 25. Juin je 
Choisis unc feillUe sur l.-upiHlo il y on avoli un soul tivs-tranquille, & que je 
• The small Bgurei refer to the " Literature," page 97. 
