2 CLASSIFICATION OF THE ALEYEODID^. 



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 Aleyrodidap^ 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 ALEYBODID^. 



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. Gary, in his work on embryol- 

 ogy/ * 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 certainlj^, 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 alcyrodids, possess 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 the setse 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 Keaumur 

 in 1736, whose interesting observation we here quote.- 



Pour y parvenir, & pour avoir Thistoire de uotre petit papillon, le 25. Juin je 

 choisis une feuille sur laquelle il y en avoit un seul tres-tranquille. & que je 



"The small figxires refer to the " Literature," page 97. 



