14 CLASSIFICATION OF THE ALEYRODIME. 
Psyllidse have a prominent bilobed pulvillus, while the Aphididse 
have practically none. In some forms in the Aleyrodinse the paro- 
nychium is very prominent, and in all forms it is represented either 
by a pad or a spinelike structure. The paronychium in the Aleyro- 
didas, however, is never bilobed as in the Psyllidge, though in some 
species there is a slight indication of this. 
WAX PORES OF PUPA CASE. 
The secretion of wax is very common in many of the Homoptera 
and is particularly noticeable in the families related to the Aleyro- 
didse, namely, Psyllida?, Aphidida?, and Coccidie. In the Psyllidae 
besides the arial wax glands there are in the larva: of many species 
abdominal and marginal wax glands, the marginal ones of which 
secrete long, fine, hollow, brittle, waxen hairs, which form a fringe 
about the insect. In the Aphididse the glands are usually grouped. 
In Schizoneura and some species of Pemphigus the secreting cells are 
arranged in rings, while in C henries, Mindarius, etc., they are agglom- 
erate in nature, and in some forms these agglomerate pores are sur- 
rounded by a chitinized ring. 
In the larva? of the Aleyrodidse we have three types of pores, 
namely, simple, agglomerate, and compound. In the Aleyrodime 
the dorsal pores present are all simple, though many of them may be 
larger than others and arranged in definite rows, producing a fringe 
comparable to that in the larvae of the Psyllidae. It is in the Aleurodi- 
cinae that the development of special wax secreting structures is found 
and this development seems to throw some light on the relation of 
the forms. In Dialeurodieus the dorsal pores are simple and usually 
scattered, though in silvestril the greater number of them are col- 
lected into a subdorsal band. In the species lahillei these simple 
pores have taken on a definite and restricted arrangement, forming 
agglomerate pores as in some Aphidicloc. In the center of some of 
these, however, is found a large, chitinous process which points to 
these as near the forerunners of the true compound pores in 4 ! lew 
cue. This fact, together with the shape of the lingula, wing, etc.. 
seems to indicate that lahillei is the type of a new genus older than 
Aleurodicue, but not so old as Dialeurodicus. In Aleurodicus the 
compound pores have a constant structure in all (he species, indicated 
in Plate III, figure 2. The chitinous ring surrounding the agglom- 
erate pores in some other forms is here a definite elevated cup-like 
structure. Within this cup the spinnerets are arranged in a ring 
similar to the ring in Schizoneura, but, unlike these cells, are pro- 
duced into more or l< 38 elevated rods or tubes. Within this: ring of 
Bpinnerei rods is a chitinous process, apparently hollow, which may 
he very long, :is in holmesii, or as short as the outer cup. In /'(/ralcy- 
rodc* : while the pore is of the same compound type, it is different in 
