190 AN ESSAY ON THE DEVELOPMENT 
ever, the lower ring is complete—7. ¢., the two halves of the stipes have become 
united. That it must be stipes is shown by the fact that it bears the palpus, and 
again the surmounting sclerite must be maxillary also. 
There are other species allied to those already cited in which similar structures 
occur; but I need for the present call attention to only one more; a species of Olfersia 
(Pl. I, Fig. 19). Here the ring is complete in front, but broadly open behind, and 
bears the chunky, single-jointed palpus. Surmounting is a single sclerite, very much 
resembling in appearance that of Pteromalus, and undoubtedly homologous with it. 
Of course Olfersia is parasitic in habit, and the mouth parts are specialized for blood- 
sucking ; but the sclerites composing them are nevertheless derived from the same 
source as in the “higher ” types. 
I have several times referred incidentally to Simulium, and of this the galear 
structures are figured (PI. I, Fig. 1"). Dissecting the parts out carefully we find an 
almost complete ring at the base, the stipes, to which the palpus and palpifer are 
attached. Surmounting this is a pair of sclerites, each almost a half cylinder, repre- 
senting the subgalea, and bearing the two-jointed galea. Here again I claim that the 
three joints just referred to must be maxillary because they are directly articulated to 
the sclerite bearing the maxillary palpi, and the labial structures are all shown at 
loiee, 1, 
A step in the direction of union we find in the Anglesea gnat or midge—also a 
Simulid, to which reference has been already made. Here we see (PI. I, Fig. 2") the 
subgalea united most of their length at one side, while the galear joints are yet free. 
The basal stipes is not figured because none of my specimens showed it clearly ; but 
the palpifer, palpus and lacinia, as they are connected with it, are shown in the 
specimen. 
In the Aszlidew we find another suggestive structure, studied in the light of the 
facts already set out. Here we see, as illustrated Pl. IL, Figs. 1* and 1’, the basal 
stipes well developed, united posteriorly, but separated in front. The palpifer and its 
attached palpus are situated at the sides, clearly articulated to the stipes, whose char- 
acter is thus fixed. Attached to this stipes is a broad, infolded structure, united be- 
hind but open in front; maxillary because of its attachment to the stipes, and sub- 
galea from its location. It bears in orderly sequence the two-jointed galea of which 
the terminal joints are free. The species of the Asiléde are large and easily dissected, 
and the figures were drawn from a species of Laphria. The attachments are but 
little different in the species, and as the figures illustrate the structure from both 
front and rear, the position of the joints should be clear. These figures will be again 
referred to in another connection. 
