
698 THE AMERICAN NATURALIST.  [Vor. XXXVI. 
of the fused glossa (g/.), short but distinct flaplike paraglossae 
(pg.), three-segmented palpi (/.f.) borne on a long palpiger, 
and at the base a distinct mentum (s.) and submentum (sm.). 
| As with the digger wasp, 
the developing head of the 
imago, with its long 
antennz and mouth parts, 
demands more space than 
is afforded within the lar- 
val head segment, so that 
it is crowded backward and 
occupies part of the first 
and second larval thoracic 
segments. But the form- 
ing imaginal mouth parts 
are to be found with their 
tips projecting into the 
corresponding larval parts, 

imd., imaginal mandible; Zx., larval maxilla; 
i.mx., imaginal maxilla; ZZi., larval labium; ZZ, as shown in Fig. I8. The 
imaginal labium avt 
conditions of the develop- 
ment of the imaginal parts, and of their perfect correspondence 
with the larval parts, are wholly like those already explained 
for the digger wasp. 
DIPTERA. ` 
In the case of the Diptera, — and it is here that the neces- 
sity of ontogenetic study is most important, indispensable 
indeed, for the determination of the homologies, — we have, 
as in the Hymenoptera and Lepidoptera, a great variety of 
mouth-part conditions culminating in the extreme specialization 
characteristic of the muscid forms. In most Diptera it is 
obvious that a total reduction of at least one pair of the buccal 
appendages has occurred, with a large reduction and complete 
modification of the remaining parts. From a considerable 
study of the anatomy of the fully developed mouth parts in a 
long series of dipterous forms, including representatives of all 
except one (the Ornephilidze) of the nematocerous families, — 
