
No. 429.] THE MOUTH PARTS OF INSECTS. 693 
distinct and readily recognizable mandibles (zzd.), maxillze (zzx.) 
with short but distinct three-segmented palpi (mx.f.), and 
labium (/.) with very small ex-articulate palpi. 
If an old larva, nearly ready to pupate, be taken, and its 
head dissected, as illustrated in Fig. 11, it will be found that 
underneath, or within, the larval labium, 
or labial cuticle, will be found the form- 
ing imaginal labial palpi ; within the lar- 
val maxilla will be found the forming 
imaginal maxilla, while within the larval 
mandible will be found nothing at all. 
In Fig. 11 the larval cuticle of the left 
side of the head has been dissected away, 
showing this correspondence between 
larval and imaginal parts; the larval max- 
illary sheath has been slipped off of the 
forming imaginal maxillar process, while 
on that part of the forming imaginal head 
from which the larval mandible was taken 
there is not a trace even of a forming 
organ. Fig. 12 
shows the entirely 
dissected-out 
pupal (equals subimaginal head), with the 
already unmistakably recognizable imagi- 
nal mouth parts. 
Thus in this representative of the 
Lepidoptera we find the imaginal mouth 
parts developing in perfect correspond- 
ence with the larval parts, imaginal 
maxillae within larval maxilla, imaginal 
labium in larval labium, and within the 
well-developed larval mandibles nothing, with a corresponding 
- total absence of mandibles in the fully developed moth. By 
sectioning the heads of old larvz, it is readily perceivable that 
these developing imaginal mouth parts lying within and corre- 
sponding to the various larval parts are evaginations of the new 
or imaginal derm which forms a continuous layer underneath the 

i.7:x., imaginal maxilla 

maxilla 
labial palpus; ant., Koi 
