466 MAUD D. HAVILAND 
opening on the floor of the mouth under the U-shaped hypo- 
pharynx. 
The mid-gut is shut off from the oesophagus by a valve. 
The former, which is greatly distended, is lined with flattened 
polyhedral cells with large nuclei. As in other hymenopterous 
larvae at this stage there is no communication between the 
TEXT-FIG. 9. 
Texr-Fic. 10. 
Fig. 9.—The full-grown larva. x 35. 
Fig. 10.—Head of full-grown larva. x 100. lab. = labium; lbr. = 
labrum; md. = mandible: ma. = maxilla; sal. d. = salivary duct. 
mesenteron and proctodaeum. The structure of the latter 
merits description. In larvae of the first and second instars the 
lumen is wide, and lined with a columnar epithelium of hyper- 
trophied hypoderm cells with conspicuous nuclei. As develop- 
ment proceeds the anus becomes proportionately smaller, 
and an outgrowth from the antero-ventral wall of the procto- 
daeum projects backwards into the lumen. ‘his outgrowth 
is shaped like a shovel, shortest on its dorsal aspect, and has 
