1966] 
Cooper — Eumenine Wasps 
249 
wasps’ use of water in mixing mortar. Some have suggested that 
the masoning wasp may also use a special fluid from its mouth (e.g., 
Ferton 1921, Hicks 1931). This could be a secretion of its own 
(“saliva”), or possibly substances in solution or suspension which 
are derived from plants or prey and which provide an adhesive agent. 
Perhaps this is so, and excessively hard, masoned nests may indeed 
owe their refractoriness in important part to organic constituents 
provided by the wasp, as Ferton’s (1921) comments seem to suggest. 
If that is the case, proventricular or other fluid used by adult mason 
wasps during emergence from their nests may in turn possess an 
added and complementary emollient, analogous to the cocoon-softener 
claimed for the saw-fly Trichiosoma tibiale which, so far as known, 
is unique within the Hymenoptera (see Hinton 1946). 
Summary 
The larva of Ancistrocerus hatches from the egg by means of 
thoraco-abdominal ruptor ovi, or egg bursters. Development is hyper- 
metamorphic, with a total of five larval instars. Presumably one 
moult (and one instar) has been lost in development, namely that 
moult which sets the strictly prepupal instar apart in phytophagous 
Hymenoptera. Exit from the masoned nest by emerging eumenine 
and masarine wasps involves resoftening the hardened mortar with 
drops of fluid (from the proventriculus in the case of A. antilope). 
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