534 Cc. H. RICHARDSON 
a distinctly Cynipoid type, since nothing like it has been observed 
in other forms. 
There may be as many as four or as few as two larval stages 
in the development of the Hymenoptera in which hypermeta- 
morphosis occurs. In general, as development proceeds the suc- 
cessive larval stages become less and less modified externally 
and more and more specialized internally. An exception to this 
rule, however, is seen in Polynema sp., in which the first larval 
stage is highly generalized and the greatest modification aswell 
as internal specialization occurs in the last or modified hymenop- 
teriform stage. 
The end result of hypermetamorphosis is a larva resembling 
in external structure the common type found throughout the 
order, the hymenopteriform larva. The most extreme devia- 
tions from this type are found in Polynema, as noted above and 
in Perilampus, Orasema and Spalangia which have curious tuber- 
culate hymenopteriform larvae. 
Table 1 shows the distribution of the different larval types 
and the subsequent stages into which they develop before pupa- 
tion. 
HYPERMETAMORPHOSIS IN SPALANGIA MUSCIDARUM 
The egg of Spalangia muscidarum hatches in the insectary in 
from two to three days. It is doubtful whether this represents 
the normal time of hatching, for the warm, moist natural habitat 
of the larval stages, that is, the manure heap, would undoubtedly 
bring about a greater rapidity of development than ordinary 
experimental conditions permit. Three quite distinct larval 
forms were found, first the minute planidium, second a larger 
atracheate larva and third and last a still larger tracheate larva. 
THE PLANIDIUM LARVA 
This larva is about 0.5 to 0.7 mm. long, its greatest width 
being about 33 per cent of the length. In color it is dull white, 
the region of the mesenteron showing as a median dark area. 
Thirteen segments are visible of which the anterior two are 
largest. The anterior segment bears a pair of short antennal 
