244 
Psyche 
[December 
that still cling to the larva’s abdomen. For this and other reasons 
the only exuvium ordinarily found in the pupal cell of a wasp is that 
of the terminal larval moult. Accordingly there are three conditions 
that must be satisfied for a direct demonstration of the number of 
instars : ( i ) the first instar larva must be identified with certainty, 
generally by witnessing hatching, (2) exuvia must be removed when 
shed, or very shortly thereafter, and (3) closely and appropriately 
spaced observations must be continued from hatching to the emer- 
gence of the imago. 
These conditions have been met for 16 individuals of A. antilope 
reared in isolation chambers on the original prey with which each 
was provided by its mother. In every case the full number of moults 
was six. The first four moults mark the limits of the first four larval 
stages, which are devoted solely to feeding and growth. The fifth 
stage larva, unlike the earlier four, does not moult to a feeding in- 
dividual. It completes feeding, cleans and “varnishes” its cell, gen- 
erally disposing of any exuvia that may remain, spins a cocoon (which 
may be incomplete in A. antilope ), passes its meconium, and becomes 
a quiescent prepupa (or “mature larva”). If of the spring brood, the 
fifth larval moult generally occurs about 3.5 to 4.5 days after the 
meconium has been voided, releasing the pupa which is the sixth in- 
star. The fifth instar larva of the summer brood diapauses after 
passing the meconium, and only in the following spring does the 
fifth moult occur. The final, or sixth moult, occurs after the pupa 
has become fully colored, and it is that final moult which frees the 
imago within its cocoon. The approximate times at which each of 
the first five moults occurs after hatching, and the average durations 
of each instar (at a temperature from 20°C to 28°C) are given in 
table 1 ; the fifth moult is there recorded for first (spring) brood 
individuals only, for that of members of the summer brood occurs 
in the following spring some 8 months or so after the onset of dia- 
pause. It should be noted that the egg stage is considered to have 
ended when the developed larva commences to cut its way out of 
Table 1 (see text for explanation) 
Occurrence of: 
on day 
duration of: 
days 
hatching 
O 
egg stage 
2.5 + 
ecdysis-i 
3.2 
instar- 1 
0.7 
ecdysis-2 
4.0 
instar-2 
0.8 
ecdysis-3 
5.0 
instar-3 
1.0 
ecdysis-4 
6.3 
instar-4 
1-3 
ecdysis-5 
17 
instar- 5 
10.7 
ecdysis-6 
29-36 
pupa 
12-19 
