14 
PACIFIC SCIENCE, VoL XX, January 1966 
Only a single Stage IV crab was observed 
undergoing ecdysis. A 10% increase in carapace 
width occurred during this moult. The abdomen 
of the new instar (Stage V) increased 34% over 
that of the original Stage IV crab. Assuming 
this single observed moult to be typical of all 
Stage IV crabs, this is a considerable reduction 
in abdomen increase compared to the Stage III— 
IV moult. Following this moult (Stage IV-V) 
the abdomen is, for the first time, either as wide 
or wider than the carapace, and the definitive 
adult, Stage V female is attained. 
Future ecdysis in the Stage V crabs is largely 
a matter of increase in size and not an alteration 
of morphological characters. The average in- 
crease in carapace size with each moult of the 
stage is 9% (in 33 individuals). The abdomen 
increases an average of 13.1%. It was noted that, 
as is the case when all stages are considered, the 
smaller Stage V crabs showed proportionately 
larger increases than did the larger crabs (greater 
than 10 mm) of this stage. 
The pre- and posthard stages of F. subqua- 
drata require only three or four days before an 
apparently normal exoskeleton consistency is 
reached following ecdysis. However, more recent 
work (Pearce, 1962b) on related species indi- 
cates that, while external appearances suggest a 
"normal” intermoult condition, the actual de- 
position of new endocuticular lamellae continues 
for several weeks. The exoskeleton of the hard 
Stage I crabs requires somewhat longer for the 
integument to become completely hardened. 
Three weeks were required by one individual 
before the carapace was completely calcified and 
rigid. This could be due to the fact that the ani- 
mal was kept in an artificial environment in 
which the normal parameters were not present. 
Hiatt (1948:163) conclusively demonstrated 
that changes concomitant with the moulting of 
P. crassipes are affected by prolonged laboratory 
conditions. 
In no case was any self- or exuvial mutilation 
observed, such as was noted in P. crassipes by 
Hiatt (1948:158) and in the xanthid crabs by 
Knudsen ( 1957 : 140 ) . 
Moulting was most frequent during the 
summer months, particularly during early and 
fmamjjasondj fm 
1959 I960 
12 
I i 
£ 
> 
I 0 H 
m 
jo 
— ( 
9 m 
2 
TJ 
m 
jo 
8 > 
c 
JO 
m 
7 
o 
6 
Fig. 2. Curves showing: dash line, surface water temperatures taken in the San Juan Archipelago during 
1959 and early I960; solid line, per cent of Stage V crabs in ecdysis during the period from February, 1959 
to March, I960. 
