Biology of Pachygrapsus crassipes — Hi ATT 
149 
but the supplementary stages which are diag¬ 
nosed in the initial portion of the intermolt 
cycle by differential sclerotization of the integu¬ 
ment vary with the shape of the carapace of 
the crabs concerned. The curvature and thick¬ 
ness of the carapace differ for each species, 
hence, each must be studied individually to 
determine the adaptability for any standardized 
series of intermolt stages. This procedure was 
followed in the present study; the sequence of 
sclerotization is shown in Table 2. It was noted 
that differences between these data and those 
presented by Drach (1939) for M. squinado 
were slight; consequently only slight modifica¬ 
tion was necessary to adjust the criteria involved 
in designating comparable stadia. This succes¬ 
sion of rigidity in the various areas of the 
integument was found to be constant regardless 
of the size of the animal or the temperature 
of the water. 
TABLE 2 
Summary of Post-exuvial Sclerotization and Loss of Flexibility in Various Integumental 
Regions of a Specimen of P . crassipes with a Carapace Breadth of 28.5 Millimeters. Signs: 44 , 
Integument Completely Soft; +, Integument Partially Rigid but Easily Depressed; —, Integu¬ 
ment Completely Rigid. 
DAYS 
AFTER 
MOLT 
CARAPACE 
THORACIC 
STERNITES 
CARPUS AND 
PROPODUS OF 
CHELAE 
MERUSAND 
CARPUS OF 
WALKING LEGS 
STAGE 
Proto- 
gastric 
Area 
Meso- and 
(Jrogastric 
Area 
Anterior 
Branchial 
Area 
Posterior 
Branchial 
Area 
Branchio- 
stegites 
Cardiac 
Area 
1 
44 
44 
44 
44 
44 
44 
44 
44 
44 
Ai 
2 
4 
44 
44 
44 
44 
44 
44 
44 
44 
Aa 
3 
4 
44 
44 
44 
44 
44 
44 
44 
44 
Aa 
4 
— 
44 
44 
44 
44 
44 
44 
4 
44 
Aa 
5 
— 
44 
44 
44 
4-+ 
44 
44 
4 
44 
Aa 
6 
— 
4 
4 
44 
44 
44 
44 
4 
44 
Bi 
7 
— 
4 
4 
44 
44 
44 
44 
4 
44 
Bt 
8 
— 
4 
4 
44 
44 
44 
44 
4 
44 
Bx 
9 
— 
4 
4 
44 
44 
44 
4 
4 
44 
Bx 
10 
■— 
4 
4 
44 
44 
44 
4 
44 
Ba 
11 
— 
4 
4 
44 
44 
44 
4 
— 
44 
Ba 
12 
— 
4 
4 
44 
44 
44 
4 
— 
44 
Ba 
13 
— 
— 
4 
4 
44 
44 
4 
—. 
44 
Cx 
14 
— 
— 
— 
4 
4 
4 
4 
— 
44 
Cx 
15 
— 
— 
— 
4 
4 
4 
4 
— 
44 
Cx 
16 
— 
— 
— 
4 
4 
4 
— 
44 
Cx 
17 
— 
— 
— 
4 
4 
4 
— 
— 
4 
Cx 
18 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
19 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
20 
—• 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
21 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
22 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
23 
— 
—- 
— 
— 
4 
4 
— 
— 
4 
Ca 
24 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
25 
— 
—■ 
— 
—. 
4 
4 
•— 
— 
4 
Ca 
26 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
27 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
28 
— 
__ 
— 
— 
4 
4 
— 
— 
4 
Ca 
29 
—- 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
30 
— 
— 
— 
— 
4 
4 
— 
•— 
4 
Ca 
31 
— 
— 
— 
■— 
4 
4 
— 
— 
4 
Ca 
32 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
33 
— 
— 
— 
— 
4 
4 
— 
— 
4 
Ca 
34 
— 
— 
— 
— 
— 
— 
— 
— 
— 
Cs 
