Shell Selection of Hermit Crabs — O rians and King 
301 
TABLE 2 
Shell Utilization by Hermit Crabs at Horseshoe Cove, California 
SHELL SPECIES 
P. hirsutius cuius 
P. 
samuelis 
P. granosimanus 
No. 
% 
No. 
% 
No. 
% 
Thais emarginata 
271 
50.9 
48 
3.9 
44 
21.6 
Tegula brunnea 
18 
3.4 
116 
9.5 
49 
24.0 
Tegula funebralis 
53 
10.0 
722 
59.0 
37 
18.1 
Calliostoma costatum 
53 
10.0 
297 
24.3 
13 
6.4 
Littorina planaxis 
72 
13.5 
18 
1.5 
2 
1.0 
Other 
65 
12.2 
22 
1.8 
59 
28.9 
Total 
532 
1223 
204 
All samples of Diogenes gardineri are uniform 
in their shell utilization, that is, the overlap in 
shells used is greater than 60% in each case. 
Similarly, Dardanus scutellatus is homogeneous 
when compared with itself. The trellis diagram 
indicates that sample F-4 of Calcinus latens 
differs from all other samples of the same species, 
but no significance may be attached to it, since 
only four individuals of this species were ob- 
tained in sample F-4. 
There is very little overlap ( < 30% ) in the 
species of shells utilized by Diogenes gardineri 
and Dardanus scutellatus. With the exception 
of the F-4 sample of Calcinus latens discussed 
above, there is little overlap between Dardanus 
scutellatus and Calcinus latens, but the similarity 
is greater than between Diogenes gardineri and 
Dardanus scutellatus. 
It is evident from the diagram that Diogenes 
gardineri and Calcinus latens are very similar 
in their shell requirements ( > 60% overlap, 
with the exception of the F-4 sample of Calcinus 
latens ), even though different samples of the 
shells utilized by Diogenes gardineri resemble 
each other, and different shell samples of Cal- 
cinus latens resemble each other more than the 
samples of Diogenes gardineri resemble samples 
of Calcinus latens. 
The overlap in the Californian samples be- 
tween Pagurus hirsutius cuius and P. samuelis 
was 30%; between P. hirsutius cuius and P. 
granosimanus, 46%; between P. samuelis and 
P. granosimanus , 40%. 
Shell utilization is basically dependent upon 
the availability of shells and the morphological 
limitations of the individual hermit crab. Thus 
the shells which are available, and hence utilized, 
by Pagurus samuelis in northern California as 
determined in the present study, are markedly 
different from those utilized by the same species 
in southern California (Coffin, 1954). Similarly, 
it is not to be inferred that the differences in 
shell utilization of the three Eniwetok pagurids 
are due to preferences of the species. The dis- 
tinct differences may be explained on the sim- 
pler basis of differences in crab size. Dardanus 
scutellatus, which differs most markedly from 
the other two species in shell utilization, is also 
markedly larger (with average wet weight of 
0.81 g) than both Calcinus latens (0.07 g) 
and Diogenes gardineri ( 0.04 g ) . As might be 
expected, Calcinus latens and Diogenes gardi- 
neri, which are similar in shell utilization, are 
also similar in size. 
Shells may also be selected as a function of 
species-specific,, preferences and social interac- 
tions as discussed in the next section, but data 
of this type are not available for the Eniwetok 
hermit crabs. 
EXPERIMENTS 
To test the possibility of active shell selection, 
crabs were taken from Horseshoe Cove and 
subjected to the following types of experiments 
in the laboratory: (1) A single crab was given 
a choice of several shells of different species; 
( 2 ) crabs of two or more species were presented 
with a single unoccupied shell. 
Experimental crabs were removed from their 
shells by the application of a lighted match to 
the posterior portion of the shell. When the 
crab relinquished its hold it was placed in a 
shallow petri dish with the unoccupied shells. 
Pagurus hirsutius cuius consistently preferred 
