16 
PACIFIC SCIENCE, Vol. XVIII, January 1964 
of Hemigrapsus, Lophopanopeus, and Petrolis- 
thes were subjected to these artificial environ- 
mental changes. In comparing the life histories 
of Hemigrapsus oregonensis and H. nudus sev- 
eral events notably occur just after significant 
changes in photo-period or temperature have 
occurred. Namely, in H. nudus ( Fig. 1 ) copula- 
tion begins at about the shortest day in the year 
and progresses steadily as the photo-period 
lengthens. However, in this cycle there is no 
correlation with temperature, as the temperature 
has slowly been decreasing prior to the onset of 
copulation and after the period of copulation. 
At the end of this reproductive cycle the tem- 
perature is still somewhat on the rise, but the 
photo-period has again reached its peak and the 
days begin a shortening trend at the time when 
the last of the larvae hatch. It is conjecture to 
do more than suggest that there may be some 
correlation between the life cycle and this trend 
from the shortest photo-period to the longest 
photo-period. On the other hand, the life cycle 
of H. oregonensis (Fig. 4) seems to parallel 
the trend of temperature with reference to egg 
deposition and the maintenance of the first and 
second broods. That is, egg deposition of the 
first brood begins rapidly after temperatures 
start to rise in March, and the second brood 
does not complete hatching until temperature 
has reached its peak and has begun a downward 
trend. The exact time at which copulation is 
most prevalent for this latter species is not well 
known and hence this event cannot be paralleled 
with photo-period or temperature. In both spe- 
cies the seeming correlation between environ- 
mental factors and reproductive activity failed 
to account for the onset of spermatogenesis or 
oogenesis. It is quite possible that the original 
triggering stimulus was received during the 
summer or fall prior to oogenesis and sperma- 
togenesis, and that subsequent reproductive be- 
havior simply followed as a chain reaction 
probably triggered by hormone activity. That 
hormones are important is clearly seen in the 
data given for H. oregonensis, where it is noted 
that some probable chemical stimulus caused 
males to mate only with certain females and to 
ignore all others. The striking difference be- 
tween the two species of Hemigrapsus suggests, 
however, that different external stimuli may be 
influencing the onset of reproduction in these 
two species. Because of original mistiming of 
experimentation, which was based on repro- 
ductive activity as recorded in the literature, and 
a series of mechanical difficulties in cooling 
and lighting devices, our data are incomplete 
and inconclusive in this aspect of research. Thus, 
we will reserve this problem for later research 
and publication. 
family XANTHIDAE 
Lophopanopeus bellus bellus 
HABITAT: The pebble crab, Lophopanopeus 
bellus bellus, is replaced in the south by its 
counterpart, L. bellus diegensis. As shown by 
Knudsen (1960:171) this species differs from 
the Lophopanopeus complex of leucomanus in 
that it prefers the more quiet water of bays or 
estuaries to the open ocean shores. The writer 
finds L. b. bellus occupying a micro-habitat 
identical to that of L. b. diegensis in the south. 
The former subspecies is found in Puget Sound 
at the lower extremes of the intertidal zone and 
seems to prefer a situation where a single layer 
of rock covers fine sand or mud. Rocks which 
do not fit closely to the substrate, but leave a 
slight gap underneath, are less frequently oc- 
cupied by this crab. On the other hand, this 
species burrows well back under large rocks that 
hold so firmly to the substrate that hydrogen- 
sulfide mud is produced. Like the southern sub- 
species, the Puget Sound form often "plays dead" 
for a few minutes when disturbed in its hiding 
place. Way (1917:367) states that this crab 
is always found with Cancer oregonensis buried 
in sand and mud under rocks on rocky shores. 
Around Titlow Beach and Point Defiance the 
two species often occur together but Cancer 
oregonensis is also found higher up in the inter- 
tidal zone. Our collecting records indicate that 
not all rocky shores are suitable for Lopho- 
panopeus. In all cases where this crab is found 
there is a noticeable water current, though often 
not strong, during the ebb and flow of the tide. 
The presence of a tidal current is the only factor 
that the present writer finds to separate the 
Lophopanopeus habitat from almost identical, 
adjacent stretches of beach where Lophopan- 
opeus is not present. 
FEEDING HABITS: Stomach analyses were made 
for seven individuals. The nature of the ma- 
