California Xanthidae— KNUDSEN 
7 
the female. The first pair, the intromittent or- 
gan, is nearly as long as the abdomen. Each 
pleopod consists of three segments: the coxopo- 
dite, basipodite, and flagellum (after Cochran, 
1935: 46). The coxopodite is more or less 
coalesced with the abdominal segments. The 
basipodite and flagellum are closely associated 
and appear as a single unit. Along the median 
margin of the flagellum of the first pair of pleo- 
pods is a canal through which sperm passes, and 
into which is inserted the flagellum of the second 
pleopod. The second pleopod moves up and 
down in the canal during copulation and thus 
serves as a plunger or pump to force sperm 
through the canal. There is an external pair of 
papillae on the coxae of the last pereiopods 
which transfer sperm from the vasa deferentia 
to the intromittent organs. These are perma- 
nently situated in a funnel-shaped opening on 
the anterior side of the basipodite of the intro- 
mittent organs. Thus, during copulation sperm 
is conducted through the vasa deferentia, through 
the external papillae, into the intromittent or- 
gans, and there pumped to the terminal end by 
the second pair of pleopods, and transferred to 
the vulva of the female. 
The internal genitalia of the female are sim- 
ilar to those of the male. There is a pair of 
ovaries (Fig. 1, B and C) which are U-shaped 
and lie over the liver anteriorly, and below the 
heart posteriorly. They unite just behind the 
dorsal side of the stomach where they give rise 
to a pair of oviducts. Each oviduct enlarges into 
a spermatheca as it passes ventrally, narrows 
again, and terminates in a vulva which opens 
on the sixth thoracic sternite (Fig. 2, B). 
Mating Posture , Time , and Frequency 
The writer had occasion to see pairs of Para- 
xanthias taylori and of Lopbopanopeus bellus 
diegensis in copulation on 12 different occasions 
in the laboratory. On one of these occasions the 
entire act was witnessed. There is no prenuptial 
pairing or courting in the Xanthidae as reported 
for other crabs by Williamson (1903: 101), 
Hay (1904: 405), and Churchill (1918: 105). 
The writer has seen the courting of Cancer an- 
tennarius on four occasions in the field. During 
the prenuptial pairing the male of this species 
carries the slightly smaller female around in his 
chelae. When disturbed he runs to a hiding place 
with the female tightly in his grasp. If sepa- 
rated the female is very passive and will offer 
no defense. The male "courts” the female until 
she completes ecdysis, at which time they copu- 
late. Two mating pairs of this species were 
found at Palos Verdes in which the female was 
completely soft, having just molted. In each in- 
tance the crabs were in copulation. 
The California Xanthidae breed while in a 
hard-shell state, and not after molting. The one 
complete act observed progressed as follows: A 
male Paraxanthias taylori approached a female 
of this species. The female raised her chelae, 
which were grasped by the male’s chelae, and 
was lifted above the substratum. Without break- 
ing stride the male pushed the female over back- 
wards and proceeded to straddle her body. The 
male then lowered his abdomen, catching the 
female’s abdomen with it as he did so. By ex- 
tending his abdomen under hers, he forced the 
female to open her abdomen away from her 
body and thus expose the vulvae. The intro- 
mittent organs were lowered automatically with 
the male’s abdomen and were quickly inserted 
into the vulvae. 
In the laboratory, xanthid crabs were seen in 
copulation for periods up to 3 hours. The male 
was always dorsal to the female, which is a posi- 
tion typical for most Brachyura, but is unlike 
that of Pachygrapsus eras sipes (Hiatt, 1948: 
199). Copulation was often repeated by one 
pair of crabs on several successive days. Forty 
per cent of the ovigerous females examined had 
full or partially full spermathecae, which sug- 
gests that copulation may not be required for 
each batch of eggs. 
Reproductive Season 
There is considerable variation among the 
major genera of the California Xanthidae in the 
duration of their reproductive seasons. The 
writer has observed ovigerous females of Lopho- 
panopeus l. leucomanus and of L. bellus diegen- 
sis collected from February to October inclusive. 
Paraxanthias taylori has the next longest season, 
with ovigerous females common from April to 
September. Cycloxanthops novemdentatus does 
not become ovigerous until the middle part of 
June. Females of this species were collected with 
