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PACIFIC SCIENCE, Vol. XII, October, 1958 
75 mm. is reached that this large elliptical 
region is bright yellow, free or nearly so of 
scales with dusky centers. The green on the 
caudal fin also intensifies and blue appears 
posterior to the crescent and on the outer 
part of the dorsal and anal fins. On large fish 
(the species is the largest of the genus, at- 
taining a standard length slightly in excess of 
100 mm.) a suffusion of dark blue becomes 
apparent anteriorly. 
A 98 mm. specimen speared in Moorea 
provided the following color description: 
body black except for a broad yellow area 
posteriorly, the forward end of which is 
rounded and reaches a vertical through base of 
fourth soft ray of dorsal fin; head dark blue 
and lacking the prominent black lateral band; 
lips dark blue, shading to light blue on inner 
surfaces; caudal fin with a subterminal black 
crescent, bright green anterior to and blue 
posterior to this marking; dorsal and anal fins 
black with broad light blue edges; pectorals 
hyaline; pel vies black. 
This specimen and another 94 mm. one 
with the same color are males. On other indi- 
dividuals as large as blue-headed ones seen 
underwater the dark midlateral band is visible 
on the head and the deep-blue color is lack- 
ing, although the head and anterior part of 
the body above and below the band are dark 
grayish blue. The largest of the latter color 
variety collected in the Society Islands is 
80 mm. in standard length, and it is a female. 
It is believed that others may consistently 
prove to be females too. At times one of each 
color variety are seen together as a pair. The 
above-mentioned color differences, if con- 
clusively demonstrated to be sexual, are slight 
compared to the degree of sexual dichroma- 
tism known in some of the Labridae (Randall, 
19554- 
On numerous occasions in the Society 
Islands and Tuamotus individuals of this 
species, both juvenile and adult, have been 
observed picking at the bodies, heads, and 
fins of other fishes. The contents of the gut of 
eight specimens, 60 to 98 mm. in standard 
length, have been examined. Four were empty 
save for a mucuslike substance and, in the 
case of two of the specimens, tiny digenetic 
flukes in the intestine, which were probably 
internal parasites of these fish. A 69 mm. 
specimen had two calagoid copepods and one 
fish scale in the stomach; 65 and 80 mm. 
specimens were empty except for a few fish 
scales in the stomach and intestine. The 
stomach of a 60 mm. specimen was empty, 
but three small larval isopods of the family 
Gnathiidae (larvae of this family consist ex- 
clusively of fish parasites) were found in the 
intestine. 
The presence of fish scales in the gut is 
comprehensible when the stout, curved, ca- 
nine teeth and the vigor with which the little 
labrids nip the host fishes are considered. A 
medium-sized L. bicolor was seen to actually 
lift a piece of skin of an adult puffer, Arothron 
meleagris Bloch and Schneider, into a pro- 
nounced peak in its apparent effort to dis- 
lodge an ectoparasite. 
The host fishes do not always tolerate such 
ardent pecking. Often they move their bodies 
sharply or swim away when the pecking 
becomes vigorous. 
Adult L. bicolor do not display the oscil- 
latory swimming movement as previously 
described for L. dimidiatus. The brilliant yel- 
low and black young do, however. A further 
distinction between the behavior of young 
and adults lies in the tendency of the former 
to remain in a very restricted region, fre- 
quently a small cave or under a ledge. Adults 
are almost constantly on the move and appear 
to cover a larger area than other species of 
Labroides. Still, they seem to remain in the 
same general region. In addition to seeing 
what appeared to be the same individuals day 
after day at a certain reef, several which were 
wounded with a spear and could be positively 
identified were repeatedly sighted at approxi- 
mately the same place. 
As might be surmised from the above, 
adults of this species are more prone to seek 
out fishes from which to remove parasites 
