Review of Labroides — Randall 
339 
upper lip) and a median lateral black band 
running posteriorly from lower corner of up- 
per lip and tips of lobes of lower lip through 
eye to merge with black posterior part of 
body; dorsal and anal fins pale (light blue in 
life), except for basal part of spinous portion 
of dorsal fin which is black (this color con- 
tinuous with that of median dorsal black 
band) and a narrow horizontal dark line ex- 
tending from ends of last few dorsal spines 
posteriorly into the anterior half of the soft 
portion of the fin about three-fourths the 
distance from the base of the fin; paired fins 
pale. The body of the 18.8 mm. juvenile 
specimen is black except for a broad light- 
brown band along the back, this band con- 
tinuing on to top of caudal fin; the remainder 
of the caudal fin is black like the body except 
for lower distal corner which is pale; the head 
is brown with median dorsal and median 
lateral black bands. In life the band along the 
dorsal part of the head and body is bright 
purple. No yellow color is visible on juve- 
niles. The first indication of the yellow colora- 
tion is a suffusion of tan over the head and 
anterior part of the body. This occurs at a 
length of about 50 mm. (based on estimates 
of the size of individuals seen underwater). 
Labroides phthirophagus is known only from 
the Hawaiian Islands, where it is a common 
species. That it escaped being described in 
Jordan and Evermann’s time is probably due 
mainly to its small size. It is too small to be 
caught in the usual fish traps or hook and 
line. An indication of its abundance is its 
listing [as L. dimidiatus by Brock (1954: 307)] 
among the species consistently tabulated in 
his underwater transects of Hawaiian reef 
fishes. 
The record of Labroides dimidiatus by 
Gunther (1881: 243) from the Hawaiian Is- 
lands is open to question. It seems possible 
that he might have obtained L. phthirophagus 
and confused it with L. dimidiatus , for the 
latter, if it occurs in Hawaii at all, is certainly 
rare. On one occasion I observed a small 
individual of what I believe to be this species 
underwater in Kaneohe Bay, Oahu. 
Although generally seen around rock or 
coral, Labroides phthirophagus does not appear 
restricted to any special habitat. I have ob- 
served it in clear water of high coral cover 
such as Kealakekua Bay and turbid, at times 
brackish, water lacking living coral such as 
the Ala Wai Yacht Basin, Honolulu (it is, 
however, uncommon in the latter area). It 
occurs in water at least as shallow as 2 feet 
and has been seen at a depth as great as 90 
feet (it may occur deeper — there have been 
few observations beyond 90 feet). 
L. phthirophagus (Greek: phtheiros , louse; 
phagous , eat) is named for its habit of feeding 
on external parasites of fishes. 
The food habits of L. phthirophagus were 
suspected from observation of its picking at 
the surface of other fishes (Fig. 6) and from 
the knowledge that L. dimidiatus feeds on 
parasitic copepods and isopods from fishes. 
In order to obtain more positive evidence 
of such a mode of feeding, the contents of 
the alimentary tract of 11 specimens of L. 
phthirophagus in the collection of the Uni- 
versity of Hawaii were examined. None of the 
specimens represent type material. They were 
Fig. 6. Labroides phthirophagus picking at the body of 
a goatfish, Parupeneus multifasciatus. Reproduced from 
16 mm. movie film taken off Manana Island, Oahu. 
