340 
PACIFIC SCIENCE, Vol. XII, October, 1958 
collected with rotenone from the islands of 
Oahu, Molokai, Maui, and Hawaii. The re- 
sults of the examination of the gut contents 
of these specimens are given below in Table 1, 
along with the date of collection and the 
standard length and sex of the specimens. 
It seems evident from Table 1 that L. 
phthirophagus feeds primarily on parasitic 
copepods and isopods from fishes. The fish 
scales and fragment of 'fin membrane were 
probably accidentally ingested in the process 
of picking at parasites. The cyclopoid cope- 
pods (lichomolgids and harpacticoids) do not 
appear parasitic. They are tiny, and when 
present in the gut, they are usually numerous, 
suggesting that they may have been encoun- 
tered by the labrid in a convenient concentra- 
tion. That parasites are not the sole diet was 
further shown by the following observation 
in Kealakekua Bay, Hawaii. Several nests of 
the pomacentrid fish Abudefduf abdominalis 
(Quoy and Gaimard) were seen at a depth of 
90 feet. When the guarding adult was fright- 
ened from one of the nests, a number of 
other fishes commenced to feed avidly on the 
eggs, among them an adult L. phthirophagus . 
Like Labroides dimidiatus and L. bicolor , L. 
phthirophagus is nonspecific in the fishes which 
it "services/’ Among the groups of reef fishes 
commonly seen participating in symbiotic re- 
lationship with L. phthirophagus are acanthu- 
rids, pomacentrids, scarids, labrids, chaeto- 
dontids, mullids, and plectognaths. 
Species of Caranx are not abundant in the 
Hawaiian Islands and none were observed in 
association with L. phthirophagus. Only one 
carangid, Decapterus pinnulatus (Eydoux and 
Souleyet), was seen to associate with the 
labrid. As a school of this species swam over 
the bottom off Waikiki, Oahu, a single 
Labroides phthirophagus swam upward to the 
school. One of the carangids left the school, 
swam slowly in a small circle, and quivered 
slightly as the Labroides pecked at its body 
surface. 
On one occasion when a Labroides was 
tending a large butterfly fish of the species 
Chaetodon lunula (Lacepede), the latter ceased 
its gill movements and elevated its operculum. 
The labrid inserted the anterior half of its 
body into the gill cavity through the gill 
opening, where, for several seconds, it pre- 
sumably searched for parasites. 3 The same be- 
havior was observed for the goatfish Paru- 
peneus prophyreus (Jenkins). With the use of 
self-contained breathing apparatus in clear 
water of about 40 feet in depth off Manana 
Island (Rabbit Island), Oahu, an individual 
Labroides phthirophagus was seen to enter the 
buccal cavity of an adult goatfish, Mulloi- 
dichthys samoensis (Giinther), by way of the 
mouth, such that the majority of the body of 
the labrid was lost from view. About five sec- 
onds elapsed before the Labroides emerged. 
Frequently the act of removal of parasites 
by Labroides phthirophagus occurs beneath a 
ledge or in an interstice in the reef, making 
observation difficult. Furthermore, the ap- 
proach of a swimmer usually interrupts the 
proceedings. For these reasons an effort was 
made to bring living specimens of Labroides 
into large aquaria where it was hoped detailed 
observations of behavior could be made. 
A total of three were caught underwater 
with dip nets in Kaneohe Bay and brought to 
the Honolulu Aquarium. None were main- 
tained in the aquaria long enough for normal 
feeding behavior to manifest itself; however 
the reactions of the resident fishes of the 
aquaria bear mentioning. When placed in a 
tank containing many moorish idols ( Zanclus 
cornutus (Linnaeus)), one balistid ( Khinecan - 
thus aculeatus (Linnaeus)), and an unidentified 
large scorpaenid, the Labroides swam about 
the aquarium, paying little attention to the 
other fishes. It was evident, however, that the 
3 1 suspect that the parasites removed from the gill 
cavity by Labroides are still principally calagoid cope- 
pods. In a study of the parasites of the surgeon fish 
Acanthurus triostegus sandvicensis Streets (MS data), I 
observed individuals of the most common parasitic 
copepod of this fish, an undescribed species of Lepeo- 
phtheirus , freely enter and leave the gill and buccal 
cavities of the fish. The genus Lepeophtheirus is the most 
abundant of the calagoids listed in Table 1. 
