Review of Labroides — Randall 
331 
Fig. 3- A pair of Labroides dimidiatus picking at the 
wrasse Epibulis insidiator. Reproduced from 16 mm. 
movie film taken in the lagoon of Takaroa, Tuamotus. 
and three small fish scales in the stomach and 
the digested remains of numerous calagoid 
copepods in the intestine. A 71 mm. speci- 
men from the Society Islands had two cala- 
goids in the stomach and four calagoids and 
one larval gnathiid isopod in the intestine. 
One section of the intestine had a bit of soft 
bottom debris including a few fragments of 
algae. A 65 mm. specimen from the Society 
Islands had an empty stomach and the re- 
mains of 13 calagoid copepods and 1 lernaeid 
copepod in the intestine. A 24 mm. juvenile 
had eaten five small larval gnathiid isopods 
and three immature calagoid copepods. Non- 
parasitic crustaceans were not found in any of 
the specimens examined. The bottom debris 
in the one specimen may indicate occasional 
feeding on free-living forms, however, the 
species appears to be at least dominantly a 
feeder on crustacean ectoparasites of fishes. 
Although Doty and Morrison {op. cit.) 
stated that parrot fish were feeding when the 
labrid cleansed them, host fishes are generally 
not so oblivious to having their parasites re- 
moved. Usually the fishes display some dis- 
tinctive behavior during the process. Often 
they remain completely motionless in the 
water, although they may swim slowly. Usu- 
ally their fins are fully erected (this may be 
associated with the high percentage of crusta- 
cean parasites which occur on the fins as 
compared with the rest of the body epider- 
mis), and there may be a disorientation of the 
body to a position out of the vertical plane 
(i.e., tilted to one side) or with the anterior 
part of the body elevated. At times color 
changes are apparent. The black-hued surgeon 
fish Acanthurus achilles Shaw, for example, 
may become bright blue when picked over 
by Labroides. 
Of all of the species of Labroides , L. dimidi- 
atus is the least wary and will often swim up 
to a human observer, sculling along by pec- 
toral fins alone in typical wrasse fashion, as if 
to investigate the possibility of human ecto- 
parasites. I have experienced a picking at the 
hairs of my legs by this species and on one 
occasion a persistent and vigorous nipping 
at a small mole on my chest. 
Randall {op. cit.) noted a peculair mode of 
swimming often displayed by L. dimidiatus 
when near other fishes, describing it as an 
oscillation of the posterior part of the body 
during slow progression. Doty and Morrison 
wrote that this species swam "in an odd 
leaping fashion, somewhat like a finch in 
flight." I presume that this "dancing” about 
other fishes by this and other species of 
Labroides , coupled with their remarkable col- 
or, serves to enhance their recognition by the 
other fishes. Further, I noted in the Society 
Islands that L. dimidiatus , when near other 
fishes, often elevates its dorsal fin, especially 
anteriorly, such that the black forward part of 
the fin appears like a conspicuous black 
triangle. 
On several occasions I have seen Labroides 
dimidiatus enter the buccal and gill cavities of 
larger fishes, ostensibly to remove parasites. 
Probably this occurs more often than these 
few observations suggest, for the proximity 
of a swimmer appears to frighten the host 
fishes sufficiently to preclude their entering 
