460 
PACIFIC SCIENCE, Vol. XXI, October 1967 
was an infection by a filamentous fungus-like 
organism which has occasionally struck experi- 
ments in the laboratory but which has not been 
identified. It is unfortunate that higher experi- 
mental temperatures were not available at the 
time. The 7-8 days required to reach the first 
moult at 25 °C is approximately the same 
amount of time as is required by some other 
tropical species of hermit crabs in the labora- 
tory, but is longer than for others. This period 
would almost certainly be shortened by sev- 
eral days at still higher temperatures. 
DESCRIPTION OF THE LARVAL STAGES 
There may be four or five zoeal instars in 
the development of T. magnifcus prior to the 
glaucothoe stage. 
General Features of the Zoeal Stages 
The rostrum is long, exceeding the cephalic 
appendages, rather broad and deep, with the 
tip slightly curved ventrad. Each of the anterio- 
ventral corners bears a small blunt spine pro- 
jecting anteriolaterally. The carapace bears no 
large spines posteriolaterally on the margins, 
but has numerous spinules which give the 
carapace a roughened appearance. These spi- 
nules extend onto the more posterior portions 
of the body as well, being especially noticeable 
on the dorsal surface of the abdominal somites 
and on the telson. As development proceeds, 
the spinules become relatively smaller until 
they are hardly noticeable in the last zoeal 
stage (Figs. 1 and 2). The telson is much 
broader than long in the first stage and in sub- 
sequent stages becomes progressively more 
elongate (Fig. 7). 
The appendages are generally symmetrical 
throughout larval development, with occasional 
differences of one or two setae between one 
side and the other, but a notable exception is 
the pair of mandibles which are quite asym- 
metrical throughout the zoeal stages. Because 
zoeal mandibles have seldom been described 
or illustrated in detail, the functional and pos- 
sible systematic significance of mandible arma- 
ture is not well understood. Therefore both 
mandibles of each stage of this species have 
been illustrated from two aspects. 
The zoeal stages have a yellow-orange overall 
color. Some of the parts of the exoskeleton, 
notably the tip of the rostrum and the ends of 
the antennules, are yellowish but not from 
chromatophores. The carapace has a very dif- 
fuse yellow-orange color, also apparently not 
due to chromatophores. There are orange-red 
chromatophores laterally under the anterior 
half of the carapace, and others deep in the 
body at the bases of the maxillipeds, and there 
is a very large orange chromatophore on each 
side of the fifth abdominal somite near the base 
of the lateral spines. There are two pairs of 
similar large orange chromatophores anteriorly 
on the telson. Red chromatophores are found 
at the base of the antennae, on the labrum, 
and perhaps on the bases of the mandibles. A 
pair of red ones occurs on the first abdominal 
somite. 
First Zoea 
CARAPACE length: 1.4-1. 6 mm 
TOTAL LENGTH: 2. 7-2. 9 mm (3 specimens) 
The first larval instar, as is typical of hermit 
crab larvae generally, has the eyes fused to the 
carapace. The sixth abdominal somite is fused 
to the telson, which bears the normal comple- 
ment of 7 -f- 7 marginal telson processes, the 
outermost of which is a heavy spine, the sec- 
ond a delicate hair, while the others are articu- 
lated plumose setae. 
The appendages of the first zoea (refer to 
figures) differ in no important respect from 
those of other species of hermit crabs at that 
stage (except that the well formed anterio- 
lateral spine on the antennal scale is not always 
present in other diogenid hermit larvae and 
the medio-proximal comer of the basipodite of 
the first maxilliped has only setae, not a hooked 
process as in some other species of Diogenidae) . 
Second Zoea 
CARAPACE LENGTH: 1.8-1. 9 mm 
total length: 3.5— 3.8 mm (4 specimens) 
The second larval instar differs from the 
first in many respects. The eyes are now free of 
the carapace and are stalked. The telson, while 
still fused to the sixth abdominal somite, has 
added a median pair of telson processes. All 
of the appendages have changed as shown in 
the figures. 
The antennule has added some terminal aes- 
thetascs, for a normal total of 6 or 7 terminal 
