110 
PACIFIC SCIENCE, Vol. XIII, April, 1959 
recorded as many as 4000 amphipods per 
square meter. They are a very conspicuous 
part of the fauna, both because of their num- 
bers and also because of their habit of jump- 
ing when the litter is disturbed. They eat 
fallen leaves, and there is little doubt that 
they play a major part in the disintegration of 
leaf litter in Australian rain forests” (Birch 
and Clark, 1953). 
The observations which follow represent 
an attempt to piece together information 
acquired incidentally in systematic studies. 
They are almost entirely unsupported by ex- 
perimental evidence, but are tentatively put 
forward to draw attention to the problems 
involved and to opportunities for future 
research. 
ACKNOWLEDGMENTS 
I wish to thank Professor L. R. Richardson 
of the Zoology Department, Victoria Uni- 
versity College, Wellington, New Zealand, 
under whose supervision this work was origi- 
nally carried out, for his advice and assistance; 
and also Dr. B. M. Bary and Mr. W. H. 
Dawbin, who have most generously read the 
manuscript and offered valuable criticism 
and encouragement. 
DEFINITION 
It is necessary to draw attention to past 
misuse of the term "terrestrial” in speaking 
of amphipods. 
In each of the three talitrid genera, Talitrus, 
Talorchestia, and Orchestia, there are species of 
"sandhoppers,” amphipods which live in the 
beach zone above low-tide level and often 
reach some distance above high-tide mark. 
These are quite distinct from the terrestrial 
Amphipoda which inhabit the forest floor of 
the Indo-Pacific region. In the European 
zone, where terrestrial species are not indige- 
nous, there has been a tendency to speak of 
the littoral species as being "terrestrial”; for 
instance, Dahl (1946) speaks of Talitrus salta- 
tor as a terrestrial species, one "whose most 
important functions— eating, breeding, etc. 
are performed on land.” He remarks further 
that "their main distribution is passive and 
takes place in sea water.” This conclusion 
points up one of the differences between the 
truly terrestrial species and those of which 
Dahl is speaking. The ecology of the terrestrial 
species is not sufficiently well known to assert 
in definition that their distribution is active, 
but it is clear that it does not take place in sea 
water. Those species of which Dahl speaks 
should be referred to, I propose, as "supralit- 
toral” (cf., T. A. and Anne Stephenson, 1949). 
Those species which are essentially independ- 
ent of sea water, that is, which may occur in 
leafmould at the water’s edge but may equally 
as well occur in leafmould thousands of feet 
above sea level and miles away from the sea- 
shore, may then properly be referred to as 
"terrestrial.” 
The term "cryptozoic” is also used in this 
paper. It was first proposed by Dendy (1895) 
for "the assemblage of small terrestrial ani- 
mals found dwelling in darkness beneath 
stones, rotten logs, and the bark of trees, and 
in other similar situations.” Interestingly 
enough, Dendy specifically includes the am- 
phipods, Orchestia sylvkola, from New Zea- 
land, and Talitrus sylvaticus from Australia, in 
this fauna. 
As an alternative, I have occasionally used 
the more colloquial term "leafmould species” 
which is both apt and accurate in describing 
the niche which these animals fill. It avoids 
confusion with the supralittoral species, but 
is of less universal application. 
DISTRIBUTION 
The most striking feature of the distribu- 
tion of terrestrial Amphipoda is that they are 
domiciled essentially in the Indo-Pacific re- 
gion, and especially in the Southern Hemi- 
sphere. Stephenson (1935) no doubt had this 
localisation in mind when he compiled his 
paper on "The Indo-Pacific Terrestrial Tali- 
tridae,” but he did not elaborate any thesis 
beyond observing that the terrestrial species 
were characteristic of the Indo-Pacific Ocean, 
