Terrestrial Amphipoda — Hurley 
125 
sodated loss of sensory perception; the body 
in ni.any species has become capable of rolling 
into a balb or ” conglobating/' thus giving 
the animal greater protection from desiccation 
and, presumably, from its natural enemies; 
and locomotory powers have been reduced by 
weakening of the peraeopods (Van Name, 
1936:282,328). In the terrestrial Amphipoda, 
the antennae are much simpler than in most 
marine and littoral species; they are more 
slender; they lack calceoli and other similar 
sensory structures; but there does seem to be 
a development of fine setae of a tactile nature. 
Terrestrial species are extremely mobile. There 
is no morphological adaptation to protect the 
gills— if anything they are more exposed by 
reason of their greater length; nor is there 
any sign of structural adaptation like the 
"conglobating" power of isopods. However, 
with increase in gill size, as in Talitrus 
sylvatkus, it would not have been unreason- 
able to have expected some physiological or 
morphological modification analogous to the 
development of pseudotracheae in the ter- 
restrial isopods. It is probably because of the 
lack of just such modifications that the ter- 
restrial amphipods, seemingly well suited for 
the leafmould environment, have not oc- 
cupied other, more stringent niches. 
What has been said of the terrestrial iso- 
pods, also may be said of the amphipods: 
"Any success which the group enjoys on 
land is due, not so much to the development 
of characters conferring independence of the 
environment, but to behavioural mechanisms 
which keep them for the most part in moist, 
cool places. . . . The general picture which 
emerges is of a group of animals compara- 
tively ill equipped for life on land. All the 
devices which permit such existence are in 
some degree makeshift. . . . And yet, despite 
these disadvantages, the animals are by no 
means uncommon, and there is little doubt 
that the success which they do enjoy is the 
result not so much of morphological or physi- 
ological adaptations as of behavioural mecha- 
anisms which restrict them to the cryptozoic 
niche where the rigours of true terrestrial 
existence, as well as its opportunities, are 
avoided” (Edney, 1954). 
SUMMARY 
The term "supralittoral” is applied to 
Amphipoda of the seashore zone; "terres- 
trial” is restricted to those species which are 
entirely independent of sea water. Almost all 
of these are leafmould species which are 
characteristic of, and restricted to, the Indo- 
Pacific islands and land masses. The terrestrial 
amphipods have colonised the land directly 
from the littoral zone. The forest floor pro- 
vides the relatively stable conditions which 
assist colonisation and provide considerable 
protection in unfavourable times. Drastic 
changes in feeding habits have not been 
necessary. 
Adaptations which have taken place or 
seem most likely to have occurred are these: 
1 . Feebly chelate gnathopods in Talitrus 
and reduced male second gnathopods in 
Orchestia species are correlated with changes 
in sexual habits, the development of large 
second gnathopods in the male to hold the 
female during copulation having been lost. 
In Talitrus saltator stout antennae are used for 
this purpose, but in most terrestrial amphi- 
pods the antennae are long and slender, and 
there must have been a further, as yet unde- 
scribed, change in sexual habits. Scabrous 
pellucid areas on the male gnathopods, char- 
acteristic of terrestrial amphipods, are prob- 
ably of tactile sensory nature and possibly 
correlated with feeding habits. 
2. There is a tendency for the male second 
gnathopod in mature animals of some species 
to resemble the immature males in other, less 
terrestrial, species. It is suggested that species 
formation in terrestrial amphipods is corre- 
lated with neotony. 
3. There is evidence that males are com- 
paratively few in some terrestrial populations, 
although this may be true only of certain 
species and times of the year. 
4. Fewer but larger eggs are produced by 
