Field Identification of Five Species of Californian 
Beach Hoppers (Crustacea: Amphipoda) 
Darl E. Bowers 1 
While studying the correlations between the 
distribution of five species of beach hoppers of 
the genus Orchestoidea and the physical and 
biotic factors of their sandy beach habitat, it 
became necessary to identify with certainty the 
animals collected from the many beaches sam- 
pled up and down the Californian coast. Since 
it was desirable tentatively to name the hoppers 
captured in the field, I made an effort to find 
characters which were easily observed on the 
beach and would allow such identification. As 
a result of my examination of many thousands 
of animals from over a hundred collecting locali- 
ties, I evolved a recognition of the five species 
mainly on the basis of pigmentation patterns, 
elements of which are relatively consistent in 
spite of the many variations to be found in the 
total pigmentation. 
The species under consideration are the two 
large hoppers, Orchestoidea calif orniana 
(Brandt) 1851, and O. corniculata Stout 1913; 
the two somewhat smaller species 0. columbiana 
Bousfield 1958, and O. pugettensis (Dana) 
1853; and the small species, O. benedicti Shoe- 
maker 1930. 
Laboratory identification of these has been 
made possible by E. L. Bousfield ( 1957, and 
particularly 1959), to whom I am indebted for 
his help with some of the key characters. In 
these papers Bousfield has described a new spe- 
cies from southern California, 0. minor, similar 
to O. columbiana, but with a few subtle anatom- 
ical differences. These will require statistical 
analysis in order to show more clearly the affini- 
ties of the two species. This newly described 
form will not be considered here since I have 
been mainly concerned with the beaches of 
central and northern California. 
The pigmentation patterns may be relied on 
for identification of both sexes for almost all 
1 Mills College, Oakland, California. Manuscript re- 
ceived January 30, 1962. 
sizes of animals, with the following cautions: 
( 1 ) The largest individuals of calif orniana al- 
most invariably have lost the dorsal pigmenta- 
tion, but color and form of the second antennae, 
as described below, will usually make this no 
problem; (2) the largest individuals of cornicu- 
lata may have lost the dorsal pigmentation, but 
again, color and form of the antennae will 
usually suffice; (3) the smallest individuals of 
all species (under 4 mm in body length) may 
be so lightly pigmented as to make identification 
difficult or to require magnification and lighting 
available only in the laboratory; (4) animals 
living on white or very light-colored sands 
usually are only faintly marked, in which case 
combinations of other characters may have to 
be used. 
Some general beach characteristics and hop- 
per habits may also be of use in identification 
but are not dependable alone. O. calif orniana 
is typically found on long exposed beaches 
composed of fine sand, with few if any rocks 
present, beaches that are wide from the fore- 
shore to back shore with dunes into which the 
hoppers may retreat during high spring tides 
and for breeding, beaches which usually have a 
quite flat foreshore, which is correlated both 
with exposure to wave action and with fine 
sand particles. O. corniculata, on the other hand, 
is typically found on shorter, more protected 
beaches composed of coarser sand, possibly with 
rocks or boulders present, beaches which may 
be narrow from foreshore to back shore with 
cliffs or piles of boulders preventing retreat dur- 
ing high spring tides (breeding animals are 
commonly found mixed with the rest of the 
population), beaches which may have a fairly 
steep foreshore, which is correlated both with 
protection from wave action and with coarser 
sand particles. These two animals are not often 
found together, but occasionally on a calif or- 
niana-dommated beach, as at Carmel, California, 
315 
