CORDULEGASTER 157 
of the stream and the nymphs wander aimlessly over the bed. Because the 
nymphs are free on the stream bottom each freshet during the three or four 
years of nymphal life serves to wash them farther downstream so that when they 
come to emerge they may be far downstream from the place where the eggs were 
deposited. 
I have never observed copulation in this species, but in the matter of ovi- 
position I was more fortunate. August 16, on Stevens Creek, I saw a female 
oviposit. She flew hurriedly up the creek and every few yards stopped and with 
a sudden backing or downward stroke, while hovering with the body in a per- 
pendicular position, stabbed her large ovipositor into the coarse sand along the 
stream edge, where the water was about an inch deep. She thus thrust her 
abdomen down through the inch of water driving her ovipositor into the sand 
beneath. Four to ten such perpendicular thrusts were made at each stop. Some 
stops were along the open beaches, but more were in quiet nooks between large 
rocks where she would have barely room enough for her wing expanse. She 
usually faced the center of the stream while ovipositing, though once she faced 
upstream and once she faced the bank. The peculiar perpendicular position 
with the up and down motion reminded me strongly of the manner of oviposition 
of some crane flies, except that the latter oviposit in damp soil and support 
themselves on their slender legs while making the vertical thrusts. Fig. 11 shows 
the position of the female while ovipositing. 
The nymphs are shortlegged, slow moving creatures and are usually abundant 
in the streams of the Coast Mountains. They occur with Octogomphus nymphs 
in the leafy trash of the eddies, but are also found crawling slowly about over the 
bed of the stream. Their very slow and apparently cautious movements do not 
betray them, and they carry with them further protection in the coat of long 
hairs which collects dirt and on which flourishes a thick growth of filamentous 
algae. Because of this covering of dirt and algae the nymph, though on an 
otherwise barren bottom, will usually escape the closest scrutiny of the collector, 
for it does not appear any different from a stick or a stone covered with dirt 
and aquatic growths. On Mission Creek, Santa Barbara, California, I found 
nymphs of dorsalis buried in flocculent silt, as described for the various eastern 
species of the genus. 
At emergence, which takes place in June, the nymphs crawl from 1 to 5 feet 
up the trunk of the nearest alder tree. This species spends 4 years in the egg 
and nymphal stage. 
The senior author kept nymphs of this species alive in a dish of 
water and sand for some weeks on his desk in California in order to 
observe their feeding habits. A half grown nymph, thrown out of the 
sand, chanced to wander in front of a grown nymph and was seized by 
the cannibal and wholly devoured in half an hour. Damselflies (mostly 
Enallagmas) were used for regular feeding. Several were eaten daily by 
each nymph. 
A large Enallagma nymph seized by its abdomen clung with its feet 
to the back of the head of the biddy nymph and would not let go until 
the latter compelled it by repeated forward thrusts of its tail spines 
