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For a long time we had in our collec- 
tion a single specimen of Rivulus flabel- 
licauda; a female. She lived in a large 
community aquarium in which sundry 
Barbus, Danio and other docile species 
mingled happily. The soon 
learned to associate the sound of a knife 
striking a board with an impending threat 
family 
—chopped earthworm—and in a moment 
would change from a calm, deliberative 
body to a turbulent mob, dashing and 
plunging about in their eagerness for the 
coveted morsel. The female flabellicauda 
was the only exception. She hovered 
unsociably in the background, making an 
occasional furtive venture into the food- 
eager crowd, but quickly darting back to 
cover. It was not until a male was placed 
in this tank that she lost her shyness. 
It is surprising how quickly a fish will 
discover, among scores of other species, 
one of its own kind. Barely a few mom- 
ents elapsed after the introduction of the 
male before both were swimming ex- 
citedly together near the surface. Reach- 
ing a floating plant, the male suddenly 
closed in sidewise upon the female, wave- 
like motion followed by a curling of the 
posterior ends of their bodies terminated 
in a violent effort, and the eggs were ex- 
pelled and fertilized. After an interval 
of rest the operation was repeated. 
That evening I secured a number of 
the eggs, which were attached to the 
plants, but they failed to hatch. This I 
think was due to the condition of the 
male, which had just finished a long 
journey. Later, however, we hatched 
and reared quite a number, for the spe- 
cies is very prolific. When discovered 
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| Rivulus Flabellicauda : 
| ERNEST LEITHOLE 
oom el, 
the eggs should be removed to a separate 
vessel. Hatching will take place in about 
two weeks, varying with the temperature, 
which should range from a minimum of 
70 degrees to 90 degrees. At the present 
writing we still have offspring of that 
first pair. 
This Rivulus comes from Central 
America and is a decidedly colorful fish. 
The back of the male is light brownish 
Rivulus flabellicauda 
(Syn. R. tenuis) 
gray merging into pale blue on the sides, 
marked with reddish spots; belly, citron 
yellow. The complimentary colors, blue 
and yellow, produce a fine effect, partic- 
ularly when intensified during the breed- 
ing season. Throat, pale orange to a rich 
red; gills dark blue green, with reddish 
dots; dorsal, yellowish, edged with light 
green; ventrals and anal, yellowish 
green; pectorals, greenish ; lower edge of 
caudal, pale orange, center light, light 
ochre to orange or red; top, greenish. 
The female is much plainer. Body, 
light brownish gray; gills, dark blue 
green; pectorals, yellowish; dorsal and 
ventrals, colorless; base of anal, grayish 
white blending into a light grayish brown 
