15 
Pour medium-sized male /unduli were placed in a jar containing 
larval shells and a few mosquito larve. he larvae were seized in- 
stantly, but not all of them had been captured before the voracious 
killifishes seized and partly devoured larval and pupal shells. The 
larval shells were spit out rather forcibly on being about half swallow: 
ed. ‘The spitting reaction was not limited to larval and pupal shells, 
however. In many of my experiments with killifish placed in jars 
with large numbers of mosquito larvae, a sated individual would act 
like the small boy at Thanksgsiving, and seize larvee which it could 
not stomach. After a few such “tries” the fish sometimes rest and 
meditate on the bottom of the aquarium, occasionally seizing a few 
other larvae and swallowing them. From our experiments there is 
little evidence of a selection of one particular species of mosquito 
larva. The selection of the mosquito larva in preference to water 
tigers, Notonecta, shrimps, spiders, daphnids and vegetable food, is 
attributable, I believe, to the stimulus of the extremely active mos- 
quito larva to the visual sense of the fish. The fish always selected 
motile larve in preference to dead or quiescent ones; they chose the 
larvee as they came to the surface to breathe or seized them as they 
were sinking. While it is true that the fish also ate dead larvee and 
those which were quietly resting at the bottom of the jar, they also 
seized other animals, bits of alga, in fact almost anything which 
appealed to the eye. The olfactory and gustatory senses came into 
play in the rejection of unsuitable or distasteful food. 
Smell, I maintain, is a secondary sense in the capture of mosquito 
larve by the killifish, Fundulus heteroclitus. 
CONCLUSIONS 
The greatest natural enemy of the salt-marsh mosquito is the 
barred killifish, Yundulus heteroclitus. It also eats many green-head 
flies. 
Fundulus heteroclitus captures larve, pupe and adults of the 
mosquito, eating as many as 50 a day and killing many more. 
The vast hordes of fishes which migrate to the shallows and even 
into almost fresh water render the species especially formidable. 
The number of enemies of the mosquito which are eaten by 
Fundulus heteroclitus is negligible and is more than compensated 
for by the great preponderance of mosquitoes in the diet of the fish. 
The ease with which Pundulus may be artificially fertilized and 
the remarkable vigor and resistance of the young embryos make the 
stocking of pools and streams with this species a simple matter. 
