86 UNIVERSITY OF COLORADO STUDIES 



fish, as given by the several writers who have studied it, consists of almost any- 

 thing which comes the way of the fish. It has a voracious appetite and feeds to 

 a considerable extent on small fishes. 



Cristivomer namaycush was introduced into Twin Lakes about twenty years 

 ago with success, some very large specimens having been taken from those lakes 

 in the past few years. Juday' states that a number of individuals weighing from 

 15 to 20 pounds were caught during the summer of 1903, the fishermen using large 

 hooks baited with pieces of suckers. Mr. Irwin Simonson secured for the writer 

 the weight and measurements of a large specimen of this species caught in Twin 

 Lakes on June i, 1907, by Mr. W. W. Fay of Buena Vista. This fish weighed 

 20j pounds and was 39I inches in length ; the head measured 85 inches in length, 

 greatest circumference 2 if inches, tail when spread io§ inches. A live minnow 

 was used for bait. The Mackinaw Trout has been reported by several fishermen 

 as the most abundant large fish now in Twin Lakes and it has been suggested that 

 the increase of this fish is correlated with the decrease of the Yellow-finned Trout. 



Order Haplomi 



The Pike-like Fishes, including the Mud Minnows, the Pickerel, the 

 KiUifishes and the Cave Blindfishes 



Family POECILIIDAE 



The Killifishes and Top-minnows 



Body somewhat elongate, more or less terete in the anterior half, distinctly 

 compressed posteriorly; top of the head usually flattened; mouth terminal and 

 broad, lower jaw projectmg in many species; scales large, cycloid; lateral line 

 wanting or represented by but a few pores; sexual dimorphism pronounced in most 

 species, many being ovo viviparous; size small; colors of tropical species brilliant 

 and varied. 



The Poeciliidae are small fishes of the fresh waters of Europe, Asia, Africa 

 and the Americas. A few species are marine and many are quite abundant in 

 the brackish water of salt-marshes. Because of their small size and ability to live 

 in warm and rather impure water they are often very numerous in small streams 

 and ditches. One species, Acanthophacelus reticulatus (Peters) and several closely 

 related forms, known collectively as "Barbadoes Millions," have become of con- 

 siderable economic importance recently as destroyers of mosquitos in the West 

 Indies and South America. These little fishes are able to live in the shallow 

 trenches of the sugar plantations and even the ditches in the streets of the small 

 towns, feeding upon the mosquito larvae. The "Millions" have proven very 

 effective enemies of the young mosquitos, contributing in this way to the control 



'/. U . Fish Com., Vol. XXVI p. 162, 1906. 



