246 



BULLETIN THE BUREAU OI^ FISHERIES. 



caudal gills are small and scattering. The ground color is white, covered with a complicated pattern of 

 light russet brown; last four abdominal segments, legs, and caudal gills nearly all brown, with narrow 

 stripes of white; respiratory tracheae bright golden yellow. 



The Mask. — Mentum one-half wider than long, with slightly convex sides; distal margin nearly 

 three times the proximal; no lateral setae, one marginal seta near the distal end, one mental seta; distal 

 margin smooth. Lateral lobe three-fourths longer than wide; no setae on the outer margin; raptorial 

 seta just reaching the tip of the movable hook, the latter long and stout; a minute accessory spine out- 

 side the base of each raptorial seta; distal margin deeply toothed, inner tooth cultriform. 



Figs. 61 to 63. — Development of Enallagma signatum: 61, egg: 62, mask of newly hatched nymph: 63, newly hatched nymph. 



GENERAL CONCLUSIONS. 



1. Odonate nymphs feed upon small moUusks, insect larvae (including smaller 

 nymphs), pupae and adult?, entomostraca and larger Crustacea, and algae. Some of 

 their food, such as Chironomid larvae, mayfly larvae, entomostraca, etc., is the same 

 as that of young fish, but they also eat the larvae or adults of many animals that are 

 directly harmful to small fishes, such as diving beetles, water boatmen, crayfish, and 

 Cypris. 



2. A few of the largest species may sometimes eat a small fish under natural con- 

 ditions, but this is apparently due to stress of hunger and the lack of other food. War- 

 ren has proved (p. 206) once for all that the diet of a nymph in captivity furnishes no 

 criterion whatever as to its natural food. Careful obser^^ations under natural condi- 

 tions show that even an Anax nymph need not be regarded as a menace to fish culture, 

 but that it may become actually beneficial. 



3. Odonate nymphs furnish one of the very best foods for fishes; the small species 

 and the young of the larger species are freely eaten by the fingerlings of practically all 



