AQUATIC INSECTS 
Insects and their larve are one of the most unfailing sources of food 
supply for freshwater fishes. [here are many, however, which in some 
or all the stages of existence are injurious to the spawn and young, and 
these belong to many orders, families, genera and species, among 
them being some genera of the Heteroptera or Water-bugs; the Neurop- 
tera or Dragon-flies and kindred insects; the Diptera or true Flies; the 
Coleoptera or Beetles; the Lepidoptera or Moths; the Hymenoptera or 
Ichneumons; the Arachnide or Spiders; and other families of the insect 
world, or forms closely related thereto. 
Some are not entirely rapacious nor depend solely on the blood of 
animals for food, but also suck the juices from insects and plants, yet be- 
come active enemies in the confines of the rearing basins for fishes, in the 
absence of larger fishes which would devour them and their larve; thus 
permitting them to prey upon the smaller fishes and to soincrease in numbers 
as to become very destructive. These will be briefly described, their 
habits noted, and illustrations given for their identification. Others which 
serve as food for young and mature fishes will also be mentioned. 
Freshwater plants grow in more or less shallow water, as they are 
dependent for nutrition upon the decomposition of carbonic acid gas by 
sunlight, and as plant-feeding animals establish 
themselvesamong them, they are also frequented 
by predatory animals, to whom these serve as 
food. Insects are of both these classes but the 
predatory more particularly claim our attention. 
It should be stated that insects deriving oxygen 
from the air are generally lighter than water, 
so that, should they exhaust the air carried with 
them under the water or become disabled, they 

rise to the surface by gravity in such position 
FIG. 195. Outline of a Water Beetle. that the air-breathing parts first come to the 
. Ant : - . ae 
: Maxillary ‘Alpi. surface. The insects deriving oxygen from the 
: Ee fe air held in suspension in the water are heavier 
. Fore-leg. : c 
e. Thorax. than water and no effort is necessary for them 
f. Middle-leg. 2 : 
g. Elytron. to keep below the surface. Changes in water 
h. Suture. . = 
itranuies temperature are also provided against and most 
Levan. of the aquatic insects pass the winter in the 
k. Tarsus or foot. 
|. Tibia or shank. larval stage, to undergo the further transforma- 
. Femur or thigh. 
Eas: 
First three joints of foot, tions in the following spring or early summer, 
2G t 
