ENEMIES OF TROUT 
25 
in the neighbourhood of its hiding place, than the larva slowly 
moves forth, glides beneath the body of its intended victim, and 
seldom fails to make a fatal stroke.” 
The great water-beetle {Dyiicus margtitalis) is a type of this 
group, and inhabits most of our waters. It is one of the largest 
British water-beetles, measuring an inch and a quarter in 
length, and is bulky in proportion. It is of a deep olive-green 
with a band of dull orange round the thorax and wing cases. 
On the head there is a V-shaped mark of a reddish colour, with 
two spots of like hue between the eyes. This Dyticus lives 
longer than most insects, and has been kept in captivity for 
three and a half years.* 
Another very common 
water-beetle, known as 
A alius sulcatus, is of suf- 
ficient size and power to 
prove a deadly assailant of 
any small fish. This and 
the Dyticus are often sold 
as specimens for the 
aquarium. 
Trout. 
• To the list of insect foes may be added the armies of dragon- 
flies, whose savage larvae are to be found in water almost every- 
where. The weapons of these larvae are if possible more 
formidable than those of water-beetles ; and their powers of 
locomotion are greater, for they dart rapidly from place to place 
by ejecting water from tanks within their bodies for this purpose, 
and are strong enough to attack not only the delicate and helpless 
new-born fry, but even fish much more advanced in power and 
size. 
Among fish, stickle-backs may be named as injurious to trout 
‘ Dyticus is usually spelt Dytiscus, -which is a mistake. 
