72 



Fig. 38 represents this species very correctly ; it is black with a 

 broad margin of pale yellow on each side, and stripes of the same 

 colour across the front of the head and on both the front and hind 

 margins of the thorax ; there is also an irregular yellow line cross- 

 ing the wing covers near the tip. The under side is somewhat paler 

 with reddish markings. Examples of this insect are often brought 

 to us during the summer by persons who have found them in tubs 

 or barrels of water and who were puzzled to know how they could 

 get there. Beneath their hard wing covers they have a large pair 

 J-, of membranous wings, by the use of which they can fly with great 

 I ease ; by this means they are enabled to travel from pond to pond 



in search of their pi'ey. When wishing 



to change 



their location 



they crawl out of the water (usually towards evening) either up 

 some reed or other water plant, or to the margin of the pond, and 

 suddenly open their wing covers, expand their wings and rise into 

 the air almost perpendicularly to a great height. Their descent is 

 nearly as sudden and direct, and they often, when descending, drop 

 into the water with considerable force. It would appear that they 

 are enabled to distinguish the water from a considerable height by 

 its glassy surface, for sometimes they have been known to drop with violence upon 

 glazed garden sash, which they had evidently mistaken for water. 



The female lays her eggs in the water, where they soon hatch into young larvae, pos- 

 sessing the ferocious disposition and voracious appetite of their parents. The larvae grow 

 rapidly, and when mature are about two inches long, with large flattened heads armed 

 with sickle-like jaws, with which they seize other insects and hold them while they suck 

 their juices ; they sometimes quickly snip oflT the tails of young tadpoles, and are known 

 to attack young fishes and suck their blood. Many years ago, when searching with a 

 dip-net in a pond for the larvae of Dragon-flies, we caught one of these savage creatures, 

 and supposing it could be as safely handled as the libellulae larvae, took hold of it, when it 

 quickly turned and buried its sharp jaws in the flesh of one of our fingers, making the 

 blood flow quite freely. These larvae breathe through their tails, which they protrude 

 into the air for that purpose, When full grown and about to assume the pupa state, the 

 larva leaves the water, and burying itself in the earth, constructs there a round cell with- 

 in which it undergoes its change, and if this occurs in summer, it appears in two or three 

 weeks as a perfect beetle ; but if in autumn it remains in the chrysalis state all winter, 

 transforming to a beetle in the spring. 



Fig. 39 represents another of our large water beetles, Hydrojihilus 

 triangularis. This species is entirely black, and so strong and muscu- 

 lar as to be difficult to hold in the hand when captured. The relation- 

 ship of this tribe of insects (Ilydrophilus) with the preceding one 

 (Dytiscus) is very close. There is much similarity of form and a close 

 resemblance in habits ; their method of swimming, however, is differ- 

 ent, for while in Dytiscus both paddles are moved simultaneously, in 

 Hydrophilus they are moved alternately, hence the stroke of the latter is 

 much less effective. We are not aware that anything has been written 

 on the early stages of Hydrophilus triangularis, but in Europe the 

 life history of a closely allied species, Hydrophilus picetcs, has been 

 carefully traced by several observers, and there is little doubt but that 

 our species has similar, if not identical habits. The female of H. 

 piceus has the singular habit of spinning a silky cocoon for her eggs, 

 one side of which is furnished with an upright, bent, horny point, an 

 inch long, which is supposed to be serviceable in conveying air to the 

 eggs, some fifty or sixty in number, are placed in an upright position and in regular order 

 in theii- receptacle, which is round and flattened and attached to some water plant at the 

 surface of the water. In warm weather the larvae are hatched in from twelve to fifteen 

 days, when they escape at the lower part of the cocoon, which is closed only by a few 

 threads. They undergo three moultings, and when full grown measure nearly three inches 



Fig. 39. 

 interior. 



These 



