ON MICROSCOPIC DISCOVERY. 



609 



grains. The hairs are very seldom disposed 

 in so regular a manner as they are represented, 

 except when the insect floats with the body 

 in the water, and the tail with its hairs a little 

 lower than the surface, for they are then dis- 

 played exactly as delineated in the cut annexed. 

 The tail serves the larva both for the purposes 

 of swimming and breathing, and it receives 

 through the tail that which is the universal 

 principle of life and motion in animals. By 

 means of (he hairs it can stop itself at pleasure 

 when swimming, cr remain suspended quietly 

 in the water for any length of time. The mo- 

 tion of the insect in swimming is very beauti- 

 ful, especially when it advances with its whole 

 body floating on the surface of the water; after 

 filling itself with air by the tail. To set out, 

 it first bends the body to the right or left, and 

 then contracts in the form of the letter S, and 

 again stretches it out in a straight line : by 

 thus alternately contracting and extending the 

 body, it moves along on the surface of the 

 water. These larvae are generally to be found 

 in shallow standing waters, about the begin- 

 ninor of June." 



We are permitted by Mr Pritchard to copy 

 from the new edition of his Microscopic Illus- 

 trations (p. 70 et seq.) the following descrip- 

 tion and illustration of the larva of a British 

 llydrophilus (Hydrophilus caraboides^) 



" In examining the peculiarities of the 

 structure and habits of this larva, what most 

 strikingly attracts our attention is its ferocious 

 and savage disposition, and the fitness of its 

 organs for the exercise of its ravenous propen- 

 sities. It may be safely asserted that no spe- 

 cies of larvae is. known to be provided with 

 weapons of destruction so powerful, so numer- 



VOL. n. 



ous, and so well adapted to their end, as those 

 which this creature possesses. It is on this 

 account that it has been properly called the 

 Water Devil. Its size is but little inferior to 

 that of the larvae of any of <he British cole- 

 optera, as it measures, when arrived at ma- 

 turity, an inch and a half in length, while the 

 superior strength and courage manifested in 

 its attacks on small fish, and other animals 

 larger than itself, is truly surprising. 



" About the latter end of April, and during 

 the month of May, small nests of these insects 

 are often found floating among weeds and 

 water plants, in stagnant pools, and are fre- 

 quently taken in the nets of those who are 

 searching for the early kinds of larva. They 

 are in the form of balls, of a dusky white 

 colour, and a silky texture, and have each a 

 small stem of the same nature as th.e nest, but 

 more dense. By means of this filament they 

 are attached to the roots or stalks of weeds at 

 the bottom of the water. In tins situation 

 they remain during the winter, and are thus 

 effectually preserved from the effects of intense 

 cold. Early in the spring, the stem or cable 

 to which we have referred is detached from 

 the weeds, by the winds which at that time 

 prevail, and the nest rises to the surface of 

 the water, and there floating, receives the 

 genial influence of the sun. These nests may 

 be taken and placed in a basin of water, and, 

 as the season advances, hatched by the heat 

 of the sun. On the larva leaving the nest, 

 which it accomplishes by gnawing a hole in 

 the side, the infant immediately descends to 

 the bottom of the vessel, with its jaws extended 

 in search of prey, and eagerly devours all the 

 small aquatic insects that are within its reach ; 

 if however, there is a scarcity of food in the 

 immediate neighbourhood of the nest, they 

 may be seen to attack and devour each other." 



" These larvae, as well as most of those of 

 the larger kind, are found at a greater depth 

 of water than are the smaller ones ; although, 

 in their pursuit of small prey, they may oc- 

 casionally be taken in shallow places. In its 

 infant slate, this larva is very transparent ; 

 hence its internal structure may be clearly 

 distinguished. When about a quarter of an 

 inch in length, it swims very nimbly. The 

 colour of the head is a strong Indian yellow, 

 with darker shadings of a bright chestnut ; the 

 eyes are now bright carmine. It is more 

 sparingly covered with hairs, and its swim- 

 ming appendages are shorter than at a more 

 advanced period; and the head is larger, in 

 proportion to the size of the body, than when 

 the creature has arrived at maturity. In this 

 respect it resembles many other creatures in 

 its mode of growth, the head seeming to be 

 developed and perfected before the rest of the 

 system." 



4H 



