314 
ENTOMOLOGY. 
it is often associated, and whose name it most frequently bears. The 
aloes, however, produce their dowers laterally, that is, from the axils of 
the leaves; whereas those of the Agave are terminal, that is, placed on 
the point of the axis of the plant. There are several other plants consti¬ 
tuted in the same way. Some of the Palms are purely individual; 
but the most familiar example is the common house-leek, which though 
constitutionally like the agave, is neither ranged with it in the same 
natural order, nor yet in the same class of the sexual system. 
Entomologv.— The habits and transformations of the common gnat 
are truly wonderful. “ In the dipterous, or two-winged dies,” says a 
late writer, " the larva is termed a maggot, having no articulate, or pre¬ 
hensile feet; and generally preying on decayed animal substances. The 
house and desh-dy (musca domestica et earn aria) are well known fami¬ 
liar instances ; I shall, therefore, refer to the history of the gnat, as more 
particularly meriting attention. Its larva is an inhabitant of the water, 
and consequently needs some contrivance to breathe in the absence of 
those spiracles which are allotted to its land brethren. For this pur¬ 
pose a slender tube is attached to one of the posterior rings of the 
abdomen. The extremity of this tube is surrounded with a fringe of 
hairs, which when expanded, enables the larva to doat upon the surface 
of the water, and when it descends, the hairs shut round, enclosing 
a silver-like bead, which enables it to dive at pleasure.” This action of 
the larva may be seen in any open water-butt or cistern during the sum¬ 
mer months ; their jerking motions when disturbed readily point them 
out to the observer. “ When the larva assumes the pupa state, it loses 
this curious apparatus, and respires by two horns placed on the head ; 
and when at last perfectly formed as a gnat, again changes its breathing 
apparatus to respire through spiracles. In about ten days after the 
larva has become a pupa it prepares to emerge into the air;—but how 
is to accomplish this without wetting its wings, which if it once does it 
perishes. The process it performs with this intent is very curious. 
The moment the head of the pupa is raised above the water it bursts, 
from whence the perfect gnat within gradually puts forth its body, 
rising like the mast of a barge, after passing beneath a bridge. Thus 
the pupa-shell is now a boat, and the gnat the mast and sails; and it 
frequently happens that a gust of wind upsets the unfortunate and 
inexperienced navigator. But in general, when almost emerged he 
gradually lowers himself so as to touch the water with his feet (for this 
faculty of walking on the water is one of his powers), and then, stretch¬ 
ing his silken pinions, he flutters away to join the myriad bands of his 
companions, assembled for sexual intercourse, and which in dark squad- 
