968 Marvels of the Universe 
When undisturbed the larva usually hangs head downwards from the surface of the water, with 
only the tip of the tail-tube breaking the surface. In this position the openings of the two main 
air trunks of the body are exposed to the atmosphere and the larva is breathing ; at the same time 
it is also feeding, for the brush-like organs at the mouth maintain a constant stream of water which 
brings with it the organisms which form the food of the creature. On the approach of danger the 
larva closes five little flaps at the end of the breathing-tube, by this action losing the support of the 
surface-film, when it sinks by its own weight. As soon as the danger is past and the larva wishes 
to return to its former position, it has to swim violently upwards. This condition, it will be noticed, 
is just the reverse of that which obtains with the larvee of water-beetles ; these are lighter than the 
water, and in order to remain below have to hold on to submerged bodies ; when they want to come 
up to breathe they merely let go their hold and automatically rise tail first to the surface. 
When full-grown the larva moults and becomes a pupa. In addition to the rudiments of the 
limbs of the perfect Gnat being now visible, other great changes have taken place. The creature 
no longer breathes through its tail, but through two small tubes, or trumpets, that have now 
appeared behind the head. Consequently 
the pupa has to adopt a different posi- 
tion in the water, and floats back up- 
wards, with its tail curled underneath it 
and only the two breathing trumpets 
breaking the surface. In a few days the 
fly is ready to emerge; the pupa skin 
splits down the middle of the back and 
the body of the fly bulges out through 
the slit. Slowly and gradually it pushes 
itself further and further out ; legs and 
wings can be observed to be pulled out 
of their several sheaths, until the creature 
seems to be standing on its tail, with its 
extremities still caught in the floating 
pupal skin. It now rests for a few 
Photo bu) [H. S. Cheavin. F.RLMLS. : 5 I IIs O) be 1 e l I 
THE GNAT. moments, then pulls its legs clear; the 
The new-born Gnat is emerging frem the floating skin of the wings and body follow, and after a very 
chrysalis, maintaining its balance whilst withdrawing its body, wings short rest either on the floating skin or on 
and long legs. (Enlarged about ten times.) 5 Z : 
the surface of the water, it flies away. 
The whole process only occupies a few minutes from first to last, the wings being expanded as they 
leave their pupal envelopes. 
The Gnat is a beautiful object under the microscope, or even for observation with a good lens. 
The delicate scales with which the body and wings are somewhat sparsely clothed, the plumose 
antenne, especially those of the male, and the complex proboscis, consisting of a strong supporting 
sheath enclosing a whole armoury of exquisitely delicate lancets, are all objects whose beauty cannot 
fail to arouse our admiration, whatever may be the effect produced by the operations of the latter 
upon our persons. Asa matter of fact, the male Gnat is perfectly harmless ; it is the female alone 
that does all the mischief. 
Irritating though Gnats may be, we in this country should be thankful that Gnat-bites are 
nothing worse than Gnat-bites. In warmer climates there is always the possibility that they may 
mean infection with malaria, yellow fever, or other diseases due to a microscopic parasitic organ- 
ism living in the blood. The parasite is sucked up by the Mosquito from some person already 
infected with the disease, and in its body it undergoes a certain development until it in turn 
is communicated to some healthy person bitten later. Now we see how important it is that open 
