DIPTERA. 51 



from the old skin through a longitudinal slit behind the head. At the fourth 

 moult emerges the pupa, which is a very different looking creature from the 

 larva, showing the cases for the antennae, wings, and legs of the adult, while from 

 the sides of its thorax project a pair of tubes, analogous to those of the larval tail, 

 and like these carrying the apertures of the tracheae. By means of its jointed 

 abdomen the pupa jerks itself about in the water in company with others of its 

 kind. At the appointed time a longitudinal split occurs on the back behind the 

 head, and, extricating itself from its pupal-case, the adult gnat appears on the 

 surface of the water, where under favourable conditions its skin hardens and its 

 wings unfold, while it floats upon the water using its discarded clothing as a raft. 

 If this time of danger be successfully overcome, the insect takes wing and joins its 

 companions in their mazy dance ; but, before acquiring strength to do so, it is at 

 the mercy of every wave or gust of wind, and if once swept back into the water, 

 its chances of survival are small. The above-mentioned banded gnat may be 

 distinguished from other British species by its large size, its spotted wings, and 

 striped legs and abdomen. The common gnat (G, pipiens), which is often abundant 

 in houses in the autumn, is much smaller and without the ornaments characteristic 

 of its larger ally. 



Travellers in the tropics are so familiar with mosquitoes that nothing we 

 can say can add to their knowledge of the subject. But to give those who 

 have been fortunate enough to avoid a practical acquaintance with them some 

 idea of the torments caused by these little pests, we quote the following passages 

 from the works of two well-known naturalists. Speaking of his sojourn at a 

 place on the Amazons, Bates says " at night it was quite impossible to sleep 

 for mosquitoes; they fell upon us by myriads, and without much piping came 

 straight at our faces as thick as rain-drops in a shower. The men crowded 

 into the cabins and then tried to expel the pests by the smoke from burnt 

 rags, but it was of little avail, although we were half suffocated by the operation." 

 Again, Emerson Tennent writes that "of all the insect pests that beset an 

 unseasoned European, the most provoking by far are the truculent mosquitoes. 

 Even in the midst of endurance of their onslaughts one cannot but be amused by 

 the ingenuity of their movements; as if aware of the risk incident to an open 

 assault a favourite mode of attack is, when concealed by a table, to assault the ankles 

 through the meshes of the stocking, or the knees which are ineffectually protected 

 by a fold of Russian duck. When you are reading, a mosquito will rarely settle 

 upon that portion of your hand which is within range of your eyes, but cunningly 

 stealing by the under side of the book, fastens on the wrist or little finger and 

 noiselessly inserts his proboscis there. I have tested the classical expedient 

 recorded by Herodotus, who states that the fishermen inhabiting the fens of Egypt 

 cover their beds with their nets, knowing that the mosquitoes, although they bite 

 through linen robes, will not venture through a net. But notwithstanding the 

 opinion of Spence, that nets with meshes an inch square will effectually exclude 

 them, I have been satisfied by painful experience that, if the theory is not altogether 

 fallacious, at least the modern mosquitoes of Ceylon are uninfluenced by the same 

 considerations which restrained those of the Nile under the successors of Cambyses." 

 An interesting question arises in connection with mosquitoes as to the nature of 



