30 



and in this state doing great benefit in clearing swamps of miasma. It rises to the 

 surface for air, which it inhales through a single respiratory lube, situated near the tail. 

 They are consequently obliged to hold their heads down. In the vicinity of the respira- 

 tory tube is an orifice which forms the exterior termination of the digestive tube. 



When the larva is about to transform into the pupa or chrysalis state it contracts 

 and enlarges anteriorly near the middle, the larval skin is tlirown off, and the insect appears 

 in quite a different form ; the head and thorax are massed together, and the rudiments of 

 the mouth parts, wings and legs are folded on the breast. In a few days the pupa skin is 

 cast, the insect avaihng itselt of its old habiliments as a raft upon which to float, while its 

 body is drying, grows lighter, and its wings expand for its marriage flight. The males 

 are beautiful, both physically and morally, as they do not bite : their manners are more 

 retiring than those of their stronger-minded partners, as they rarely enter our dwellings, 

 but live unnoticed in the woods. A mosquito lives three or four weeks in the water before 

 changing to the adult or winged state ; how long afterwards they live we do not know. 



The House Fly {Musca Domestica). 



This insect is so well known to all our readers that it needs no more introduction 

 than the mention of its name. It is very widely distributed, being found in almost^ every 

 part of the world. Indeed I believe we are correct in saying that wherever man takes up his 

 residence, it is shared to a greater or less extent by Musca domestica. Thus, being a crea- 

 ture so familiar to us all, the knowledge of its history, habits and structure should possess 

 great interest. How often is the question asked, in the spring or early summer time, 

 " Where do all these flies come from ?" and how seldom is an intelligent answer given. 

 About that time of the year several smaller species of flies are very abundant, and it is 

 commonly supposed that these small flies grow into the larger ones, people generally know- 

 ing little or nothing of the well established fact that winged insects never grow ; their 

 growth is completed in the earlier or larval stages of their existence, and when once they 

 have arrived at perfection, they cease to grow, and the end and aim of their existence 

 appears to be the propagation of the species. 



As we are so familiar with Musca domestica in its perfect or winged state, we will fol- 

 low its history from this point. In this insect the sexes are perfectly distinct, the female 

 being recognisable by the presence of a little tube or ovipositor situated at the end of the 

 abdomen. This organ is formed of three or four rings which the fly can extend or re- 

 tract after the manner of a telescope, and which it employs for the purpose of depositing 

 her eggs. Internally the organs of the female consist of a pair of branching tubes in 

 which the ova are developed. The male is furnished with tubes and glands necessary for 

 the development of the fructifying element. 



A celebrated German naturalist, Keller, who studied attentively ths history of the 

 house fly, tells us that the female deposits her eggs six or eight days after impregnation. 



his she usually does in such decaying substances as her instinct shows her to be suitable 

 for the nourishment of her larvae, as for example in the heaps of decaying vegetables 

 found near our dwellings. If the fly be enabled to choose the place which suits her best 

 for the deposition of her eggs (as for instance in a sugar basin in which is placed a quan- 

 tity of decaying wheat,) she takes an exact survey of every part, and selects that in which 

 she believes her ova will be best preserved, and her young larvae well cared for. In some 

 places there would be too much moisture, there the maggots would be dj-ovvned : in others 

 too little, where they would be liable to be dried up But having at length chosen a suit- 

 able locality, one neither too wet nor too dry, she protrudes her little ovipositor, and there- 

 with lays her eggs by the side of and upon one another, with the same precision that the 

 cleverest hand would arrange larger objects. She then sits perfectly still without moving 

 a member of her body excepting the ovipositor ; indeed it would appear as though she 

 were not quite conscious while the operation is being performed, for as long as she is not 

 absolutely touched one may approach her as nearly as possible without causing the least 

 symptom of alarm. During this operation which lasts from six to eight minutes, the fly 

 deposits from seventy to ninety eggs. A large number of winged insects die as «oon as 

 they have deposited their eggs, but this is not the case with MtLSca domestica : it is believed 



