190 PKACTICAL PAEASITOLOGY 



microscope upon a glass slide in a drop of normal saline solution. The 

 head is held firmly by means of a needle held in the left hand and 

 inserted into the groove of the antenna. If, with the right hand, a 

 second very fine needle is now inserted diagonally beneath the edge 

 of the 3rd or 4th abdominal segment, the greater part of the abdominal 

 wall may be pulled apart and the viscera will be exposed. 



(4) Diptera. Of the larvae of Diptera, those of Muscidse are 

 occasionally, those of (Estridae permanently, parasitic in their habit. 

 These larvae are commonly known as " maggots," and are readily 

 obtained by exposing a piece of raw meat or the dead body of a small 

 mammal to the air. In summer, decomposition soon sets in, and the 

 smell of putrefaction will attract flies of several different species, 

 which are in search both of food and of a suitable place in which to 

 deposit their larvae or eggs. The varieties most commonly met with 

 are the blow-fly, Calliphora vomitoria (L.), and the very similar 

 C.- erythrocephala (Meiz.), and the meat-fly, Sarcophaga carnaria (L.). 

 The Calliphora varieties deposit eggs, while the Sarcophagidae are 

 viviparous. The larvae of the cheese-fly, Piophila casei (L.), which 

 perform springing movements, are found in decomposing cheeses of 

 the softer kind ; those of Teichomyza fusca (Macq.), which are flat in 

 shape and forked at the hinder end, are found in decomposing urine 

 and in earth which has become soaked with it ; the larvae of the 

 house-fly, Musca domestica, L., occur principally in dung and other 

 excrements, where the larvae of other species, notably those of 

 Homalomyia, are also usually forthcoming. The larvae of Homalo- 

 myia are flat, the segments being furnished upon each side with 

 feathered appendages ; they are generally found in rotting animal 

 and vegetable substances. 



The rearing of these larvae artificially is usually a simple matter. 

 The substance containing maggots should be kept upon the ground ; 

 it should be kept sufficiently damp ; and should be covered over with 

 wire gauze. 



The larvae of Calliphora, Sarcophaga, and Musca are very similar 

 in appearance. The cylindrical body, which is pointed in front and 

 cut off sharply at the back, shows distinct segmentation. At the 

 pointed end, the hard parts of the oral cavity appear as brownish- 

 black marks ; the anterior edges of the segments bear circular ridges 

 of a brownish colour ; and there are two brown points upon the blunt 

 posterior end. These markings will be clearly seen if the larvae are 

 killed with hot water or hot 70 per cent, alcohol, and examined, either 

 with a magnifying glass or with a microscope fitted with a low power 

 lens, the object being lighted from above. The dark colour of the 

 segmental ridges is seen to be due to the presence of numerous 

 minute thorns, while the dark points at the posterior end reveal them- 

 selves as small oval scales which in, Calliphora and Sarcophaga, have 



