THE DIPTERA. 6i 



larva having descended before changing. The duration 

 of this, and in fact of all the stages of the insect, depends 

 entirely upon the temperature, but the females invariably 

 deposit eggs, even during the hottest weather, and are 

 never ovo-viviparous like the next species, and several 

 others of the genus. 



Family MUSCID^:. 

 SarcopJiaga Icemica (Plate VII., fig. 10). 



Another extremely abundant species having a similar 

 history to the last, but its powers of development are 

 very much accelerated owing to the larva being positively 

 born alive. The females hover over meat and other 

 suitable substances, depositing a number of minute wrig- 

 gling maggots thereon, not infrequently to the great 

 disgust of some hungry individual, who perhaps is making 

 his dinner off a mutton chop which the fly has selected 

 as a home for her offspring. These larvae are all pro- 

 duced from distinct ova, which hatch before being laid, 

 as I have often proved, by removing them from the 

 insect's abdomen, and watching the young larva emerge 

 from a minute elliptical white egg, covered with a thin 

 leathery skin. Every one who has travelled in New 

 Zealand must have noticed that, in the wildest spots, 

 these insects assemble in large numbers as soon as any 

 meat is uncovered, thus not only showing their universal 

 distribution throughout the country, but also that they 

 possess a very keen sense of smell. 



Two British species at least, allied to this genus, have 

 been introduced into New Zealand, viz., Mttsca domestica 

 and Musca azsar. The former is probably a world-wide 

 insect, every ship teeming with it, but the latter is 

 at present rather scarce and is usually found in the 

 neighbourhood of farm-yards, where the larva feeds on 



