THE BREEZE FLy . 317 



nal atmosphere, such is not the case with the inhabitant of the 

 animal gall. An opening is always preserved in the upper part 

 of the sweUing, and the tail of the grub is tightly pressed against 

 the aperture so as to ensure a constant supply of air. 



In the months of May and June, these swellings may be found 

 in great plenty. They are mostly seen upon young cattle, and 

 as a general rule are situated close to the spine. So common 

 indeed are they, that out of a whole farm-stock of cattle I have 

 seen almost every cow under the age of four years attacked by 

 the Breeze Fly, and counted from two or three to twelve or 

 fourteen upon a single animal. It is said that as many as forty 

 have been detected upon a single cow, but such an event has 

 not come within my own observation. 



The swellings caused by the Breeze Fly are called Wurbles, 

 or Wornils, and can be easily detected by passing the hand 

 along the back. Strangely enough, the cow docs not appear to 

 feel any pain from the presence of these large parasites, nor 

 does she suffer in condition from them, although it would seem 

 that they must keep up a continual drain upon the system. In- 

 deed, some experienced persons have thought that, instead of 

 being injurious, they are absolutely beneficial. 



When the grub has reached its full development, it pushes 

 itself backwards out of the gall, and falls to the ground, into 

 which it burrows. Presently, the skin of the pupa becomes 

 separated from that of the larva, and the latter dies, and becomes 

 the habitation in which the pupa lives. The head portion of the 

 skin is so formed that it flattens when dry, and can easily be 

 pushed oft", like the lid of a box, permitting the perfect fly to 

 escape. Even when the insect is still in its pupal condition this 

 lid can be removed, so that the pupa can be seen within its 

 curious habitation. I may mention here that insects which are 

 thus covered while in their pupal state, so as to show no traces 

 of the creature within, are said to undergo a ' coarctate ' meta- 

 morphosis. Nearly all the diptera are examples of the coarctate 

 insects. 



Before we close the subject of parasites, it will be needful to 

 give a brief account of one or two parasitic insects which possess 



