614 INSECTS AT HOME. 



The last-mentioned fact is a very curious one, as all will 

 admit who have dissected insects. I have dissected a vast 

 number of insects, representing every order, and nearly every 

 important group in entomology, but I never diss-scted a 

 Stratiomys, and never saw the remarkable structure which 

 Mr. Walker mentions. 



When the larva is about to undergo its change to the pupal 

 form, the larval skin hardens, without much alteration of its 

 shape, and vathin this cover the pupa becomes developed. 

 Being much smaller than the larva, the pupa only occupies a 

 portion of the larval skin, so that a. large space is left, render- 

 ing the pupa and its case much lighter than water, and 

 enabling it to float at liberty on the surface. 



We now come to the next group, or Stirps, of the Cephalote 

 Diptera. They are called Tanystoma, or Long-mouthed Flies, 

 in consequence of the construction of the mouth, which is 

 generally very prominent, and is furnished with a lancet-like 

 labrum and tongue. The larvae are very worm-like, without 

 feet, and having the head hard and scaly. They live under- 

 ground, and there pass through their transformations, as we 

 shall see in our short history of the following insect. 



On Plate XX. Fig. 1 is represented the Gteeat Breeze Fly, 

 GrAD Fly, or Cleg {Tahanus bovinus), one of the largest of our 

 Dipterous insects. Its colour is rather variable, but its general 

 effect is brown, sometimes deepening into dark-brown and yellow, 

 with chestnut triangular marks down the centre. It has very 

 much the aspect of a large bee, and its wheeling flight and 

 loud hum serve to strengthen the similitude. The mouth is 

 armed with most formidable lancets, and the insect, at least the 

 female Breeze Fly, can employ them with terrible effect. The 

 tough skin of cattle is no defence against the lancets of the 

 Breeze Fly, and the very hum of one of these insects is able 

 to set a whole herd of cattle scampering off in every direction. 



Even human beings are not exempt from the attacks of the 

 Breeze Fly, as I can aver from much experience. Some years 

 ago I was spending a week or two in the New Forest, and 

 would have enjoyed it without alloy, had it not been for the 

 Breeze Flies, which almost drove me out of the Forest. Tliey 

 seemed to detect me at a wonderful distance, and, with a load, 



