THE Cows THAT ANTS MILK 13 



thus leaving the two insects, the parasite and the 

 carnivore, to fight it out in their own way between 

 them. 



But No. 5 introduces us to a still more insidious 

 though less dangerous foe : an internal parasite 

 which lays its eggs inside the body of the bud- 

 producing female. There the grub hatches out, 

 and proceeds to eat up its unwilling hostess, alive, 

 from within. In the sketch, we have an illustration, 

 below, of an aphis which has thus been compelled 

 to take in a stranger to board and lodge in her 

 stomach ; while the top figure shows how the 

 lodger, after eating his hostess out, eats himself out 

 into the open air through her empty skin. If you 

 look out closely for such haunted green-flies, in- 

 habited by a parasite most often an ichneumon 

 fly you will find them in abundance on the twigs 

 of rose-bushes. They have a peculiar swollen, 

 quiescent look, and a brownish colour. 



No. 6 shows us another such fierce enemy at 

 work. This formidable insect tiger is the larva of 

 the wasp-fly ; he is a savage carnivore, who moors 

 himself by his tail end, stretches out to his full 

 length, and swoops down upon his unsuspecting 

 prey from above ; and being blessed with a good 

 appetite, he can get rid of no fewer than 120 

 aphides in an hour. As he probably eats all day, 

 with little intermission for rest and digestion, this 

 gives a grand total of about 1500 or 1600 victims 

 at a sitting. However, the remaining aphides go 

 on budding away as fast as ever to make up the 



