220 NATURE STUDY. 



world, and not fewer than three hundred species in North 

 America alone. 



The mosquitoes, the midges, the gnats, the dance-flies, 

 the black-flies, the horse-flies and the flesh-flies all belong 

 to the order Diptera and are separated into many families, 

 but it is not easy to distinguish them until one has become 

 well advanced in the study of entomology, and boys and 

 girls will not commonly make large collections of them, or 

 of the two-winged insects generally. 



Plant Mimicry. 



The quaintest of all fungus pretenders are those which mimic 

 birds' nests and are known as the bird's nest fungi. There are at 

 least three different sorts of fungus which pretend to be nests. 

 The resemblance is the more extraordinary in that the little round 

 fruits of the fungus lying inside the cup-like nests look exactly 

 like eggs. Perhaps the strangest part of it all is that botanists 

 have never yet succeeded in discovering the reason of this mimicry 

 on the part of the bird's nest fungi. 



The plant worm of New Zealand is another fungus oddity which 

 for a long time puzzled men of science. It grows from the body of 

 the grub of the bulrush caterpillar and at first sight appears to be 

 a small bulrush. Stalk and head show a perfect resemblance to 

 the plant. But the seeming bulrush is a fungus pure and simple, 

 of which the spore has settled in the body of the unfortunate cat- 

 erpillas. As it grows it absorbs the body of its host, but it takes 

 nothing from the ground, as it would if it were indeed a real plant. 



A great many people imagine that the oak apple is a fruit of the 

 oak tree, for when it is fresh it bears a strong resemblance to a 

 small rosy-tinted apple. 



But here again the tree deceives us. The oak apple is a gall or 

 disease caused by certain insects which pierce the bark and instill 

 a sort of poison, causing a gall to form, which protects and makes 

 food for their young. — London Atts7vcrs. 



