Distribution — Vegetable-Feeders 299 



tropical America including the West Indies, and Mada- 

 gascar, are very nearly related to each other. Former 

 land-connections bridging the existing oceans are often 

 invoked to explain such distributional facts as these, 

 but it is more likely that the insects are the scattered 

 remnants of groups once world-wide in their range. 

 Closely allied genera of Dragon-flies inhabit Chili and 

 New Zealand, but the remains of a member of the 

 same group in the Jurassic rocks of Europe show 

 that, in all probability, these insects of the far south 

 represent the last survivors of an ancient race which 

 ages ago migrated from a northern home (l75)- 



Vegetable-Feeders. — The surroundings of any 

 animal naturally depend largely on the sources whence 

 it draws its food. The various means by which 

 Insects get their living have been often incidentally 

 referred to in previous pages. As might be expected 

 in a class so dominant and widely distributed, all 

 methods of feeding prevalent among animals are 

 practised by insects. A vast number depend directly 

 on plants for their food ; every kind of plant and 

 every part of a plant is laid under contribution. The 

 caterpillars of Moths and Sawflies (fig. 150), many 

 Beetles and their grubs, for example, feed openly 

 on leaves which they bite up with their powerful 

 mandibles and devour. Plant-bugs and Aphids get 

 their food-supply also from leaves, by piercing the 

 tissues, and thence sucking the sap. Other smaller 

 insects, as the caterpillars of many tiny Moths and 

 the maggots of certain Flics, find not food only in a 

 leaf, but shelter also, burrowing between the skin of 

 the upper and lower surfaces and eating up the soft 

 central tissue. Some of these leaf-miners form narrow 

 winding tunnels, others spread their depredations over 

 a wide area of the leaf and give rise to dry, brown 

 blisters. While the foliage leaves are thus eaten by 



