DRAGON-FLIES AND OTHER INSECTS. 247 



out backwards with considerable force, the insect is 

 thrown forwards with a spring. Dark lead-coloured 

 individuals of this group may be sometimes seen in 

 immense numbers in roadside puddles, or by the 

 margin of ponds, like grains of gunpowder. Other 

 species are found but few together and almost solitary. 

 Some controversy has of late years been carried on as 

 to the true interpretation of the marking on the scales 

 with which many of the species are furnished, and in 

 these communications they are spoken of as Podura 

 scales, althpugh that general term includes two or 

 three different genera. It is sufficient for our purpose 

 to call them Poduridce. They appear to be very par- 

 tial to mites as food. 



The "world of insects" is not a mere phrase, it is a 

 reality, of which we have taken but the poorest 

 glimpse. To know all the inhabitants of this world, 

 even by name, is the work of a lifetime, but what of 

 their structure, their economy, their loves, their lives, 

 their instincts ? These are mysteries of which we have 

 as yet learnt but little, compared with what remains 

 to be known. If any man be vain of his knowledge, 

 thinking himself wise, let him but visit the " world of 

 insects," and question himself which is the greatest, 

 his knowledge or his ignorance. 



