BEETLES 



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through collected specimens of weevils ?) The number of weevil species 

 is legion. The larva of all live in the inner parts of plants, whence the 

 beetles also have all essentially the same structure. The proboscis is 

 shorter or longer according as the beetle has to bore to a greater or less 

 depth before it reaches that portion of the plant which happens to serve 

 as food for its larva. 



The " worms " inside of hazel-nuts are the larvae of the bark-coloured, 

 long-snouted Nut Weevil (Balaninus nucum ; length about \ inch). The 

 maggots gnaw a hole through the shell (so-called "worm-hole") and 

 pass into the pupa stage in the earth. 



In barns and granaries considerable damage is frequently done by 

 the black corn-worm, i.e., the larva of the Corn Weevil (Calandra 

 granaria ,- length about £ inch), which devours the contents of the grain, 

 leaving nothing but the empty husks. 



Family 9: Bark Beetles (Bostrychidae). 



The bark beetles afford a remarkable illustration of what great results 

 may be achieved by the united efforts of agents individually weak. None 

 of these insects are more than a small fraction of an inch in length, and 

 they live almost exclusively on or within the woody parts of trees, their 

 food consisting of the wood, bast or bark, which they loosen with their 

 sharp mandibles (the indigestible materials remain behind in the passages 

 as "worm-dust"). A few of these beetles could hardly damage a tree 

 seriously, but when some thousands have made their nests in it, it must 

 finally succumb. By their united efforts these minute creatures manage 

 to overthrow the most venerable of our forest giants, and even devastate 

 extensive woods. 



One of the most formidable of these pests is the Common Bark 

 Beetle (Bostrychus typographus). It is about A inch in length, vary- 

 ing in colour from dark brown to straw yellow, and lives under the 

 bark of pine-trees. In the spring it seeks out a tree which seems 

 suitable for its offspring ; it gnaws its way through the bark, and erodes 

 a vertical passage or canal ("mother passage"). Lateral niches pass 

 off from this passage, in each of which the female lays a single egg. 

 The escaping larvae, which are eyeless, colourless and legless (see apple- 

 blossom weevil and others), now eat their way into the bast or bark 

 along passages running perpendicularly, or at an oblique angle to the 

 mother passage. These " larval canals " continually increase in width, 

 and finally terminate in a dilatation, the so-called " cradle," in which 

 the larva enters into the pupa condition. In the following spring the 



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