MAN'S ACCOUNT WITH THE LOWER ANIMALS 9 



in boring into the grains produces much larger quantities of 

 flour than it consumes, and the surplus is used by the larvae 

 until they manage to make their way into some grain and 

 begin milling operations on their own account. 



A very different species, though again a beetle, is Trogo- 

 derma Jckapra. The perfect insect somewhat resembles a small 

 ladybird and is a harmless little creature which apparently 

 need not feed at all ; at any rate it does not attack sound grain 

 and is very short-lived. The larva, on the other hand, is one 

 of the most serious of the grain-pests in India, and extreme 

 care ought to be taken that it is not accidentally introduced 

 into other countries warm enough to enable it to thrive. It 

 is so different from the other grain-pests in appearance that 

 it has received a special name from the Indian natives, who 

 speak of it as khapra, while all the different kinds of adult 

 beetles seem to be lumped together under the term susri 

 (Barnes and Grove). The larvae are characteristically hairy 

 and lead an active life, moving about between the grains and 

 attacking them by gnawing the surface. Their cast skius 

 accumulate in immense numbers on the surface of the grain 

 and soon indicate the presence of the pest. 



Of the secondary grain-pests, which do not attack whole 

 grains but feed upon the detritus produced by the activity 

 of other insects, the commonest are perhaps the red flour- 

 beetle (Tribolium castaneum), the saw- toothed beetle (Silvanus 

 surinamensis) and species of Laemophloeus. These are all 

 very easily cultivated in jars of broken wheat and form 

 very convenient subjects of study for those who are 

 interested in insect life -histories. They increase at an 

 enormous rate and under favourable conditions the jars are 

 soon teeming with the worm-like larvae in all stages of develop- 

 ment, together with pupae and perfect insects. They seem to 

 be incapable of maintaining themselves in sound wheat and 

 all should probably be regarded as flour-beetles rather than 

 as true grain-beetles. 



In many of my cultures large numbers of very beautiful, 

 minute, winged, fly-like insects make their appearance. These 

 are hymenopterous species related to the ants, bees and 



