428 THE BIOLOGY OF INSECTS 



and as the cause was unknown the sounds were connected 

 in the mind of the listener with the forebodings of sad and 

 anxious hours. 



Great as may be the damage caused to wooden articles 

 and structures by these beetles in the temperate regions of 

 the world, the ravages in the warmer countries of the termites 

 (*' white ants ") owing to their timber-eating habits are far 

 more serious than any due to insects of our northern 

 countries. This is a result of the alarming rapidity with 

 which a community of termites can eat a strut, a beam, 

 a large piece of furniture, or several thick volumes into a 

 labyrinth of burrows, and as the innate reaction of these 

 insects is to shun the light, they may carry on their destruc- 

 tive work unobserved until the timber that shelters them 

 collapses in hopeless ruin. Travellers in all parts of the 

 tropics have true tales to tell of buildings, goods, and furni- 

 ture apparently destroyed in a day or two, and a striking 

 example is afforded by H. M. Lefroy's record (1923) of 

 ** the wood skids and frame of the aeroplane attacked in 

 one night's hah " during the '' Cairo-to-Cape flight " of a 

 few years ago. The access of termites to the wooden parts 

 of buildings is rendered easy wherever timber is sunk in 

 the soil through which they migrate ; and the use of concrete 

 and brick foundations is to some extent a safeguard against 

 the insects' ravages. Yet they often come up from the 

 ground, covering their tracks by the construction of earthen 

 tunnels, and it is on record that they " have actually bored 

 through cement and lead " in their search for suitable 

 feeding-grounds in wood. 



In the preceding chapter several examples were men- 

 tioned of blood-sucking insects which act with the back- 

 boned animals as alternating hosts or carriers of some 

 microscopic parasitic organism, a bite by the insect drawing 

 the parasites from or injecting them into the vertebrate 

 whose blood is sought as food. Many minute organisms 

 which have such life- relations with insect-hosts are trans- 

 ferred by them into or from human blood ; thus certain 

 insects are of the most serious importance in transmitting 



