342 Insects and their Surroundings 



wooden buildings, are a source of positive danger. 

 More intimate and unpleasant relations with man are 

 established by those insects which, like Gnats, Fleas, 

 Lice and Bugs, draw their food-supply from his body. 

 Flies of the family Muscids are now well known 

 to serve as carriers of disease-germs, and the bite 

 of a Mosquito often injects the micro-organism of 

 malaria into the human blood-system. The maggots 

 of flies however must generally be regarded as of 

 considerable indirect service to man, by devouring 

 decaying substances which might otherwise cause 

 serious disease. In the same way the action of the 

 Silphidee and other carrion-feeding beetles is highly 

 beneficial. And if some insects destroy fruit-trees 

 others, specially Bees, by their action on the flowers, 

 ensure the ripening of the fruit. 



Comparatively few insects can be recognised as 

 directly serviceable to us. Some species are habitu- 

 ally eaten in warm countries — locusts in the East, 

 and water-bugs in Mexico. Several kinds of soft- 

 skinned beetles have been used medicinally to raise 

 blisters ; the gall of a south European Gall-fly 

 (Cyfiips tinctoria) serves in the manufacture of ink, 

 but its use is now largely supplanted by chemical 

 processes. A Scale-insect (^Coccus cacti) produces the 

 well-known cochineal red dye, while to another insect 

 of the same family (Carteria lacca) we are indebted 

 for lac. Of very great importance is the Common 

 Silkworm (fig. 66), the caterpillar of the moth Bombyx 

 mori (fig. 136), so largely cultivated in southern 

 Europe ; as also the caterpillars of several large 

 Saturniid moths which are reared in the east for 

 purposes of silk-production. To the secretion of 

 these caterpillars we owe the immense quantity of 

 silk used in commerce and the arts. And lastly 

 we have in the Hive-bee a thoroughly domesticated 



