222 INSECTS AND MAN 



lice, large lice, begot of your own bodies and the heat of 

 the brick-kilns." These insects have also been made use of 

 in cases of atrophy and quartan fever. 



Many other insects have undoubtedly paid tribute at the 

 shrine of Hygeia, but the practice of using them as drugs 

 is on the wane. Formic acid is no longer manufactured 

 from ants, but is made artificially. Cantharides has many 

 rivals as a blistering agent. It is in country districts, 

 where old customs die hard, that the remedies of our 

 forefathers are most likely to be encountered. Chemical 

 research and medical science have inflicted other nostrums 

 upon us, though none more efficacious, if we can believe a 

 moiety of all that is claimed for those that have passed. 



SOME USEFUL SCALE INSECTS 

 The Lac Insect 



Scale insects, as a family, are looked upon with great 

 disfavour by economic entomologists. One member of the 

 family, however, by its general utility, does a little to 

 retrieve the bad name of its relations : the individual is the 

 lac insect, Tachardia lacca. When it is realised that the 

 value of the export of lac from Indian ports, in a single 

 year, has totalled, approximately, thirty-three million 

 rupees, it will be gathered that the cultivation of the lac 

 insect is an important industry. A word or two concern- 

 ing the origin and nature of lac and some information 

 about the industry itself may not be out of place. Lac is 

 the resinous secretion of a scale insect. Like other scale 

 insects, the lac insect is provided with a sucking beak, 

 which it inserts into the tree on which it lives and from 

 which it draws up the sap. These insects have been likened 

 to animated siphons, in that the imbibed sap, after modifica- 

 tion and partial absorption, is given out as a secretion at 

 the anal end of their body. On contact with the air this 

 secretion solidifies, forming the " scale " which is popularly 



