416 



ANIMAL BIOLOGY 



and Man. The cause of pebrine proved to be a Protozoan parasite, 

 Xosema bombycis. (Figs. 214, 267.) 



The dependence of many plants upon insects for pollination is 

 well illustrated by the difficulties in establishing the Smyrna Fig 

 in California. The fruit would not mature, and studies by botanists 

 and entomologists showed that in the plant's native land pollina- 

 tion was effected by a certain tiny insect. Importation and es- 



C 



Fig. 267. — Silkworm Moth, Bombyx mori. A, caterpillar; B, cocoon; 

 C, male moth; D, female moth. (From Shipley and MacBride.) 



tablishment of the insect carrier in California created there the 

 immense fig-growing industry. (Fig. 219.) 



As a matter of fact an amazing number of plants that we most 

 highly prize would be unable to reproduce were it not for pollina- 

 tion by insects: for instance, there would be no pears, apples, 

 peaches, plums, oranges, or strawberries. So it is perhaps not 

 unreasonable that an entomologist has asked whether insect dep- 

 redations may not be regarded as a twenty per cent commission 

 we pay for the invaluable services that "friendly insects" render. 

 It may, but it is economical, if not generous, to reduce the tax 

 to the lowest limit! 



Insects touch human affairs in other vital but less direct ways. 

 It will be recalled that Darwin emphasized the importance of 

 Earthworms in aerating and plowing the soil; but various insects 



