Febeuaey 17, 1899.] 



SGIENGE. 



243 



importance, since it must be plain that of 

 the natural agencies by which cross-fertili- 

 zation of plants is accomplished insects are 

 far and away the most prominent. Every 

 investigation which has been undertaken 

 of recent years, and activity in this field is 

 increasing by leaps and bounds, has shown 

 the most marvelous adaptations between 

 the structure of flowers and the structure 

 of their insect visitants, all in the line of 

 facilitating or really enforcing the collect- 

 ing and carriage of pollen by flower- visiting 

 insects from one plant to another. An esti- 

 mate of the numbers of the species of insects 

 engaged in this work would include the 

 forms belonging to whole families and al- 

 most orders, and if we could imagine the 

 race of flower-visiting insects wiped out of 

 existence the disastrous efl"ect upon plant 

 growth would be beyond estimate. I am 

 not prepared to state that insects benefit 

 plants in this way to such an extent as to 

 overcome the results of the work of the 

 plant-destroying species, but if it were pos- 

 sible to compare in any way the results of 

 these two classes of work it is safe to say 

 that the effect would be surprising. 



We must, therefore, without going further 

 into detail , place this pollenization of plants 

 as one of the very most important beneficial 

 functions of insects in their relations to 

 man. 



AS SCAVENGERS. 



Another beneficial function of insects, the 

 importance of which can hardly be overesti- 

 mated, is their value to humanity in doing 

 away with, and rendering innocuous, dead 

 matter of both plant and animal origin. 

 This subject has never been discussed with- 

 out reference to the famous statement by 

 Linnseus that the offspring of three blow- 

 flies would destroy the carcass of a horse 

 as quickly as would a lion ; and while the 

 exact statement in its details is open to 

 doubt, still it serves to illustrate, in a strik- 

 ing way, the good offices of insects, and it is 



certainly true that after the offspring of the 

 blow-fly have finished with the horse's car- 

 cass this would be left in a much less offen- 

 sive condition than after the departure of 

 the lion. 



There are inhabited regions in which the 

 climate is so dry that dead bodies of ani- 

 mals never become offensive, but, by natural 

 mummification, remain simply as cumberers 

 of the earth. In such regions insects play 

 little part. Wherever, however, there is 

 sufficient moisture to produce a natural de- 

 cay, there insects occur in swarms and 

 hasten the destruction of the decomposing 

 mass in a marked degree. Were the bodies 

 of dead animals not destroyed by insects in 

 this way, and, still more, were the destruc- 

 tion of dead vegetation not hastened as it 

 is by the attacks of countless insects, it is 

 perfectly easy to see that the earth would 

 not be inhabitable, its surface would be 

 covered with the indestructible remains of 

 what was once life in some form. 



Large groups of insects, comprising many 

 thousands of species, take part in this in" 

 estimable work, and it will probably be un- 

 necessary in order to bring about a realiza- 

 tion of this value to dwell further upon the 

 subject. 



AS MAKERS OF SOIL. 



It is a fact not generally realized that 

 insects must take an important part in the 

 changes in the character of the soil which 

 are constantly going on. Occurring in such 

 countless millions, as they do, constantly 

 penetrating the soil in all directions, fre- 

 quently dragging vegetation below the sur- 

 face and bringing the subsoil up to the 

 surface, changing the character of the soil 

 humus by passing it through their bodies, 

 and fertilizing the earth by their own death 

 and decay, it is probable that insects are 

 responsible for even more soil change than 

 are the earth worms, which Darwin has 

 placed before us in such an important light. 



Insects are found beneath the ground in 



