Introductory. 15 



and animal ; on dead matter, too, for that is also influenced 

 by them. 



As illustrating this diversity, let us take a particular 

 district of country, as, for instance, that in which I myself 

 dwell. Being upon the Old Red Sandstone, it is much 

 affected by ants of several species ; so much that they are 

 accounted a pest, the yellow ant ( Formica flava) certainly 

 being this. In the summers of 1878-79-80 these insects 

 swarmed upon the pastures, throwing up their " tumps," 

 deleterious to the growth of nutritive grasses ; while 

 during the summer of 81 only a few were observable. 

 This seems all the more strange from the previous sum- 

 mer being dry and warm, as one would suppose favour- 

 able to ant life, while those preceding were the reverse. 

 I have a somewhat similar record of the common house fly 

 (Musca carnaria)j whose scarcity,for several years past has 

 been notable. But though appearing early in the spring, 

 in summer it seemed to have ceased existence, while a 

 species much resembling, and commonly mistaken for it, 

 the biting Stomoxys calcitrans, was unusually abundant. 



Again, wasps, that in several previous years did much 

 damage in our pear orchards, and were even a source of 

 annoyance to mowers and reapers, in the autumn of 1881 

 were little seen or heard of. In the spring also " blight," 

 caused by grubs of countless kinds, so abounded that 

 many trees notably oaks were entirely stripped of 

 their foliage, and stood with branches bare as in winter, 

 till the flowing of the midsummer sap gave them a fresh 

 livery of leaves. For years before there had been little 

 or nothing of this larval devastation. 



Going underground to the earthworm (Lwmbricus terres- 

 tris), I noticed that for several years past my lawn was 

 remarkably clear of their castings, yet in the autumn of 



