450 



environment, it will be profitable to coni])are the entomological ecology 

 of this introduced but long-established and widely cultivated plant with 

 that of some native species which is also generally and. in some districts, 

 extensively grown. 



We may take for this purpose the strawberry plant, whose insect 

 visitants and injuries I studied carefully several years ago. About fifty 

 insects species are now listed as injurious to tlie strawberry and about 

 twenty of these also infest corn. Two fifths of the known strawberry 

 insects are thus so little specialized to that food that they feed on other 

 plants as widely removed from the strawberry as is Indian corn. On the 

 other hand, six species, all native, are found, so far as known, only, or 

 almost wholly, on the strawberry, at least in that stage in which they are 

 most injurious to that plant. These are the strawberry slug (Einl^liyttts 

 niaculatiis) ; the strawberry leaf-roller (Phoxoptcris comptaiia). occa- 

 sionally abundant on blackberry and raspberry, to which it spreads from 

 infested strawberry plants adjacent; two of the strawberry root-worms — 

 the larvae of Typophorus atcrrimus and of Scelodonta ncbiilosiis; the 

 strawberry crown-borer ( Tylodcrma fragaria) ; and the strawberry aphis 

 {Aphis forhcsi). 



Not even one of this considerable list exhibits, so far as I can see, 

 any special structural adaptation to life on the strawberry plant. The 

 two root-worms mentioned, for example, are no better fitted to feed on 

 strawberry roots than is a third strawberry root-worm — the larva of 

 Colaspis brmnica which lives on the roots of corn and timothy also. 

 Emphytiis Diaailatits might feed, for all the structural peculiarities which 

 one can see. on the leaves of roses as well as does the common slug or 

 false-worm of those shrubs, and so of the others of the list. Even the 

 strawberry crown-borer, which lives in all stages solely on that plant, 

 might, so far as structure and life history are concerned, feed and de- 

 velop in any other thick-rooted perennial. The difference seems to be 

 one of habit or preference solely, and not of structural adaptation. 



Our impressions of the extent, nicety and frequency with w^hich in- 

 sects and plants are mutually adapted are indeed commonly much exag- 

 gerated, owing to the fact that our attention is especially drawn to notable 

 cases of curious, precise or particularly advantageous adjustments be- 

 tween organisms, while no general study is made of the entire system of 

 relations obtaining between all the members of an associate group, vary- 

 ing vv'idely. as these do. in respect to the intimacy, importance and exclu- 

 siveness of the association. For this same reason in part, we ordinarily 

 have no accurate idea of the relative frequency and primacy of structural. 

 or static, adaptations — particularly obvious,' especially interesting, and 

 seemingly ingenious as they often are — and of those more obcure adap- 

 tations of preference, behavior, habit and the like, which, taken together, 

 we mav call dynamic. 



