Page:The Gall Wasp Genus Cynips.pdf/28

 in all the fields and woodlands and mountain forests thru which we journey at many miles an hour, for hour after hour, yesterday, today, and tomorrow. Nevertheless, our samples seem typical, for they are surprisingly uniform; and after such field experience, one comes to feel there is a reality summed up in the word “species” which is more than a few cabinet specimens or a bottle full of experimental material or a Latin binomial in a textbook. It is an existent, tremendous population of living individuals whose identities and dissimilarities, whose divergences from all other populations, whose origin in some remote past and extension thru actual generations and years of time, whose position on these particular trees in these particular valleys and everywhere over these miles of actual country—it is this reality which, to us, constitutes the species problem.

But we have met erinacei everywhere across the miles of Indiana and across Ohio. This morning we found it in the stream valleys and over the hillsides of West Virginia. At noon we still found it in more rugged country in the heart of the mountains, and now, near the end of the day, our road-signs read Maryland and we know we are near the crest of the Alleghanies. We get out of the car and climb the hillside. It is thick woodland and we find only stray galls now and again. They are smooth and naked specimens, for aught we can tell like the smooth galls of erinacei. A mile down the road we find an open meadow where two isolated trees offer promise of richer collections. The farm boy helps, and we collect more smooth galls while we wonder about the varied mixture which spreads so many miles back of us. It is drizzling now, and sheets of fine snow come whirling off the mountain, but we espy a tree in the next open, and in the gathering dusk find—many naked but only two spiny galls for our collections! We return to the car, wondering what is the matter with the sample.

Before we sleep that night we shall have worked our way down into the valley of the Potomac. On the next day we shall collect across the valley of the Shenandoah, and in the days that follow out onto the sand coast of Virginia and southward along the shores of the Carolinas. Within a few months we shall breed the insects from the smooth galls we gather, and then we shall know that from the Maryland line to the