Clapp tẹsiwaju awọn ẹkọ postgraduate rẹ ni ile-iwe Louis Agassiz's Anderson School of Natural History on Penikese Island, Buzzard's Bay, MA ni 1874. O gba ọrọ Agassiz's "Ikọ ẹkọ iseda, kii ṣe awọn iwe!" o si lo o si ẹkọ tirẹ. O ṣafihan imọ rẹ nipasẹ ẹkọ ẹkọ ti o wa ni Mount Holyoke, ti o rọpo nipasẹ awọn ayẹwo lati ọdọ awọn alumni ni ilu okeere. Pẹlú pẹlu awọn onimọran New England miiran, Clapp gba awọn kokoro lati White Mountains ti New Hampshire ni ooru ti 1875 ati lati awọn ipinlẹ arin-Atlantic ni 1877. (Stops pẹlu ibudo Johns Hopkins ni Beaufort, ati Ile-iṣẹ Smithsonian ni Washington D.C.)
ìpínlẹ̀ New Hampshire