SATYKINAE: OENEIS SEMIDEA. 147 



affected, and by tlie time the tree line was reached (about 4500') the wings 

 ot"oj)[)()site sides diverged at an anf(le of 30°, as if they were lips parted and 

 gaspin<>; for air. T^ater they began to walk about, and when they stopped 

 would tightly close their wings (as by habit) for about a minute, and 

 then would slowly part them again, — in one case to as much as ()0°— 70°. 

 At the bottom (2800') I thought them dead, for they lay ^vith parted 

 wings upon their sides, but they gradually revived slightly. Still, when 

 I set them free and tried to startle them only one would move ; she flut- 

 tered two or three times and tried to fly away, but could not leave the spot 

 where she ineffectually tossed up and down ; I caged them again and 

 they walked and fluttered about a little, but gaining n(^ strength at the 

 end of twelve hours they were killed. The difference in temperature at the 

 two extreme levels was not worth consideration. 



Now there are many other butterflies, denizens of the lower levels, which 

 continually fly to the summit of Mt. Washington, and doubtless descend 

 again. Polygonia faunus is one of these, and accordingly I carried down 

 in company with semidea as many females of this species, together with 

 some males, captured on the summit ; but not caring to observe them close- 

 ly on the way, they were enclosed in pocket boxes and let loose immediately 

 on arri\al at the base ; they flew away w ith all their vehement vigor, not in 

 the slightest incommoded by the sudden change. 



I queried whether there could be any organ in the body which might 

 have a different construction or amplitude in these two butterflies, which 

 might serve as a better means of adaptation to differing air pressure in the 

 one and the other, as the swimming bladder is known to do in some fishes. 

 The only special organ I could think of was the so-called food reservoir, 

 which, though furnished within, as shown by Burgess, with an arrange- 

 ment of clustered hairs which seems adaptable for use in digestion, is nev- 

 ertheless usually empty on dissection, and might receive air as well as 

 honey through the apparatus at the mouth. But the dissections of the 

 two species made for me by Mr. Emerton (61:47,50) do not lend much 

 help ; the organ is indeed larger in faunus than in semidea, but the dif- 

 ference does not seem to be very significant. 



Parasites. Notwithstanding the physical difficulties with which this 

 frail butterfly has to contend, it still has its full share of parasitic enemies, 

 and they seem at times so numerous that one wonders how the creature can 

 withstand this added source of evil. There is first a large Ichneumon, 

 I. instabilis Cress., oidy one of which can live on one fat Oeneis, and 

 which emerged from a wintering chrysalis on June 23, Xext there is a 

 Pteromalus, P. chi(mobae How., of which a single caterpillar may harbor 

 a considerable number ; those which I obtained emerged from the chrysalis 

 on August 9 ; but on one occasion, I took twenty-five of their pu[)ae 

 from a sino-le chrvsalis and found that each had been itself attacked bv a 



