At maturity, usually near five weeks, the full-fed caterpillar rests a day, empties the intestines, and races around searching for a suitable place to locate winter quarters.  With burrowing caterpillars that winter in pupa cases, soft earth or rotting wood is found and entered by working their way with the heads and closing it with the hind parts.  At the desired depth they push in all directions with such force that a hollow larger, but shaped as a hen’s egg, is worked out; usually this is six or more inches below the surface.  So compactly is the earth forced back, that fall rains, winter’s alternate freezing and thawing, always a mellowing process, and spring downpours do not break up the big ball, often larger than a quart bowl, that surrounds the case of the pupa.  It has been thought by some and recorded, that this ball is held in place by spinning or an acid ejected by the caterpillar.  I never have heard of any one else who has had my luck in lifting these earth balls intact, opening, and photographing them and their contents.  I have examined them repeatedly and carefully.  I can find not the slightest trace of spinning or adhesion other than by force.

With one of these balls lifted and divided, we decided what happened underground by detaining a caterpillar on the surface and forcing it to transform before us, for this change is not optional.  When the time comes the pupa must evolve.  So the caterpillar lies on the earth, gradually growing shorter, the skin appearing dry and the horns drooping.  There never is a trace of spinning or acid ejected in the sand buckets.  When the change is completed there begins a violent twisting and squirming.  The caterpillar skin opens in a straight line just behind the head on the back, and by working with the pointed abdomen the pupa case emerges.  The cast skin rapidly darkens, and as I never have found a trace of it in an opened earth ball in the spring, I suppose it disintegrates rapidly, or what is more possible, is eaten by small borers that swarm through the top six inches of the earth’s crust.

The pupa is thickly coated with a sticky substance that seems to serve the double purpose of facilitating its exit from the caterpillar skin and to dry over it in a glossy waterproof coating.  At first the pupa is brownish green and flattened, but as it dries it rapidly darkens in colour and assumes the shape of a perfect specimen.  Concerning this stage of the evolution of a moth the doctors disagree.

The emergence I have watched repeatedly, studied photographically, and recorded in the tabulated records from which I wrote the following life histories.  At time to appear I believe the pupa bores its way with the sharp point of the abdomen; at least I have seen Celeus, and Carolina, Regalis and Imperialis coming through the surface, abdomen tip first.  Once free, they press with the feet against the wing shields, burst them away and leave the case at the thorax.