On the abdomen there are several chitinous hooks, which serve in some sort as substitutes for limbs. By their means the pupa can moor itself to the stems of aquatic plants; and this is necessary, since its specific gravity being less than that of the water it would be always at the surface, if it had no such means of anchorage. And of course, at the top of the water, it would be exposed to the danger of being snapped up by birds. De Geer’s specimen passed six days in the pupal state, and then emerged as a perfect Crane-fly. My specimens did not emerge till after ten and eleven days of pupahood, which seems strange, as they were plentifully supplied with food in their larval stage. The fly is a little more than half an inch long, and may be distinguished from the common Daddy-longlegs by the character of the wings, which are folded somewhat like those of a wasp, but with this difference: that the wings of this fly are folded outward, while those of the wasp are folded inwards. When the insect wishes to fly, it opens the fold so that the whole wing presents a plane surface, but the fold reappears directly the Crane-fly ceases its flight (Frontispiece). [Illustration: FIG. 81.--Fore-wing of Bee, showing marginal fold (× 7).] De Geer’s allusion to the wing of the wasp might have been extended to most of the Hymenoptera, as we may see by examining the fore and hind wings of a bee or a sawfly. Dr. Sharp[63] says, ‘The wings [of the Hymenoptera] are remarkable for the beautiful manner in which the hinder one is united to the anterior one, so that the two act in flight as a single organ. The hind wing is furnished with a series of hooks, and the hind margin of the front wing is curled over so that the hooks catch on to it. In some of the parasitic forms the wings ... have no hooks. The powers of flight, in these cases, are probably but small.’ If we were taking our subjects in consecutive order, the larva of Ptychoptera would properly come here, as being that of a Crane-fly. But since it will be convenient to examine another larva which resemble Limnobia in its breathing apparatus, we will take next the larva of _Parap´onyx stratiota´ta_, one of the China Marks, for it is extremely interesting and by no means hard to come by. The China Marks are small moths, with white wings bearing dark markings, which have been supposed to resemble Chinese characters. Their larvae are aquatic in varying degree--that is, some breathe air in the usual way, by means of spiracles; while others, by means of gills, breathe the oxygen dissolved in the water.