ENTOMOLOGY-HYMENOPTERA.
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closed or effaced spiracles in the following segments. The position of thegills, accordingly, is as uncommon as their presence at all in a perfectinsect. The pupa has the gills likewise, only still more developed. Pictet has remarked that the larva; throughout this family have gills on the chest,with the exception of Perla virescens and nigra, which would seem toindicate a different mode of life in these species. The same is the case withthe pupae of Pteronarcys regalis and Perla abnormus, Newm., respectively.According to Mr. Barnstone’s observations, the former lives in the water at thebottom of the river, the latter in the chinks of the float-wood, and trunksof trees, upon the banks, &c. Pt. regalis is a nocturnal insect, lurking byday in damp places under stones. Consequently it may breathe through itsgills, as it is not indispensable that these should be in immediate contactwith water, they perform their function equally well if the air is only moistenough to keep them pliant. A closer anatomical examination will benecessary to determine whether it possesses tracheae also, for thoughthere are orifices on the underside of the chest, they are in an unusualposition, in the middle of the respective breastplates (sterna), partly betweenthe hips, and it is questionable whether they communicate with traclie®.The presence of gills seems to be one of the distinctive characters of thegenus Pteronarcys, as they have been found in Pt. regalis, biloba, proteus,and in an undescribed species. In dried specimens they shrink up and areoften lost, though their existence can usually be ascertained.
Libellulina:. —Selys Longchamps (ltev. Zool. 135) has discovered anew European species of Cordulegaster, and has distinguished it, as C. biden-tatus, from C. annulatus, which it much resembles.
Hagen has endeavoured to prove that the Libellula vulgaris of Linnaeus is Donovan’s L. scotica (Ent. Zeit. 257); subsequently (p. 290) he has shownthat L. cancellata, L., which Zetterstedt has referred to L. scotica, Don.,belongs in reality to the species commonly known for it [A. lineolata, Charp.],and that the name scotica must be retained, as the oldest, for the otherspecies [ I. nigra, Charp., Burm.]