Note 73 — PART I.—MORPHOLOGY AND PHYSIOLOGY (continued 11)

In the Hymenoptera the two pairs on the meso- and metathoracic segments are open in the Aculeata, also in the Siricidæ, among which sometimes that on the third segment is closed. In Pimpla and Microgaster (fully grown larvæ) only the mesothoracic stigmata are open.

Palmén adds that most dipterous larvæ are amphipneustic; Cecidomyia, the Mycetophilidæ, Bibionidæ, and Stratiomys are typically peripneustic. (p. 92.)

Moreover, a single insect, as Sialis, may be apneustic as a larva, peripneustic as a pupa, and holopneustic in the imago stage.