( 93 ) V. Notes on the Ancestry of the Diptera, Hemiptera and other Insects related to the Neuroptera.* By Gr. Chester Crampton, Ph.D. Communicated by G. T. Bethune-Baker, F.L.S., F.Z.S. [Read March 5th, 1919.] The greater part of winged insects now living may be grouped into two principal sections, one of which, the so-called Plecopteradelphia, or Plecopteron " brother-hood," contains the lower insects more closely related to the Plecoptera — such as the Blattoid superorder (Blaltidae, Mantidae, Isoptera, Zoraptera, etc.), the Orthopteroid superorder (saltatorial Orthoptera, Phasmidae, Grylloblat-tidae, etc.), and the Plecopteroid superorder (Plecoptera, Embiidae, Dermaptera, Coleoptera, etc.), together with their fossil relatives; while the second section, the so-called Neuropteradelphia, or Neuropteron " brotherhood," contains the higher insects, more closely related to the Neuroptera — such as the Psocidae, Mallophaga, Pedicu-lidae, Hemiptera, Hymenoptera, Diptera, Mecoptera, Trichoptera, Lepidoptera, Neuroptera, etc., with their fossil relatives. In the following discussion the two sections described above may be referred to simply as the Plecopteron section (or group) and the Neuropteron section (or group). It would be extremely difficult to find any features peculiar to all of the members of one section, and not occurring in any members of the other section; but it may be said of most of the insects belonging to the Pleco-pteron section, that their mouthparts are usually strongly mandibulate and well developed; while in the insects belonging to the Neuropteron section, the mouthparts of many are slender and greatly modified. In many of the insects of the Plecopteron group there is a marked tendency toward the reduction (and, in some cases, of a thickening) of the fore-wings ; while in the insects of the Neuropteron * Contribution from the Entomological Laboratory of the Massachusetts Agricultural College, Amherst, Mass. TRANS. ENT. SOC. LOND. 1919. — PARTS I, II. (JULY)
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