Psocetae

Introduction

The four families of Infraorder Psocetae are all bark or stone surface dwellers. These insects are 2-8mm long and eat lichens, algae, and fungus.

Characteristics

• General appearance:
  • Medium to large in size, about 3-8 mm.
  • Coloration variable, but usually whitish in ground colour and with dark brown markings.
  • All bark or stone surface dwellers.
• Head with rounded vertex
  • postclypeus not strongly bulged
  • internal ridge of epistomal suture narrow
  • anteclypeus sclerotized
  • male eyes usually much larger than female's
  • ocelli complete, not clustered on small tubercle
  • mandible short, outer margin smoothly rounded, posterolateral margin not hollowed
  • lacinial tip variable
  • galea flattened
  • labial palpus rounded
• Thorax
  • prothorax less bulged dorsally
  • pterothorax greatly bulged dorsally
  • median part of mesoscutellum pentagonal
  • mesothorax with narrow precoxal bridge and broad trochantin
  • membranous region of metaepisternum broad.
• Forewing often with dark brown markings
  • posteroproximal corner smoothly rounded
  • veins and wing margin glabrous
  • top of CuA1 usually connected with M except free in Psilopsocidae
  • A2 never present.
• Hindwing glabrous, posteroproximal corner smoothly rounded
  • Sc clear Rs and M , Cu fused for long distance basally
  • Rs and M fused or connected by crossvein (some genera in Myopsocidae).
• Legs
  • hind tarsus with row of broad ctenidia based setae (condition of this character in Psilopsocidae not examined or documented)
  • tarsi 2- or 3-segmented claws with preapical tooth pulvillus broad or narrow (Psocidae).
• Abdomen without eversible vesicles ventrally.
• Male genitalia:
  • paraproct with process on distal margin.
  • hypandrium usually with complex distal processes or lobes.
  • phallosome variable
  • internal valve present or absent external valve often absent
  • endophallus lacking sclerotized portion.
• Female genitalia:
  • paraproct with cylindrical distal projection.
  • subgenital plate with 1-lobed egg guide extending from ventral margin
  • apex of egg guide usually bearing setae.
  • gonapophyses complete and variable in structure
  • external valve internally expanded.

Discussion of Phylogenetic Relationships

The monophyly of Psocetae is supported with molecular data (mtDNA genes 12S, 16S, and COI and 18S rDNA; Johnson & Mockford 2003). Morphological data have excluded Hemipscoidae from the infraorder, however, based on four characters (from Yoshizawa 2002):

• absence of the epistoma suture
• broadened first axillary sclerite
• two-branched M vein in forewing
• a CuA1-M crossvein in forewing.

References

Yoshizawa, K. 2002. Phylogeny and higher classification of suborder Psocomorpha (Insecta: Psocodea:'Psocoptera'). Zoological Journal of the Linnean Society 136: 371-400.