Trichopsocus

Introduction

The family Trichopsocidae contains 9 species in the genus Trichopsocus distributed worldwide, but absent from Asia. Two species are known from North America; Trichopsocus acuminatus, introduced from Europe, and T. dalii, introduced from Italy, Peru, and Mexico.

These are medium-sized bark lice (2-2.5 mm, nymphs also 2-2.5 mm) with slender bodies.  Body color is yellow. Trichopsocids inhabit leaves on living and dead trees.

Characteristics

Synapomorphies

• Hindwing veins Rs, M, and Cu are not fused at base.
• Female: subgenital plate without distal extension.
  

General Characters

• Head: Antennae have 13 segments.
• Legs: Tarsi have 2 segments.
• Wings:
• Forewing veins with "Caecillius" pattern:
• Areola postica is free of vein M.
• Veins Rs and M are usually fused for part of their length.
• Forewing hairs:
• Hairs on margin of forewing do not cross each other.
• Forewing veins have one row of hairs.
• Hindwing
• Hindwing veins Rs, M, and Cu are not fused at base.
• Hairs are present on magin but absent from veins.
• Abdomen:   
  
• Adults have one abdominal vesicle (small inflatable sac) on abdominal segment 6/7
• Nymphs have two abdominal vesicles: one on abdominal segment 6/7, one on 7/8.
• Male:   
  
• Phallosome has long external parameres, extending beyond tip.
• Phallosome tip is sclerified.
• Hypandrium is simple.
• Female: 
  
• Subgenital plate has double posterior lobe, without distal extension.
• Gonapophyses complete and well developed:
• Ventral valve slender and pointed.
• Dorsal valve has a rounded lobe that tapers to a point.
• External valve is broad, round, and hairy.
• Eggs:  Eggs are covered by an encrustation of debris.

How to Know the Family

• Delicate-looking slender bark lice, 2-2.5 mm in length.
• Yellow in color with faint spotting on wings.
• Tarsi have 2 segments.
• Abdomen has a single abdominal vesicle in adults, two in nymphs.
• Forewings with abundant hairs; hairs on margin do not cross each other.
• Hindwing veins Rs, M, and Cu are not fused at base.

Family Monophyly

Monophyly of the family Trichopsocidae is supported by the secondary loss of the distal extension of the subgenital plate in the female (Yoshizawa 2002). The morphological variation within this small family is not well known.

Discussion of Phylogenetic Relationships

Relationships within the family have not been investigated using molecular techniques.

Other Names for Trichopsocus

• Trichopsocidae

References

Johnson, K. P. & E. L. Mockford. 2003. Molecular Systematics of Psocomorpha (Psocoptera). Systematic Entomology 28: 409-40

Lienhard, C. and C. N Smithers. 2002. Psocoptera (Insecta) World Catalogue and Bibliography. Muséum d'Histoire Naturelle, Geneva, Switzerland.

Mockford, E. L. 1993. North American Psocoptera (Insecta). Gainesville, Florida: Sandhill Crane Press,

New, T.R. 2005. Psocids, Psocoptera (Booklice and barklice), 2nd edition: Handbooks for the Identification of British Insects. Vol. 1, Part 7. Royal Entomological Society, London, UK.

Smithers, C. N. 1996. Psocoptera. Pp. 1-80, 363-372 (Index) in Wells A. (ed.) Zoological Catalogue of Australia. Vol. 26. Psocoptera, Phthiraptera, Thysanoptera. Melbourne: CSIRO Publishing, Australia.

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