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Emilie Bess and Kevin P. Johnson
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Containing group: Homilopsocidea


The family Mesopsocidae contains about 74 species in 12 genera distributed worldwide, with highest diversity in tropical Africa and Eurasia.  Three species are known from North America in the genus Mesopsocus.

Mesopsocids are medium-to-large sized bark lice (3-4.5 mm, nymphs up to 4 mm). Sexual dimorphism is common in this family: males are slender and winged, females are stout with short wings or wingless, and much larger than the males.  Mesopsocids inhabit bark and stone surfaces, and one species has been associated with termite nests.



Epistomal suture of head had a broad internal ridge.
Forewing suface lacks hairs on margins, veins, and membrane.
Female: ventral valve of gonapophyses is broad apically and pointed.

General Characters

How to Know the Family

Family Monophyly

Family monophyly is supported by three unique characters: wing surface lacking hairs, the epistomal suture on the head with a broad internal ridge, and, on the female genitalia, the ventral valve of the gonapophyses apically broadened (Yoshizawa 2002).  Molecular phylogenetic study has supported the monophyly of two species of Mesopsocus, but monophyly of the family with respect to genus Idatenopsocus was unclear (Johnson et al. 2004).

Discussion of Phylogenetic Relationships

Relationships within the family Mesopsocidae have not been studied in detail.  Mesopsocidae has traditionally been included in superfamily Homilopsocidea and this placement of genus Mesopsocus is supported by molecular data (18S nDNA, Johnson et al. 2004).  Morphological data support a sister relationship between Mesopsocidae and Philotarsidae, based on two characters: the hindwing margin with hairs between veins R2+3 and R 4+5 only, and, in the male, a rounded apex of the phallosome (present in some Mesopsocidae and considered the “ground plan” for the family) (Badonnel and Leinhard 1988, Yoshizawa 2002).


Badonnel A, Lienhard C. 1988. Révision de la famille des Mesopsocidae (Insecta: Psocoptera). Bulletin du Muséum national d’Histoire naturelle 4, 2: 375–412.

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

Johnson, K. P., K. Yoshizawa, and V. S. Smith. 2004. Multiple origins of parasitism in lice. Proceedings of the Royal Society of London B 271:1771-1776.

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

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.

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

Mockford, E. L. 2007. Species of Philotarsus from north and middle America and a new Philotarsine genus from Mexico, Guatemala, and the Greater Antilles (Psocoptera: Philotarsidae: Philotarsinae). Journal of the New York Entomological Society 114: 108-139.

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.

Title Illustrations
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Scientific Name Mesopsocus unipunctatus
Specimen Condition Live Specimen
Identified By K. Yoshizawa
Sex Female
Life Cycle Stage micropterous adult
View anterolateral
Size 3mm
Copyright © 2006 Kazunori Yoshizawa
Scientific Name Mesopsocus unipunctatus
Specimen Condition Live Specimen
Identified By K. Yoshizawa
Life Cycle Stage adult
View lateral
Size 4mm
Copyright © 2006 Kazunori Yoshizawa
About This Page

Emilie Bess
Illinois Natural History Survey, Champaign, Illinois, USA

Kevin P. Johnson
Illinois Natural History Survey, Champaign, Illinois, USA

Correspondence regarding this page should be directed to Emilie Bess at and Kevin P. Johnson at

All Rights Reserved.

Citing this page:

Bess, Emilie and Kevin P. Johnson. 2009. Mesopsocidae. Version 25 March 2009 (under construction). http://tolweb.org/Mesopsocidae/14480/2009.03.25 in The Tree of Life Web Project, http://tolweb.org/

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