Psilopsocus

Introduction

The family Psilopsocidae contains one genus, Psilopsocus, with 7 species.  They are found only in Southeast Asia and Australia.

Psilopsocids are medium to large-sized bark lice (3.5-4.5 mm).  Adults live on the surface of bark and nymphs bore into wood.  These are the only known wood boring psocids.

Characteristics

Synapomorphies

• Wood boring behavior of nymphs.
• Forewing areola postica is always separate from the M vein.
• Male: phallosome has rounded apex.
  

General Characters

• Head: Antennae have 13 segments.
• Leg: Tarsi have 3 segments.
  
• Wings:
• Forewing is elongated.
• Forewing are hairless on surface and margins.
• Forewing veins have "Caecillius" pattern:
• Areola postica is free of vein M.
• Veins Rs and M are usually fused for part of their length.
• Veins CuA1 and CuA2 divide more anterior to wing margin than in other families.
• Male:  Phallosome is simple closed ring, rounded at apex,  with light sclerification at tip.
• Female: 
  
• Gonapophyses are complete:
• Ventral valve is long and pointed.
• Dorsal valve is long and pointed.
• External valve is very broad and hairy.
• Eggs:   Eggs are laid singly and are heavily encrusted with debris.

How to Know the Family

• Nymphs with hind region of abdomen heavily sclerotised.
• Antennae are 1.5 times length of body.
• Forewings are hairless.
• Forewing areola postica is free of vein M.
• Hindwings are hairless.

Discussion of Phylogenetic Relationships

There has been no phylogenetic analysis of relationships within the family Psilopsocidae. 

The relationship of Psilopsocidae and other families of Psocetae is not well understood.  It was long assumed that Psilopsocidae is most closely related to Myopsocidae (Mockford 1961), but recent analyses bring this relationship into question.  In two studies of Psocomorpha that each included only one species of Psilopsocus, the family was found to be sister to Hemipsocidae with molecular data (18S rDNA; Johnson et al. 2004), and was placed as sister to Psocidae in morphological analysis (Yoshizawa 2002).  Psilopsocidae continues to be considered "one of the least known and most controversial families" within Psocomorpha (Yoshizawa 2002).

Other Names for Psilopsocus

• Psilopsocidae

References

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.

Mockford EL. 1961. The rediscovery and probable phylogenetic position of Psilopsocus (Psocoptera). Psyche 68: 38-44.

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

New, T.R. and S.S. Leed. 1984. A new species of Psilopsocus Enderlein (Psocoptera: Psilopsocidae) from Malaysia. Journal of the Australian Journal of Entomology 30: 63-65.

Smithers, C.N. 1963. Psilopsocus mimulus sp.n. (Psocoptera: Psilopsocidae), representing a family new to Australia. Journal of the Entomological Society of Queensland 2: 56-59.

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.