Psocodea

Key takeaways

Psocodea belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Psocodea to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Psocodea from memory before moving on to harder problems.

Reference excerpt

Psocodea is a taxonomic group of insects comprising the bark lice, book lice and parasitic lice. It was formerly considered a superorder, but is now generally considered by entomologists as an order. Despite the greatly differing appearance of parasitic lice (Phthiraptera), they are believed to have evolved from within the former order Psocoptera, which contained the bark lice and book lice, now found to be paraphyletic. Psocodea contains around 11,000 species, divided among three suborders and more than 70 families. They range in size from 1–10 millimetres (0.04–0.4 in) in length. The species known as booklice received their common name because they are commonly found amongst old books—they feed upon the paste used in binding. The barklice are found on trees, feeding on algae and lichen.

External phylogeny Psocodea has been recovered as a monophyletic group in recent studies. Their next closest relatives are traditionally recognized as the monophyletic grouping Condylognatha that contains Hemiptera (true bugs) and Thysanoptera (thrips), which all combined form the group Paraneoptera. However, this is somewhat unclear, as analysis has shown that Psocodea could instead be the sister taxon to Holometabola, which would render Paraneoptera as paraphyletic. Here is a simple cladogram showing the traditional relationships with a monophyletic Paraneoptera:

Here is an alternative cladogram showing Paraneoptera as paraphyletic, with Psocodea as sister taxon to Holometabola:

Internal phylogeny Here is a cladogram showing the relationships within Psocodea:

Classification The order Psocodea (formerly 'Psocoptera') is divided into three extant suborders.

Suborder Trogiomorpha Trogiomorpha have antennae with many segments (22–50 antennomeres) and always three-segmented tarsi. Trogiomorpha is the smallest suborder of the Psocoptera sensu stricto (i.e., excluding Phthiraptera), with about 340 species in 7 families, ranging from the fossil family Archaeatropidae with only a handful of species to the speciose Lepidopsocidae (over 200 species). Trogiomorpha comprises infraorder Atropetae (extant families Lepidopsocidae, Psoquillidae and Trogiidae, and fossil families Archaeatropidae and Empheriidae) and infraorder Psocathropetae (families Psyllipsocidae and Prionoglarididae).

Suborder Troctomorpha Troctomorpha have antennae with 15–17 segments and two-segmented tarsi. Troctomorpha comprises the Infraorder Amphientometae (families Amphientomidae, Compsocidae, Electrentomidae, Musapsocidae, Protroctopsocidae and Troctopsocidae) and Infraorder Nanopsocetae (families Liposcelididae, Pachytroctidae and Sphaeropsocidae). Troctomorpha are now known to also contain the order Phthiraptera (lice), and are therefore paraphyletic, as are Psocoptera as a whole. Some Troctomorpha, such as Liposcelis (which are similar to lice in morphology), are often found in birds' nests, and it is possible that a similar behavior in the ancestors of lice is at the origin of the parasitism seen today.

Suborder Psocomorpha Psocomorpha are notable for having antennae with 13 segments. They have two- or three-segmented tarsi, this condition being constant (e.g., Psocidae) or variable (e.g., Pseudocaeciliidae) within families. Their wing venation is variable, the most common type being that found in the genus Caecilius (rounded, free areola postica, thickened, free pterostigma, r+s two-branched, m three-branched). Additional veins are found in some families and genera (Dicropsocus and Goja in Epipsocidae, many Calopsocidae, etc.) Psocomorpha is the largest suborder of the Psocoptera sensu stricto (i.e., excluding Phthiraptera), with about 3,600 species in 24 families, ranging from the species-poor Bryopsocidae (2 spp.) to the speciose Psocidae (about 900 spp). Psocomorpha comprises Infraorder Epipsocetae (families Cladiopsocidae, Dolabellopsocidae, Epipsocidae, Neurostigmatidae and Ptiloneuridae), Infraorder Caeciliusetae (families Amphipsocidae, Asiopsocidae, Caeciliusidae, Dasydemellidae and Stenopsocidae), Infraorder Homilopsocidea (families Archipsocidae, Bryopsocidae, Calopsocidae, Ectopsocidae, Elipsocidae, Lachesillidae, Mesopsocidae, Peripsocidae, Philotarsidae, Pseudocaeciliidae and Trichopsocidae) and Infraorder Psocetae (families Hemipsocidae, Myopsocidae, Psilopsocidae and Psocidae).

References

External links

National Barkfly Recording Scheme Psoco Net Tree of Life: Psocodea Archipsocus nomas, a webbing barklouse on the UF / IFAS Featured Creatures Web site

Illustrations

Worked examples

Example 1 — a first encounter with Psocodea

Start with the simplest possible case. Write down what Psocodea claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Psocodea before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Psocodea ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Psocodea

In research: Psocodea appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Psocodea in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Psocodea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Insect orders, Paraneoptera, Psocodea, so understanding it makes those chapters shorter.
In everyday life: Look for Psocodea outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Psocodea in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Psocodea means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Psocodea out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Psocodea in simple terms?

Psocodea is a taxonomic group of insects comprising the bark lice, book lice and parasitic lice. It was formerly considered a superorder, but is now generally considered by entomologists as an order.

Why does Psocodea matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Psocodea?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Psocodea.