Belongs within: Nanopsocetae.
Liposcelis, the booklice, is a cosmopolitan genus of minute flattened, wingless insects with a number of species being widely synanthropic. The genus is readily distinguised from related forms by the presence of a lateral protuberance on the hind femur (Mockford 1993).
Liposcelis has been divided into a number of sections and groups on the basis of diagnostic features though the evolutionary significance of these groups remains undetermined. Members of section II possess a clearer band of integument across the rear of the third and fourth abdominal tergites, giving the abdomen a banded appearance, and may possess bristles on the posterior half of the prosternum, whereas members of section I lack such abdominal bands and only have bristles on the anterior of the prosternum. Within section I, members of group A have a transverse row of up to five bristles on the lateral pronotal lobes whereas there are no such bristles in group B. Within section II, group C is characterised by having all prosternal setae in front of the middle of the sternum whereas group D have a pair of lateral setae behind the middle of the prosternum (Mockford 1993).
Within group I-A, Liposcelis brunnea is a synanthropic species with a single supplementary long bristle on each lateral lobe of the pronotum (Mockford 1993).
Booklice: the cutest of pests
Published 26 April 2013
Humans have a tendency to think of ‘nature’ and the ‘environment’ as something distinct from our own society. Environments unmodified by humans are seen as ‘natural’ whereas structures created by human activity, such as buildings, are not ‘natural’ and thought to be somehow outside the ‘environment’. As such, people often react strongly to the idea of things associated with the ‘environment’, such as non-human wildlife, encroaching on their homes. But of course, human houses are as much an environment of their own as any other of the world’s habitats, and many animals find them to be places where they can thrive. Among the animals that most regularly share our houses with us are booklice of the genus Liposcelis.
Representatives of Liposcelis can be found almost anywhere in the world except in the coldest of regions. About 130 species have been described in the genus to date (Yoshizawa & Lienhard 2010) with doubtless more yet to be discovered (by comparison, Broadhead’s review of the genus in 1950 recognised only 22 species, with a six-fold increase since then). The family Liposcelididae, to which Liposcelis belongs, differ from other free-living members of the Psocodea (or ‘Psocoptera’) in their flattened body form, as well as being smaller than most other examples (Liposcelis grow little more than a millimetre in length). In the flattened habitus, they resemble the parasitic true lice of the Phthiraptera, and recent studies have agreed that the liposcelidids represent the closest relatives of true lice (Yoshizawa & Lienhard 2010). Liposcelis species are readily distinguished from other liposcelidids by the shape of the hind legs: an obtuse tubercle on the outer margin of the hind femur gives it a distinctly broad appearance* (indeed, the genus name Liposcelis translates into English as ‘fat thigh’). Liposcelis are also distinctive in being invariably wingless; other liposcelidid species typically come in both winged and wingless forms. Though the genus as a whole is easily recognised, distinguishing individual species is often a far more challenging prospect requiring microscopic examination of fine features of the chaetotaxy (arrangement of bristles on the body) and cuticular sculpture. Authors have divided Liposcelis species between a number of diagnostic sections and subgroups based on these and other features but the monophyly or otherwise of these subdivisions is largely unstudied.
*This feature is also shared with a cave-dwelling species from Ascension Island currently placed in its own genus, Troglotroctes ashmoleorum, but it seems more than likely that this species is itself a derived offshoot of Liposcelis.
Liposcelis species can feed on a wide range of organic matter but, like other ‘Psocoptera’, their primary source of food is probably yeasts and fungal spores (their vernacular name has been attributed to their feeding on yeasts growing on the glue binding books, though I would note that they are also probably more likely to be seen crawling on the light background of a book’s page than in other, less closely examined corners of the house). Turner (1994) provided a detailed review of the natural history of one of the most widespread domestic pest species in the genus, L. bostrychophila, and reports that he was able to maintain cultures on “‘Weetabix’™, ‘Shreddies’™, baby rice, soya granules, sage and onion stuffing mix, skimmed milk powder, ‘Oat Krunchies’™, red lentils, and yellow split peas“. Other stored foods from which complaints had been received of booklice included “sugar, bread, salt, bay leaves, gelatine powder, poppadoms, custard powder, dried yeast, instant potato, nuts, dried fruit, baby food, sauce mix, dried mushrooms, pasta, coconut, cocoa, milk powder, spices, glace cherries, garlic, baking powder, icecream mix, dried soup, cracked wheat, carob powder, maize meal, wheat germ, jellied sweets and bread crumbs“. They have also been found on cured meat and may damage curated insect specimens. As well as obtaining moisture from their food, Liposcelis are also able to extract water directly from the atmosphere owing to the hygroscopic properties of their saliva. A booklouse will hold a drop of saliva inside its mouth, then swallow it when the ball has absorved enough water from the air.
Female Liposcelis bostrychophila generally reach maturity and begin producing eggs about two weeks after hatching and may produce two or three eggs a day. As each egg is about one-third the size of the adult, this means that a female at peak fecundity is producing her own body mass in eggs in a single day. Most Liposcelis species reproduce sexually but some are parthenogenetic. Domestic L. bostrychophila, for instance, seem to be entirely parthenogenetic with males of the species only known from isolated collections in Hawaii, Arizona and Senegal (Georgiev et al. 2020). Studies on an unnamed species of Liposcelis from Arizona found that sex determination seemed to be facultative, determined by the mother, with no evidence for differentiated sex chromosomes (Hodson et al. 2017). Females seemed to produce more males early in life and more females later. The same studies also established the occurrence of paternal genome elimination in this species, where chromosomes inherited from the father were inactivated in the offspring and not passed on to their own progeny (which raises the question that, if males are effectively a genetic dead end, why would a female produce male offspring at all?) Paternal genome elimination has also been found in the human louse Pediculus humanus, and may be characteristic of the broader clade encompassing these species, but other species remain unstudied. Liposcelis genomes are also remarkable in the occurrence of fragmentation of the mitochondrial genome. Whereas some Liposcelis species have only a single mitochondrial chromosome, as is standard for most other animals, some species have the mitochondrial genome divided between two, three, five or seven chromosomes (Feng et al. 2019). The functional significance, if any, of this feature remains unknown.
Though booklice may be found in houses and stores on the regular, they are mostly only minor pests, only causing distress when reaching large numbers (an exceptional case quoted by Turner, 1994, involved a house in New Jersey at the beginning of the 1900s that became so infested “‘that a pinpoint could not have been put down without touching one or more of these bugs“). They are not believed to transmit pathogens, except perhaps incidentally by carrying microbes from one store to another. For the most part, these little beasties are just another part of the wildlife that shares our homes with us, whether we are aware of them or not.
Systematics of Liposcelis
Characters (from Mockford 1993): Apterous. Hind femur with lateral protuberance. Pretarsal claw without basal seta. Subgenital plate with t-shaped sclerite.
<==Liposcelis Motschulsky 1852YL10
|--Section IYL10
| |--Group I-AMK08
| | | i. s.: L. abdominalis Badonnel 1962B62
| | | L. albothoracica Broadhead 1955 [=L. albothoracicus]L98
| | | L. antennatoides Li & Li 1995L02
| | | L. badia Wang, Wang & Lienhard 2006WWL06
| | | L. canariensis Lienhard 1996L98
| | | L. cibaritica Li & Li 2002WWL06, YL10
| | | L. delamarei Badonnel 1962B62
| | | L. discalis Badonnel 1962B62
| | | L. jilinica Li & Li 2002WWL06, YL10
| | | L. laoshanensis Li & Li 2002WWL06, YL10
| | | L. naturalis Li & Li 2002WWL06, YL10 [=L. natiuralisL03]
| | | L. nigritibia Li & Li 1995L02
| | | L. nigrocincta Badonnel 1962B62, YL10
| | | L. palatina Roesler 1954 [=L. palatinus]L98
| | | L. reticulata Badonnel 1962B62, YL10
| | | L. rufiornata Li & Li 1995L02
| | | L. sinica Li & Li 1995L02
| | | L. yunnaniensis Li & Li 1995L02
| | |--Group I-AaM93
| | | |--*L. brunnea Motschulsky 1852M93 [=L. brunneusL98; incl. L. liparus Broadhead 1947L02]
| | | |--L. liparoides Badonnel 1962M93, YL10
| | | `--L. setosa Badonnel 1963M93, YL10
| | |--Group I-AbMK08
| | | |--L. castrii Badonnel 1963B86, YL10
| | | |--L. dentata Badonnel 1986B86, YL10 [=L. dentatusB86]
| | | |--L. entomophila (Enderlein 1907)M93 (see below for synonymy)
| | | |--L. fusciceps Badonnel 1968M93
| | | |--L. hirsuta Badonnel 1948M93, YL10 [=L. hirsutusB50]
| | | |--L. hirsutoides Mockford 1978M93
| | | |--L. marginepunctata Badonnel 1969M93, YL10
| | | |--L. ornata Mockford 1978 [=L. ornatus]M93
| | | |--L. pallens Badonnel 1968M93
| | | |--L. pallida Mockford 1978MK08 [=L. pallidusM93]
| | | |--L. villosa Mockford 1971MK08 [=L. villosusM93]
| | | `--+--L. deltachi Sommerman 1957MK08
| | | |--L. nasus Sommerman 1957MK08
| | | |--L. maunakea Mockford & Krushelnycky 2008MK08
| | | `--L. volcanorum Mockford & Krushelnycky 2008MK08
| | `--Group I-AcB86
| | |--L. alticolis Badonnel 1986B86
| | | |--L. a. alticolisB86
| | | `--L. a. cumbalensis Badonnel 1986B86
| | |--L. chilensis Badonnel 1963B86, YL10
| | `--L. mimula Badonnel 1986B86, YL10 [=L. mimulusB86]
| `--Group I-BMK08
| |--L. bicolor (Banks 1900) [=Troctes bicolor]L98
| |--L. bouilloni Badonnel 1974L02
| |--L. decolor (Pearman 1925) (see below for synonymy)L02
| |--L. keleri Günther 1974 [incl. L. sculptilis Lienhard 1977]L98
| |--L. kyrosensis Badonnel 1971L98
| |--L. lacinia Sommerman 1957M93
| |--L. maculata Lienhard 1996L98
| |--L. meridionalis (von Rosen 1911) [=Troctes meridionalis; incl. T. gallicus Pearman 1951, Liposcelis gallicus]L98
| |--L. myrmecophila Broadhead 1950 [=L. myrmecophilus]L98
| |--L. nigra (Banks 1900) [=Troctes niger; incl. L. knullei Broadhead 1971]M93
| |--L. orghidani Badonnel 1973 [incl. L. orghidani atratus Badonnel 1973]L98
| |--L. pearmani Lienhard 1990YL10
| |--L. picta Ball 1940 [=L. pictus]L98
| |--L. priesneri Enderlein 1925 [incl. L. montanum Badonnel 1971]L98
| |--L. pulchra Lienhard 1980 [=L. pulcher]L98
| |--L. purpurea (Aaron 1883) (n. d.)M93, YL10 [=Atropos purpureaM93, Troctes purpureaB50]
| |--L. rufa Broadhead 1950 [=L. rufus]MK08
| |--L. silvarum (Kolbe 1888) [=Troctes silvarum]L98
| |--L. triocellata Mockford 1971 [=L. triocellatus]M93
| `--L. uxoris Lienhard 1980L98
`--Section IIYL10
|--Group II-CMK08
| |--L. australis Smithers 1996S96
| |--L. ayosae Lienhard 1996MK08
| |--L. barrai Badonnel 1969MK08
| |--L. bicoloripes Badonnel 1955S96, B55
| |--L. bogotana Badonnel 1986MK08
| |--L. elegantis Li & Li 1995L02
| |--L. exigua Badonnel 1931MK08 [=L. exiguusB50]
| | |--L. e. exiguaB86
| | `--L. e. oligopsB86
| |--L. fallax Badonnel 1986B86
| |--L. formicaria (Hagen 1865)L98 [=Atropos formicariaL98, L. formicariusL98, Troctes formicariusM93]
| |--L. kipukae Mockford & Krushelnycky 2008MK08
| |--L. lenkoi Badonnel 1968S96, YL10
| |--L. lunae Badonnel 1969MK08
| |--L. mendax Pearman 1946L02
| |--L. mira Badonnel 1986MK08
| |--L. montamargensis Badonnel 1967S96, YL10
| |--L. obscura Broadhead 1954MK08 [=L. obscurusL98]
| |--L. pacifica Badonnel 1986MK08
| |--L. paetula Broadhead 1950MK08 [=L. paetulusB50]
| |--L. parvula Badonnel 1963MK08
| |--L. pauliani Badonnel 1967S96, YL10
| |--L. pubescens Broadhead 1947L98
| |--L. romeralensis Badonnel 1967MK08
| |--L. tamminensis Smithers 1996S96
| `--L. tetrops Badonnel 1986MK08
`--Group II-DMK08
|--L. aconae Badonnel 1974L98
|--L. arenicola Günther 1974 [=L. arenicolus]L98
|--L. bostrychophila Badonnel 1931MK08 (see below for synonymy)
|--L. capitisecta Wang, Wang & Lienhard 2006WWL06
|--L. compacta Lienhard 1990L98
|--L. corrodens (Heymons 1909) [=Troctes corrodens; incl. L. subfuscus Broadhead 1947]L98
|--L. edaphica Lienhard 1990L02
|--L. flavida Badonnel 1969M74, YL10
|--L. nuptialis Badonnel 1972M93, YL10
|--L. paeta Pearman 1942 [=L. paetus]L02
|--L. prenolepidis (Enderlein 1909) [=Troctes prenolepidis]M93
|--L. rugosa Badonnel 1945 [=L. rugosus]L98
|--L. sculptilimacula Li & Li 1995WWL06, YL10 (see below for synonymy)
|--L. semicaeca Lienhard 1990L98
|--L. tricolor Badonnel 1973L98
`--L. yangi Li & Li 1998L02
Liposcelis incertae sedis:
L. ambigua Badonnel 1972YL10
L. angolensis Badonnel 1955YL10
|--L. a. angolensisB55
`--L. a. areolatus Badonnel 1955B55
L. annulata Badonnel 1955YL10
L. anomala Badonnel 1955YL10
L. atavus Enderlein 1911YL10
L. bengalensis Badonnel 1981YL10
L. borbonensis Badonnel 1977YL10
L. broadheadi Badonnel 1969YL10
L. desertica Badonnel 1955YL10
L. dichromis Badonnel 1967YL10
L. distincta Badonnel 1955YL10
L. divinatoria (Müller 1776) (n. d.)MK08 [=Termes divinatoriumG74, L. divinatoriumNL07, L. divinatoriusMK08]
L. fasciata (Enderlein 1908)YL10 [=Troctes fasciatusB50]
L. globiceps Badonnel 1967YL10
L. guentheri Badonnel 1982YL10
L. kidderi (Hagen 1883)YL10 [=Atropos divinatoria var. kidderiL02, Troctes kidderiL02]
L. laparvensis Badonnel 1967YL10
L. machadoi Badonnel 1969YL10
L. maracayensis Mockford 1996YL10
L. minuta Badonnel 1974YL10
L. nigrofasciata Badonnel 1963YL10
L. perforata Badonnel 1955YL10
L. plesiopuber Broadhead & Richards 1982YL10
L. puber Badonnel 1955YL10
L. resinata (Hagen 1865)YL10 [=Atropos resinataNPA04, L. resinatusB50]
L. similis Badonnel 1972YL10
L. transvaalensis (Enderlein 1909)YL10 [=Troctes transvaalensisB50]
L. varians Badonnel 1955B55
Nomen nudum: Liposcelis museorum Motschulsky 1853B50
Liposcelis bostrychophila Badonnel 1931MK08 [=L. bostrychophilusMK08; incl. L. divergens Badonnel 1943L02, L. granicola Broadhead & Hobby 1944L02, L. bostrichophilus granulosus Badonnel 1962G74]
Liposcelis decolor (Pearman 1925) [=Troctes bicolor var. decolor; incl. L. luridus Broadhead 1947, L. macedonicus Günther 1980, L. terricolis monnictae Badonnel 1971, L. silvarum palpalis Badonnel 1971, L. simulans Broadhead 1950, L. terricolis Badonnel 1945]L02
Liposcelis entomophila (Enderlein 1907)M93 [=Troctes entomophilusL02, L. entomophilusL02; incl. L. bakeri Pearman 1928L02, L. virgulatus Pearman 1929L02]
Liposcelis sculptilimacula Li & Li 1995WWL06, YL10 [=L. sculptilis (l. c.) non Lienhard 1977WWL06, L. sculptimacula (l. c.)WWL06]
*Type species of generic name indicated
References
[B55] Badonnel, A. 1955. Psocoptères de l’Angola. Diamang Publicações Culturais 26: 11–267.
[B62] Badonnel, A. 1962. Psocoptères. In: Biologie de l’Amerique Australe vol. 1. Études sur la faune du sol pp. 185-229. Eds. Centre Nat. Recherche Sci.: Paris.
[B86] Badonnel, A. 1986. Psocoptères de Colombie (Insecta, Psocoptera). Spixiana 9 (2): 179–223.
[B50] Broadhead, E. 1950. A revision of the genus Liposcelis Motschulsky with notes on the position of this genus in the order Corrodentia and on the variability of ten Liposcelis species. Transactions of the Royal Entomological Society of London 101 (10): 335–388, pls 1–3.
Feng, S., H. Li, F. Song, Y. Wang, V. Stejskal, W. Cai & Z. Li. 2019. A novel mitochondrial genome fragmentation pattern in Liposcelis brunnea, the type species of the genus Liposcelis (Psocodea: Liposcelididae). International Journal of Biological Macromolecules 132: 1296–1303.
Georgiev, D., A. Ostrovsky & C. Lienhard. 2020. A new species of Liposcelis (Insecta: Psocoptera: Liposcelididae) from Belarus. Ecologica Montenegrina 29: 41–46.
[G74] Günther, K. K. 1974. Staubläuse, Psocoptera. Die Tierwelt Deutschlands 61: 1–315.
Hodson, C. N., P. T. Hamilton, D. Dilworth, C. J. Nelson, C. I. Curtis & S. J. Perlman. 2017. Paternal genome elimination in Liposcelis booklice (Insecta: Psocodea). Genetics 206: 1091–1100.
[L02] Li F. 2002. Psocoptera of China vol. 1. Science Press: Beijing.
[L98] Lienhard, C. 1998. Faune de France. France et Régions Limitrophes. 83. Psocoptères Euro-Méditerranéens. Fédération Française des Sociétés de Sciences Naturelles: Paris.
[L03] Lienhard, C. 2003. Nomenclatural amendments concerning Chinese Psocoptera (Insecta), with remarks on species richness. Revue Suisse de Zoologie 110 (4): 695–721.
[M74] Mockford, E. L. 1974. Records and descriptions of Cuban Psocoptera. Entomologica Americana 48 (2): 103–215.
[M93] Mockford, E. L. 1993. North American Psocoptera (Insecta). Sandhill Crane Press, Inc.
[MK08] Mockford, E. L., & P. D. Krushelnycky. 2008. New species and records of Liposcelis Motschulsky (Psocoptera: Liposcelididae) from Hawaii with first description of the male of Liposcelis bostrychophila Badonnel. Zootaxa 1766: 53–68.
[NPA04] Nel, A., G. De Ploëg & D. Azar. 2004. The oldest Liposcelididae in the lowermost Eocene amber of the Paris Basin (Insecta: Psocoptera). Geologica Acta 2 (1): 31–36.
[NL07] New, T. R., & C. Lienhard. 2007. The Psocoptera of Tropical South-east Asia. Brill: Leiden.
[S96] Smithers, C. N. 1996. Psocoptera from the Western Australian wheatbelt. Gen. Appl. Ent. 27: 13–18.
Turner, B. D. 1994. Liposcelis bostrychophila (Psocoptera: Liposcelididae), a stored food pest in the UK. International Journal of Pest Management 40 (2): 179–190.
[WWL06] Wang Z.-Y., Wang J.-J. & C. Lienhard. 2006. Two new species of Liposcelis (Psocoptera, Liposcelididae) from China. Acta Zootaxonomica Sinica 31 (3): 564–568.
[YL10] Yoshizawa, K., & C. Lienhard. 2010. In search of the sister group of the true lice: a systematic review of booklice and their relatives, with an updated checklist of Liposcelididae (Insecta: Psocodea). Arthropod Systematics and Phylogeny 68 (2): 181–195.