403
lice principally infest birds, but one-eighth of the species represent three nonspeciose, minor families that are on mammals (Galloway 2018). The next derived (and
most diverse) clade is Ischnocera, the chewing lice 2 clade, representing 54% of
phthirapteran species. Ischnocera primarily parasitize birds, although, as in the
Amblycera, about one-eighth is on mammalian hosts. The Amblycera and Ischnocera
are characterized by mandibulate mouthparts, broad and flattened heads, and typically consume flaked off skin, integumental exudates such as sebum and sweat,
other debris such as fungi associated with feathers and occasionally blood and
lymph at the skin surface (Lehane 1991). The major structural differences between
these two major types of chewing lice involve their heads and mouthparts. The third
clade, Rhyncophthirina, has highly modified chewing mouthparts that have been
reduced to tiny pincer-like mandibles at the end of a long tubular extension of the
head capsule for imbibing of blood and dermal secretions, akin to piercing and
sucking. Rhyncophthirina is a highly specialized, blood-feeding clade that occurs
only on mammals and consists of one genus and three species that parasitize the
African elephant, wart hog and Red River hog as hosts (Galloway 2018).
Sister-group to the Rhyncophthirina is the Anoplura, the sucking lice, which are
the only truly piercing-and-sucking clade with stylate mouthparts within
Phthiraptera. Anoplura secure their food by targeting blood vessels and attach their
eggs, known as nits, to the hair of their hosts by large, grasping and curved tarsal
claws (Fig. 11.1k). Anoplura parasitize most orders of placental mammals by feeding on their blood. About 70% are associated with rodents (Light et al. 2010), but
are not found on armadillos, pangolins, elephants, aquatic species except for seals,
and are notably absent on bats (Durden and Musser 1994). Based on a phylogenetic
analysis of Anoplura (Light et al. 2010), the clade originated during the Late
Cretaceous (Campanian Stage) around 77 million years ago, but did not diversify
until the early Paleogene, after the ecologic crisis marking the Cretaceous–Paleogene
boundary, and presumably coincident with the diversification of many warmblooded mammal lineages. A notable exception to anopluran and other phthirapteran hosts are bats, which are inferred to be present and diverse during the Paleogene
diversification of placental mammals (Teeling et al. 2005). Phthirapteran absence
from bat hosts may be attributable to competition from their previously acquired,
rich fauna of parasites that included mites, bat bugs, bat flies and fleas, or were limited by the significant drops in bat body temperatures during hibernation (Grimaldi
and Engel 2015a). Both limitations would eliminate phthirapterans as hosts (Clayton
et al. 2016).
Phthiraptera have a poor, but rather remarkable fossil record. The oldest yet most
bizarre specimen is a large, 17 mm long Saurodectes vrsanskyi (Fig. 11.1h) of the
monotypic Saurodectidae from the Early Cretaceous (130 Ma) Baissa locality in
Transbaikalia, Russia (Rasnitsyn and Zherikhin 1999). This specimen bears several
anomalous features: a large size of 17 mm in length; well-developed, compound eyes;
a pair of peculiar, horn-like appendages extending laterally from each side of the head;
long and ambulatory legs; widely separated leg bases; a pair of robust spines behind
the forecoxae; and exceptionally small claws. These characters are atypical compared
to modern species of Phthiraptera. The initial, reasonable, attribution of the
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
lice principally infest birds, but one-eighth of the species represent three nonspeciose, minor families that are on mammals (Galloway 2018). The next derived (and
most diverse) clade is Ischnocera, the chewing lice 2 clade, representing 54% of
phthirapteran species. Ischnocera primarily parasitize birds, although, as in the
Amblycera, about one-eighth is on mammalian hosts. The Amblycera and Ischnocera
are characterized by mandibulate mouthparts, broad and flattened heads, and typically consume flaked off skin, integumental exudates such as sebum and sweat,
other debris such as fungi associated with feathers and occasionally blood and
lymph at the skin surface (Lehane 1991). The major structural differences between
these two major types of chewing lice involve their heads and mouthparts. The third
clade, Rhyncophthirina, has highly modified chewing mouthparts that have been
reduced to tiny pincer-like mandibles at the end of a long tubular extension of the
head capsule for imbibing of blood and dermal secretions, akin to piercing and
sucking. Rhyncophthirina is a highly specialized, blood-feeding clade that occurs
only on mammals and consists of one genus and three species that parasitize the
African elephant, wart hog and Red River hog as hosts (Galloway 2018).
Sister-group to the Rhyncophthirina is the Anoplura, the sucking lice, which are
the only truly piercing-and-sucking clade with stylate mouthparts within
Phthiraptera. Anoplura secure their food by targeting blood vessels and attach their
eggs, known as nits, to the hair of their hosts by large, grasping and curved tarsal
claws (Fig. 11.1k). Anoplura parasitize most orders of placental mammals by feeding on their blood. About 70% are associated with rodents (Light et al. 2010), but
are not found on armadillos, pangolins, elephants, aquatic species except for seals,
and are notably absent on bats (Durden and Musser 1994). Based on a phylogenetic
analysis of Anoplura (Light et al. 2010), the clade originated during the Late
Cretaceous (Campanian Stage) around 77 million years ago, but did not diversify
until the early Paleogene, after the ecologic crisis marking the Cretaceous–Paleogene
boundary, and presumably coincident with the diversification of many warmblooded mammal lineages. A notable exception to anopluran and other phthirapteran hosts are bats, which are inferred to be present and diverse during the Paleogene
diversification of placental mammals (Teeling et al. 2005). Phthirapteran absence
from bat hosts may be attributable to competition from their previously acquired,
rich fauna of parasites that included mites, bat bugs, bat flies and fleas, or were limited by the significant drops in bat body temperatures during hibernation (Grimaldi
and Engel 2015a). Both limitations would eliminate phthirapterans as hosts (Clayton
et al. 2016).
Phthiraptera have a poor, but rather remarkable fossil record. The oldest yet most
bizarre specimen is a large, 17 mm long Saurodectes vrsanskyi (Fig. 11.1h) of the
monotypic Saurodectidae from the Early Cretaceous (130 Ma) Baissa locality in
Transbaikalia, Russia (Rasnitsyn and Zherikhin 1999). This specimen bears several
anomalous features: a large size of 17 mm in length; well-developed, compound eyes;
a pair of peculiar, horn-like appendages extending laterally from each side of the head;
long and ambulatory legs; widely separated leg bases; a pair of robust spines behind
the forecoxae; and exceptionally small claws. These characters are atypical compared
to modern species of Phthiraptera. The initial, reasonable, attribution of the
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution