**3.1** *Philornis* **larval behaviour**

*Life Cycle and Development of Diptera*

and the postalar wall [1, 32].

as well as *P. downsi* with semi-hematophagous larvae.

based on larvae with distinctive posterior spiracles found parasitising nestlings. At this time, *Philornis* was suggested to be a synonym for *Protocalliphora* and assigned to the family Calliphoridae [26]. In 1921, Malloch [27] proposed the genus *Neomusca* based on adult specimens, whereas the genus *Philornis* was based on larval characters. Aldrich [28] revised this group and synonymized *Neomusca* with *Philornis* as independent genera, assigning both within the family Muscidae (Anthomyiidae at the time). This revision was supported by further work on *Philornis* species, as new and previously described species were transferred from other genera including *Hylemyia, Mesembrina, Neomusca* and *Mydaea* [9, 28–31]. *Philornis* adults are distinguished from other muscid genera by the presence of hair on the anepimeron

Using morphological and ecological data, *Philornis* can be divided into three phylogenetic groups: the '*aitkeni*-group', the '*falsificus-*group' and the '*angustifrons-*group' [33]. Male characters (given few female specimens) generally define the most basal lineage of *Philornis*, the '*aitkeni-*group', including enlarged upper eye facets in holotypic males [29, 33]. The members of this group display adult character states that are considered primitive among muscids (i.e., enlarged upper eye facets and presence of cilia on the surface of the wing vein R4+5) [33]. This group includes *P. aitkeni* (Dodge), *P. rufoscutellaris* (Couri), and *P. fasciventris* (Wulp). The phylogeny of the *aitkeni*-group is not completely resolved because of missing information about life history and morphology, as female and larval specimens are not available for many species. The second group, the *falsificus-*group, is defined primarily by *P. falsificus* (Dodge and Aitken), whose larvae are free-living [9]. Common morphological characters include five scutellar marginal setae that also place *P. fumicosta* (Dodge), *P. univittatus* (Dodge), *P. grandis* (Couri) and *P. sabroskyi* (Albuquerque) within this group [33]; however, data on the ecology of these species are missing. More information on larval life history is necessary to confirm whether species other than *P. falsificus* belong in this lineage. Despite a similar life history to *P. falsificus*, *P. downsi* is not within the *falsificus-*group [1, 9, 33], but forms a sister-group to all species within the *angustifrons*-group for which larval habits have mostly been documented (**Table 1**). The *angustifrons*-group is the most recently evolved and largest of the three *Philornis* lineages and contains species with subcutaneous hematophagous larvae

Comparative taxonomic analyses of *Philornis* species have been hampered by a lack of specimens and information [9]. For several species of *Philornis*, their morphological descriptions are based solely on one sex, generally males. In others, the holotype is missing or destroyed, and so other traits and ecological information are missing. *Philornis blanchardi* (Garcia) has been originally identified and described in Argentina from a single female specimen, which has since been lost [34]. This specimen may belong to a previously described species as it has not been captured and identified since, however the original description is considered sufficiently unique that it may be a separate species [34]. The single male holotype used to describe *P. umanani* (Garcia) has also been lost and due to the lack of detail provided in the original description, this species is deemed unrecognisable and is now considered a *nomen dubium* [34]. Evidence of a *Philornis* species complex within specimens of *P. seguyi* (Garcia) and *P. torquans* (Nielsen) in Argentina throws further doubt on the original taxonomic characterisation of many *Philornis* species [35]. These issues highlight the need for more extensive molecular and morphological analysis of currently recognised *Philornis* species to confirm species classifications and their evolutionary

**54**

relationships.

*Philornis* species differ in their larval feeding habits, which include coprophagous and hematophagous diets (**Table 1**). Larval habits have been documented for 30 out of 52 described species (**Table 1**). The most basal group in the *Philornis* phylogeny (*aikteni*) have free-living coprophagous larvae [33]. These larvae parasitise cavity nesting host species that do not remove waste, such as the rufous-tailed jacamar (*Galbula ruficauda*) Cuvier (Piciformes: Galbulidae) and appear to be specific to this type of nest [2, 5, 30, 36, 37]. Free-living saprophagous larvae in the nest are regarded as the ancestral trait, evolving into coprophagous larvae, semi-hematophagous larvae and then subcutaneous larvae [9, 33]. This transition is also supported in *Passeromyia* where species show a similar order of descent [4, 10, 33]. Two documented species, *P. downsi* (*angustifrons*-group) and *P. falsificus* (*falsificus-*group)*,* have free-living and semi-hematophagous larvae, although other undescribed species within the *falsificus-*group may also have free-living larvae [1, 30, 33].

Most *Philornis* species (83%) have larvae with subcutaneous hematophagous feeding habits, which is also the primary larval strategy in the *angustrifrons*-group. Within this group, only *P. downsi* has non-subcutaneous larvae. The semi-hematophagous *P. downsi* larvae may be similar to *P. falsificus* (*falsificus*-group), which is also suspected of having free-living semi-hematophagous larvae [33]—but not enough is known about the biology of the *falsificus*-group. While *P. falsificus* is considered a free-living ectoparasite [30], this assessment is limited by the observations to date of later instars and puparia [38, 39]. On the other hand, in two species with subcutaneous feeding habits in the *angustifrons-*group, a few *Philornis* larvae have been also observed in avian nares. Specifically, *P. mimicola* larvae have been found in the nares of ferruginous pygmy-owl nestlings (*Glaucidium brasilianum*) Gmelin (Strigiformes: Strigidae), but most larvae occurred subcutaneously [40]. Larvae of *P. porteri* (Dodge) have been found in the nares and ear canals of some nestlings [41, 42], and 3rd instar larvae observed to feed externally on the abdomen and wings of their hosts [41, 43]. In the semi-hematophagous *P. downsi* larvae, 1st instars regularly reside within the avian nares [44–46] and later instars move to the base of the nest where they emerge at dusk and dawn to feed externally on the blood and tissue of the developing birds [45, 46]. Lineages with free-living larvae have been far less studied than lineages with subcutaneous larvae (**Table 1**). Free-living larvae move freely within the host nest, detach from the host at various times and reside in the nest base during the day, making them less conspicuous to human observers [45, 46]. In contrast, subcutaneous larvae reside under the skin of the host and hence can be detected when nestlings are examined.
