*COMMENT ~ Character notes. 
 
*CHARACTER NOTES 
#1. ~ (alternatively) is here used to indicate sometimes not unreasonably
included in or reduced to. 
#3. Note the essential distinction to be made between parasitic, referring as
here to the general life-style of a species; and the same term when it relates
to the precise feeding habits of the insects in their larval and adult stages
(q.v.). The different concepts are often confused in entomological literature. 
#14. 2-6 (recorded for many Brachycera sensu lato) probably usually means 3.
#18. Arista: in this context, a bristle-like extension of the terminal
antennal segment (in practice, usually of the third antennal segment of
Brachycera), with or without hairs or cilia, which may itself be segmented. 
#21. This character, featured prominently by Colyer and Hammond as
characterising the calypterate families, is here treated as unreliable for
identification on the advice of D.M. Unwin. 
#24. Ptilinum: an inflatable sac, exhibited above the base of the antennae by
(Brachycera-) Muscomorpha Schizophora, which is used by the emerging insect to
rupture the puparium. Its former presence is subsequently detectable on the
head, as a conspicuous groove between the face and the orbits. In groups where
it is found (viz., the Calyptratae and Acalyptratae), the ptilinal suture is
continuous with a crescentic depression (the lunule) over the bases of the
antennae. A lunule, unaccompanied by a clear ptilinal suture, also occurs in
some Aschiza. 
#25. Ocellus: a simple eye. Many Diptera exhibit 2 or three, towards the back
of the head between the compound eyes. 
#34. It may or may not be safe to treat functional as implicit, but for the
present this risky device has not been implemented. 
#35-36. For numerous families, the detailed constitution of mouthparts
(trophi) is not mentioned in any of the descriptions seen. 
#39. Porrect: extending more or lesshorizontally, or ascending, rather than
drooping. 
#40. Vibrissae: extra-large bristles, arising from the angles at the sides of
the mouth in many Brachycera \i{}sensu lato\i0{}. 
#41. Dorsal suture: a transverse groove on the sides or back and sides of the
thorax, between its front (prescutum) and middle (scutum) - i.e., in front of
the wings. It may be complete across the back of the thorax, discontinuous and
visible only laterally, or vestigial or absent. \par{}The dorsal suture is
(riskily?) assumed to be discontinuous or absent from the numerous families for
which it is not mentioned in the literature seen. Where explicitly stated to be
absent in the literature, it has been explicitly encoded as such. 
#42. Dorsal suture: a transverse groove on the sides or back and sides of the
thorax, between its front (prescutum) and middle (scutum) - i.e., anterior to
the wings. 
#43. Posterior calli: a pair of swellings, or callosities, one at each hind
corner of the back of the thorax (dorsum). Especially pronounced in Calyptratae.
#46. Hypopleural bristles: bristles borne on the hypopleura, i.e., on each
side of the thorax, above the insertion off the hind leg and below the posterior
thoracic spiracle. \par{}Hypopleuron: the hindmost, lower-lateral thoracic
plate. 
#52. Discal cell: a cell (of wide occurrence) bounded by veins 4 and 5.
Encoded here as absent in cases where it is described as confluent with the
second basal cell (i.e., where there is no delimiting cross-vein). 
#53. Sub-apical cell: a cell, at or near the wing apex, bounded by veins 3 and
4. Restricted to about a dozen families. 
#54. Anal cell: a cell (of wide occurrence) bounded by veins 5 and 6. It is
sometimes very small. 
#58. Costa: the stout nervure constituting the front edge of the wing.
\par{}This widely quoted character is here treated as unreliable for
identification, on the advice of D.M. Unwin. 
#59. Costa: the stout nervure constituting the front edge of the wing. 
#61. Data on the sub-costa mainly from Colyer and Hammond's family descriptions,
rather extensively extended from their illustrations and those of Colless and
McAlpine. 
#63. Data on the sub-costa mainly from Colyer and Hammond's family descriptions,
rather extensively extended from their illustrations and those of Colless and
McAlpine. 
#65. Vein 4 is generally identifiable as the one constituting the forward margin
in the discal cell (q.v.). 
#66. Vena spuria (false vein): a thickening of the wing membrane between and
parallel with the third and fourth veins, which is not joined to any vein.
Confined to and characteristic of \i{}Syrphidae\i0{}. 
#80. Calypters (squamae): flap-like appendages at the hind-bases of the
wings, or attached to the thorax close to the wing bases. Not to be confused
with the alula, which is often present as a conspicuous lobe in the hind
margin of the wing distal to the calypters. \par{}The upper calypter (alar
squama) occurs at the base of the wing; the lower calypter (thoracic squama) is
attached to the thorax. 
#92. Note the essential distinction to be made between parasitic, referring to
the general life-style of a species (q.v.); and the same term when it relates,
as here, to the precise feeding habits of individuals. The different concepts
are often confused in entomological literature. See the character concerned with
the feeding habits of larvae for further comments. \par{}In practice, the
distinction between parasitic and predatory is less clear than text-book
definitions usually suggest. The larvae of many Diptera and Hymenoptera, in
particular, contradict the common assertion that highly specialised parasitism
does not result in the death of the host (with the added, teleological
supposition that to do so is inimical to the long term survival of the parasitic
species). In fact, many dipteran and hymenopteran larvae universally described
as parasitic are highly adapted to keep the host alive only for as long as it
is needed as a source of food, before ultimately killing it. 
#94. Note the essential distinction to be made between parasitic, referring to
the general life-style of a species (q.v.); and the same term when it relates,
as here, to the precise feeding habits of individuals. The different concepts
are often confused in entomological literature. \par{}In practice, the
distinction between parasitic and predatory is less clear than text-book
definitions usually suggest. The larvae of many Diptera and Hymenoptera, in
particular, contradict the common assertion that highly specialised parasitism
does not result in the death of the host (with the added, teleological
supposition that to do so is inimical to the long term survival of the parasitic
species). In fact, many dipteran and hymenopteran larvae universally described
as parasitic are highly adapted to keep the host alive only for as long as it
is needed as a source of food, before ultimately killing it. 
#98. Puparium: a persistent, hardened and modified, usually barrel-shaped,
ovoid or globular derivative of the cuticle of the third larval instar,
functioning as a cocoon enclosing a thin-skinned pupa. In a few families (e.g
\i{}Stratiomyidae\i0{}), the last larval skin persists in unmodified form
(transitional puparia). 
