Vol 10 Part 14. An introduction to the immature stages of British Flies ...

ll Antennae (an) prehensile (adapted for holding or seizing), with long strong apical spines;
without distinct mouth-brushes; thorax and 7th abdominal segment with paired pigmented
air sacs (as). Larvae active, but hold a horizontal position in the water betwee n
movements; in still or slow moving water (figs 45-46) . Chaoboridae (p. 39)
Antennae not prehensile, without strong apical spines; with distinct mouth-brushes, one on
each side of labrum (figs 43-44, br); no pigmented air sacs. Larva active but usually hold
an oblique (fig. 44) (horizontal in Anopheles fig. 43) position at the surface of the water
between movements; in still or slow moving water (figs 43-44) . Culicidae (p. 39)
12 Body with short tubercles or spinous processes on all segments; anal segment with longer
processes; respiratory system holopneustic with 10 pairs of spiracles. Larvae inactive,
characteristically curved in life; usually communal in decaying organic matter, rich soil,
plant roots, dung, etc. (figs 74-78) Bibionidae (p. 47)
Body otherwise; less than 10 pairs ofspiracles present . 13
13 The two posterior spiracles each on the tip of a cylindrical process (except Eclaetia fig . lOO).
Larvae usually dark or at least brown or yellow and rather hairy; very inactive; in dung,
soil or in drier habitats with decaying material, e.g. birds' nests, tree holes (figs 92 ~ 100)
Scatopsidae (p. 50)
The two posterior spiracles not on such processes 14
14 Last abdominal segment usually with a short non-retractile respiratory tube (figs 30, 32) or
tergites of body with numerous distinct transverse sclerotized plates (figs 31 ~ 39) (except
Trichomyia, fig 40); sometimes body with numerous processes. Larvae rather inactive, in
decaying organic matter in aquatic or semi-aquatic situations (figs 30-40)
Psychodidae (p. 37)
Last abdominal segment without such a tube; abdomen without distinct transverse
sclerotized plates . 15
15 Abdominal segments subdivided superficially into 3 more or less equal parts (fig. 5);
posterior spiracles surrounded by four fleshy lobes (figs 6-8). Larva whitish to brownish,
slow moving; in drier dung, soil, or in moist habitats with decaying organic material
(figs 2~ 8) Trichoceridae (p. 35)
Abdominal segments not subdivided superficially into three more or less equal parts . 16
16 Abdominal segments 2-6 divided superficially into two unequal parts (figs 70-71); posterior
spiracles surrounded by 5 reduced lobes (figs 72~73). Larvae slender, active; in moist
habitats where decaying organic material occurs, in deliquescent fungi, or in drier habitats
such as dung, soil, old plant stems, etc. (figs 70-73) . Anisopodidae (p. 46)
Abdominal segments not so divided; sometimes superficially ringed but in this case the rings
are narrow, darker and equal; anal segment without lobes. Larvae usually white with
contrasting darker, often black head capsule . 17
17 Head capsule ventrally with epicranial plates meeting only at one point (or not meeting,
Diadocidiinae) so that the posterior tentorial bridge is absent (fig. 86); or if the bridge is
partly formed the abdominal creeping welts have sclerotized spicules. Larvae usually
white, sometimes dull yellow to bright green; usually in fungi , under bark, in silken webs in
holes in old tree trunks, in soil, decaying plants, roots etc . Mycetophilidae (p. 47)
Head capsule ventrally meeting at two points, the posterior tentorial bridge (ptb) being
complete (figs 87~88) or nearly complete; abdominal creeping welts without sclerotized
spicules. Larvae white with black head capsule; in decaying plant material, animal
excrement, rotten wood attacked by fungus, some in old nests of mammals and birds,
sometimes mass movements in large columns . Sciaridae (p. 50)
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