Order Diptera True Flies

Minute to large insects with a single pair of membranous wings, the hindwings reduced to small, drumstick-like halteres that function as balancing organs during flight; mouthparts suctorial but sometimes adapted for piercing. Metamorphosis complete. Eggs usually oval or cigar-shaped. often whitish or pale yellow, and often ornamented microscopically with a raised reticulated pattern. Larvae apodous and usually maggotlike, with a reduced, inconspicuous head.

Suborder NEMATOCERA

Adults with usually narrow bodies and slender, many-segmented antennae which lack an arista; antennae with a scape, pedicel and flagellum. the flagellar segments similar and often with whorls of hairs; maxillary palps usually 4- or 5-segmented and pendulous; wing venation with the anal cell 'open'. Larvae usually with a distinct head (but this may be retracted into the thorax) and with horizontally opposed, biting mouth-parts. Pupae obtect, the adult emerging through a T-shaped slit.

Fig. 79 A bark beetle, Scolytus mali - family Scolytidae (x15).

1. Family TIPULIDAE (crane flies)

Slow-flying insects with elongate bodies, wings and legs (the latter readily break off); ocelli absent; thorax with a distinct V-shaped suture (Fig. 80); wing venation includes a discal cell, and both anal veins (1A and 2A) extend to the wing margin (Fig. 81). Larvae fleshy but tough skinned (commonly called 'leatherjackets'); head deeply retracted and inconspicuous (Fig. 82); posterior end of body with often prominent papillae (Fig. 82a); soil-inhabiting.

EXAMPLES: Nephrotoma appendiculata (spotted crane fly), Tipula oleracea and T. paludosa (common crane flies).

Fig. 80 Dorsal view of the thorax of a crane fly family Tipulidae.

Fig. 81 Wing venation of a crane fly - family Tipulidae.

Fig. 79 A bark beetle, Scolytus mali - family Scolytidae (x15).

Fig. 81 Wing venation of a crane fly - family Tipulidae.

2. Family CERATOPOGONIDAE (biting midges)

Minute or small flies with piercing mouthparts and (in males) plumose or (in females) pilose antennae; ocelli absent; wings held flat over the body when in repose. Adults of some species suck the blood of vertebrates and cause considerable irritation to man and to farm animals. Larvae aquatic.

EXAMPLE: Culicoides spp. (biting midges).

3. Family CHIROMOMIDAE (non-biting midges)

Small, short-lived, gnat-like flies with the mouthparts poorly developed; thorax distinctly humped and often obscuring the head; antennae plumose in male, pilose in female; ocelli absent; forelegs often elongated. Larvae aquatic or inhabiting decaying organic matter.

EXAMPLE: Metriocnemus hirticollis (the larvae of which are often contaminants in consignments of harvested watercress).

4. Family SIMULIIDAE (black flies)

Minute, stout-bodied, short-legged, bloodsucking flies with piercing mouthparts; wings broad with thickened anterior veins; antennae 11-segmented; ocelli absent. Some species are of considerable local significance, inflicting painful

Fig. 82 A leatherjacket - family Tipulidae: (a) papillae at tip of abdomen.

'bites' on man and on farm animals such as horses. Larvae are aquatic.

EXAMPLE: Simulium reptans (common black fly).

5. Family BIBIONIDAE (St. Mark's flies)

Robust-bodied, often strongly pubescent flies; antennae arising form below the eyes (Fig. 83), 8-to 16-segmented but usually shorter than thorax; wings large, with strong anterior veins (Fig. 84); ocelli present. Larvae cylindrical, with a conspicuous head, well-developed mouthparts and often with distinct fleshy processes on the body (Fig. 85); spiracles often distinct. Larvae are particularly abundant in soil with a high organic content, and are sometimes damaging to the underground parts of plants.

EXAMPLES: Bibio hortulanus (March fly), Dilophus febrilis (fever fly).

Fig. 83 Head of a St. Mark's fly - family Bibionidae.

Fig. 83 Head of a St. Mark's fly - family Bibionidae.

Fig. 84 Wing of a St. Mark's fly - family Bibionidae.
Sciarid Fly Mushroom
Fig. 85 Larva of a St. Mark's fly, Bibio sp. - family Bibionidae (x4).

Fig. 86 Wing of a sciarid fly - family Sciaridae.

anal area anal area

Fig. 86 Wing of a sciarid fly - family Sciaridae.

6. Family SCIARIDAE (sciarid flies)

Small, delicate, gnat-like flies with a somewhat humped thorax; wing venation characteristic, with costa ending between R4+5 and M, (Fig. 86); antennae 16-segmented; ocelli present; compound eyes large and usually meeting above the antennae to form an 'eye-bridge'; palps usually 3-segmented (Fig. 87). Larvae elongate, translucent-whitish, with a conspicuous black head (Fig. 88).

EXAMPLES: Bradysia brunnipes (mushroom sciarid fly), Pnyxia scabiei (cucumber sciarid fly).

7. Family CECIDOMYIIDAE (gall midges) (p. 168 et seq.)

Minute to small, delicate flies with long, moni-liform antennae bearing whorls of hairs; wings

Fig. 87 Head of a sciarid fly - family Sciaridae.
Fig. 88 Larva of a sciarid fly - family Sciaridae.
Dasineura Wing
Fig. 89 Wing of a gall midge - family Cecidomyiidae.

broad, often hairy; venation much reduced, with few (mainly unbranched) longitudinal veins and no obvious cross-veins (Fig. 89); legs long and thin, the tibiae without spurs; ocelli absent. Larvae short, narrowed at both ends (Fig. 90), usually with a sternal spatula ('anchor process' or 'breast bone') (Fig. 90a) of characteristic shape for the genus or species; head reduced and

Fig. 90 Larva of a gall midge - family Cecidomyiidae: (a) sternal spatula.

inconspicuous. Most species are phytophagous, many inhabiting plant galls, but some are predacious on mites and other small invertebrates.

EXAMPLES: Contarinia pisi (pea midge), Dasineura brassicae (brassica pod midge), Haplodiplosis marginata (saddle gall midge), Mayetiola destructor (hessian fly), Resseliella theobaldi (raspberry cane midge), Sitodiplosis mosellana (orange wheat blossom midge).

Suborder BRACHYCERA

Usually stout-bodied flies with short, 3-segmented antennae which often terminate in a distinct apical style; palps 1- or 2-segmented and porrect. Larval head incomplete, generally retractile, and with vertically biting mandibles. Pupae usually obtect, the adult emerging through a straight or a T-shaped slit.

This suborder includes clegs, horse flies (family Tabanidae) and various predatory groups (e.g. families Asilidae, Dolichopodidae, Empididae and Therevidae) but no species that cause significant harm to crops.

8. Family TABANIDAE (clegs, horse flies, etc.)

Medium-sized to large, robust, blood-sucking flies with very large compound eyes; squamae large; feet with three arolia; antennae without a style but with the third segment annulated (Fig.

Annulated Antennae Horse Flies
Fig. 91 Antenna of a horse fly - family Tabanidae.
Fig. 92 Antenna of a therevid fly - family Therevidae.

91); mouthparts of females adapted for piercing and capable of inflicting a painful 'bite'. Larvae occur in damp situations, where they are carnivorous on soil-dwelling invertebrates.

EXAMPLES: Chrysops spp. (deer flies), Haematopota crassicornis and H. pluvialis (common clegs), Tabanus spp. (horse flies).

9. Family THEREVIDAE (stiletto flies)

Distinctly pubescent, thin-legged flies; antennae with a small style (Fig. 92); abdomen slender and pointed posteriorly; non-predatory. Larvae white, elongate and snake-like, with obvious segmentation; predacious on various soil invertebrates.

EXAMPLE: Thereva nobilitata (common stiletto fly).

10. Family HYBOTIDAE (dance flies)

Members of this family (formally included as a subfamily within the Empididae) are important predators of agricultural pests. The adults feed

Fig. 94 Antenna of a cyclorrhaphid fly - suborder Fig. 93 Wing venation of a dance fly - family Cycl0rrhapha.

Hybotidae.

Fig. 94 Antenna of a cyclorrhaphid fly - suborder Fig. 93 Wing venation of a dance fly - family Cycl0rrhapha.

Hybotidae.

mainly on Diptera (notably, Agromyzidae and Cecidomyiidae). The larvae are also predacious. Adults are characterized by their small size and rigid proboscis, and by the distinctive 'nick' (indentation) on the inner margin of the compound eyes; the tibia of each mid-leg often bears distinct spurs. Adults are distinguished from members of the Empididae largely on the basis of their wing venation - the veins usually extending to the wing margin without obvious forking (Fig. 93).

EXAMPLE: Platypalpus spp.

dorsal cornu

mouth-hook

Fig. 95 Cephalopharyngeal skeleton (mouthparts) of the larva of a cyclorrhaphid fly.

dorsal cornu

Cephalopharyngeal Skeleton

Fig. 95 Cephalopharyngeal skeleton (mouthparts) of the larva of a cyclorrhaphid fly.

11. Family DOLICHOPODIDAE (long-legged flies)

Adults are typically metallic bluish or metallic greenish, with (in males) often noticeably prominent genitalia. Most species are predacious on small insects, such as Collembola, Thysanoptera and other Diptera. The soil-inhabiting larvae are also predacious.

EXAMPLE: Dolichopus spp.

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