Agricultural entomology: The order of Diptera

Agricultural entomology: The order of Diptera

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Bibliographic reference:
Phytopathology, agricultural entomology and applied biology” – M.Ferrari, E.Marcon, A.Menta; School edagricole - RCS Libri spa

Diptera are widespread everywhere, from the plains at sea level to the mountainous regions, they include about 85,000 species of insects, generally of small and medium size; however, there are also large Diptera. Normally they have inconspicuous colors even if, at times, with metallic reflections; in some families there may be liveries similar to those of bees or wasps, for mimicry, in order to escape predators. Distinctive feature of Diptera, compared to other insects, is the presence of only one pair of membranous wings, the front ones. (Diptera = two wings). The hind wings are transformed into balance organs for flight, the rockers; these can be clearly visible or not visible, because they are protected by a scale. The head, free and mobile, generally has two large compound eyes and usually three ocelli. The antennae can be long and filiform (suborder of Nematoceri), or short and stubby at the base (suborder of Brachiceri).

The mouthparts of adults can be of different types:

  • Pungent-sucking, as in Culicides (mosquitoes)
  • Pungent-sucking-lambing, as in the Tabanids (horsefly)
  • Lambente-sucking, as in the Muscidae (fly)

The legs are ambulatory type; in certain groups the tarsi end with two nails and structures suitable for adhesion (pulvilli and, sometimes, empodio). Some families have particularly elongated and slender legs. The head and chest are often covered with bristles. The abdomen, of variable shape and size, consists of 10 segments, some more or less merged together; in females of some families, the last abdominal segments form an extra-flexible and sometimes very long replacement ovipositor. Reproduction is generally amphigonia and most of the species is oviparous; some Diptera, especially among parasitic forms, are viviparous. The eggs generally have a cigar shape. The development is holometabolo however some species are hypermetabola.
The larvae, white or yellowish, have a soft integument, are apode and without eyes. They normally move by contraction of the body; some species carry bristles or particular processes that assist movement. Many larvae are aquatic; others live in the soil, often among decaying organic materials, and some in the living tissues of animals and plants. The mouthparts of the larvae are chewing, more or less modified; in the more advanced Diptera, Brachiceri Ciclorafi, the mouth apparatus is made up of only two hooks, capable of tearing and perforating the tissues. The pupae can be protected, by a draft bed, or unprotected (naked pupae). In the upper Diptera (Brachiceri Ciclorafi) the pupae, which unlike the other Diptera are not mobile, are protected in a puparia; this is constituted by the last larval exuvia which hardens. The Diptera diet is extremely varied, so much so that we can have blood-sucking species, or species that feed on plant residues, or decomposing animals and others that use sugary substances, such as nectar; various species are lithophagous at the larval stage. In animals they withdraw blood or in any case cause disturbance and can be a vehicle for pathogens; mosquitoes of the genus Anopheles, for example, are intermediate hosts of the Plasmodium of malaria which is transmitted to man by inoculation with the saliva of the insect. In plants they can cause significant damage to both crops and spontaneous plants. Furthermore, as a consequence of the attack of some Diptera, galls can form and finally they can be vectors of pathogenic microorganisms. Some species (useful Diptera) carry out intense parasitic and predatory activity against various phytophagous insects; many species also facilitate the decomposition of organic materials of plant and animal origin. The Order of Diptera is divided into two suborders: Nematoceri and Brachiceri.

Suborder Nematoceri

The more primitive Diptera belong to this suborder, they are distinguished by long and filiform antennae, by the shape of the slender and elongated body.
The larvae are terrestrial, linked to humid or aquatic environments.
The pupae are almost always free and capable of movement

Tipulidae family

The Tipulids are one of the largest Nematoceri families; these Diptera have medium dimensions, sometimes they can reach even large dimensions, as happens in the giant Tipula which exceeds 60 mm of wingspan.
The larvae live, in the majority of cases, in the ground among the decomposing plant debris; however they can also live in fruits, leaves and some have aquatic habits.

Cecidomìdi family

The Cecidomìdi family constitutes a vast grouping (about 1500 species) of Nematoceri.
They are small insects, generally of the order of a few mm in length; they have hairy wings and thin, long legs.
The females, equipped with a long replacement ovipositor, lay their eggs on the surface or inside the plant tissues, often causing malformations or gall (or cecid) formations, hence the name of the family.
The larvae, white or yellow-orange, generally feed on plant tissues; however, some are predatory or act as parasites of various insects such as Aphids, Mealybugs, Psyllas and Mites.
Among the species belonging to the family we remember:
Dasyneura pyri (Bouche) is Contarinia pyrivora (Riley), which attack the pear tree.
Among the species of considerable interest for biological control applications it is worth mentioning Aphidoletes aphidimyza (Rond.), predator of aphids.

Culìcidi family

Common mosquitoes belong to this family.
The females have a pungent-sucking mouthparts with which they can sting and suck the blood; males, due to changes in the mouthparts, can only lick sugary liquids for which they are unable to sting.
The larvae, typically aquatic, are equipped with a chewing mouthparts and feed on aquatic vegetation.
Among the common species in our country we only mention:
Culex pipiens L., Common mosquito.

Suborder Brachiceri

The most advanced Diptera belong to this suborder, they are distinguished by short antennae, consisting of a few articles. The body, compared to the Nematoceri, is more squat and the legs are more robust and short, even the wings are stronger.
The larvae generally have the head more or less reduced and retracted in the thorax and are equipped with a chewing mouth apparatus or a cephalo-pharyngeal skeleton, in which the jaws are transformed into two hooks that move vertically (Cyclorophs).
Pupae are almost always protected by the puparia.
The adults depending on how they flicker, are distinguished in: Ortorafi and Ciclorafi.
In Ortorafi the adult flickers from a longitudinal dorsal opening in the thoracic region (e.g. Tabanidae).
In the Cyclorafi the flicker occurs through a round opening, with the lifting of an operculum, at the apex of the pupary (e.g. Sirfidi, Agromizidi).
Numerous parasitic species of humans and pets belong to the Brachiceri, carriers of various diseases.

Agromyza nana - Agromizidi family (photo Paul Fontaine

Suborder Brachiceri (Ortorafi section)

Tabànidi family

The Tabànidi, commonly called Tafani, are insects of medium and, sometimes, large size of the body.
The smaller males of the females feed on nectar, honeydew and other sugary liquid substances of the plants; the females, equipped with a mouthparts capable of pricking and sucking, feed on the blood of various animals and also of man. They are particularly troublesome for cattle (cattle and horses) for irritating bites, due to saliva that contains anticoagulant substances, and for the removal of blood.
The Tabànids frequent, in particular, the hot areas with high humidity; these places are also suitable for oviposition that occurs in water or in particularly moist soil.
The larvae develop in these environments predating various insects, other arthropods, molluscs and worms; in some cases even small amphibians and other invertebrates.
These insects are responsible for the spread of various diseases, both of animals and humans, especially in tropical regions where they are particularly widespread.

Suborder Brachiceri (Cyclore section)

Sirfidi family

The Sirphids are medium-sized Diptera (10-15 mm in length); the livery is showy, sometimes with metallic reflections and whitish, yellow, orange spots or bands in the abdomen.
The adults feed on nectar and pollen, typically remaining suspended in midair and jerking; they perform a fair pollinating function.
The larvae feed on decomposing materials; some phytophagous, like Lampetia equestris F., whose larvae feed on bulbs, others are entomophagous, especially predators of aphids, such as Syrphus ribesii L. and Episyrphus balteatus (Deg).

Volucella pellucens - Sirfidi family (photo Paul Fontaine

Tripètidi family

Tripètidae are small insects (about 5 mm long); they often have a livery with flashy spots and patterns on the body and wings.
The adults have a sucking-sucking mouthparts and visit the flowers whose nectar they suck; sometimes they feed on rotting plant materials.
The abdomen of the females is elongated and carries a replacement ovipositor, sometimes very developed and sclerified, with which they lay their eggs inside the plant tissues.
The larvae, with cephalo-pharyngeal mouthparts equipped with robust hooks, are mainly endophytes and live by feeding on fruits, leaves, stems or other plant parts, often causing serious damage to plants.
Various species harmful to fruit trees belong to the Tripètidae, among these we remember:

Bactrocera oleae Gmel., Olive fly;
Rhagoletis cerasi L., Moscow of cherries;
Ceratisis capitata Wied., Fruit fly.

Agromìzidi family

Agromìzidi are Diptera of small and very small dimensions (from 1 to 3 mm in length).
The adults, equipped with a lambent-sucking mouthparts, feed mainly on sugary substances and nectar; they prefer cool and wet areas such as woodlands.
The females have a replacement ovipositor which can also be very long and robust; this, in addition to being used for laying eggs on or in plant tissues, can also be used to engrave plant tissues and obtain lymph.
The larvae dig sinuous tunnels within the mesophyll of the leaves and, sometimes, even in the stems (mining larvae); they pupate in a puparia within plant tissues or in the ground.
Agromìzidi group many species that cause damage to crops, among these we remember:
Liriomyza trifolii (Burgess), which causes serious damage in the greenhouse.

Antomìidi family

The Antomìids are small and medium-sized Diptera with an appearance similar to that of common house flies.
The adults feed mainly on flower nectar and on liquids of decomposing organic materials.
The larvae can feed, like adults, on decomposing substances or excrements and finally on plant tissues (leaves, flowers, stems, bulbs, etc.) where they dig tunnels.
Among the species that feed on plants we mention:
Pegomya betae Curt., Beet fly attacking the chard leaves.

Larvevòridi or Tachìnidi family

Larvevòridi are insects of varying sizes, from small to large; the body is robust and covered with large bristles distributed variously according to the species.
The adults feed mainly on sugary liquid flowers and honeydew. The larvae, on the other hand, are parasites, mainly endophagous, of larvae of various phytophagous insects (especially Lepidoptera) thus contributing effectively to their control, making themselves useful in biological control.
The females lay their eggs inside or near the victims' bodies; the larvae devour the victims from the inside, however keeping them alive until their pupation approaches, which almost always happens outside the host.
Among the species that show some interest in biological control we mention:
Leskia aurea Fall. It attacks mainly larvae of Egerid Lepidoptera, such as the Sesia del melo.

Muscidi family

Muscidae are small and medium-sized Diptera; include common house flies.
The body is covered with strong bristles, the chest is robust and the abdomen generally short; the well-developed head has two large compound eyes.
The mouthparts of adults are generally lambent-sucking, however in some species it is pungent-sucking and allows the incision of the host's skin to suck blood.
The larvae generally live among decaying organic materials; some are parasites of various animals including many birds.

Video: Cool Stuff: Jarod Beukelman on Entomology (May 2022).