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Tachinidae

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Tachinidae is a massive and highly diverse family of true flies. These insects belong to the order Diptera. Scientists have identified more than 8,200 known species within this group. Many more species are still waiting to be discovered by researchers. In North America alone, over 1,300 species have been described. These flies live in almost every part of the world. They are especially diverse in the regions of South America.

10-Indian-Insect-Life - Harold Maxwell-Lefroy - Tachinidae
10-Indian-Insect-Life - Harold Maxwell-Lefroy - Tachinidae

Most members of this family are protelean parasitoids. This means the larvae are parasitic, but the adults are not. The larvae develop inside a living host and usually kill it. This is different from true parasites, which do not generally kill their hosts. Tachinid larvae feed on the tissues of the host insect. They can be endoparasites, which live inside the host's body. They can also be external, attacking from the outside. They often target caterpillars from moths and butterflies. However, they also attack beetles, grasshoppers, bees, and even centipedes.

Female tachinids use several different strategies to reach their hosts. Many females lay white, oval eggs on the skin of a host. Some genera, like Gymnosoma, use this method. Other species are ovoviviparous, meaning they deposit a hatching larva directly onto the host. For example, certain species in Ghana lay larvae on the Danaus chrysippus butterfly. Some flies use an ovipositor to inject eggs into the host. This organ is sometimes called an oviscapt, which means "egg digger."

Istocheta aldrichi egg on Japanese beetle
Istocheta aldrichi egg on Japanese beetle

Other species lay small eggs on the food plants of the host. This way, the host will eat the eggs by mistake. Some even use an ambush technique to attack a passing host.

Taxonomy, or the science of naming groups, is quite complex for this family. The name Tachinidae was first proposed by Robineau-Desvoidy in 1830. He originally called the group "Tachinariae." There was once confusion with a beetle family named by Fleming in 1821. To fix this, the ICZN invalidated the beetle name in 1993. They changed the beetle name to Tachinusidae. This ensures that Tachinidae refers only to these flies. Scientists still use physical traits to study and name these species today.

Adult tachinids have a very specific appearance. Most are drab and look like common house flies. However, they are usually more robust and bristly. They have three-segmented antennae and a prominent postscutellum. The postscutellum is a bulge located beneath the scutellum on the body.

10-Indian-Insect-Life - Harold Maxwell-Lefroy - Tachinidae
10-Indian-Insect-Life - Harold Maxwell-Lefroy - Tachinidae

Some species are brilliantly colored and resemble blow-flies. Their mouthparts can also vary greatly. Most are short-tongued and feed on easy nectar. Some have a long proboscis, which is a specialized mouthpart. The species Prosena siberita has a proboscis half its body length.

20170403 TachinidFly
20170403 TachinidFly

These flies are very important for both nature and agriculture. Many tachinids are natural enemies of insect pests. Farmers use them for biological pest control to protect crops. However, some species can be problematic. The Uzi fly is a notorious pest of silkworms in the silk industry.

Istocheta aldrichi egg on Japanese beetle
Istocheta aldrichi egg on Japanese beetle

Other flies, like Compsilura concinnata, are risky for biological control. This species uses at least 200 different hosts. This makes it likely to attack beneficial insects instead of just pests.

Adult tachinids also play a role in pollination. They visit flowers to get nectar for energy and pollen for nutrients. This helps them live longer and produce more offspring. They are particularly important pollinators in high-elevation ecosystems. In New Zealand, they are the most common visitors to alpine plants.

Ormia ochracea (gravid female)
Ormia ochracea (gravid female)

Some orchids have even evolved to use the flies. Certain orchids use sexual deception to trick male flies. The flowers mimic female tachinids to lure the males in. When the males attempt to mate, they move pollen from one flower to another.

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🖼️ Images & Media (6)
File:10-Indian-Insect-Life - Harold Maxwell-Lefroy - Tachinidae.jpg
10-Indian-Insect-Life - Harold...
File:Tachinid eggs on Leptoglossus.jpg
Tachinid eggs on Leptoglossus.jpg
File:Istocheta aldrichi egg on Japanese beetle.jpg
Istocheta aldrichi egg on Japanese beetle.jpg
File:Tachinidae.jpg
Tachinidae.jpg
File:Ormia ochracea (gravid female).jpg
Ormia ochracea (gravid female).jpg
File:20170403 TachinidFly.jpg
20170403 TachinidFly.jpg
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