Polideini

Polideini can be distinguished from other Tachinidae tribes by a combination of morphological characters and, more definitively, by their distinctive host associations. Members of this tribe exhibit a broader host spectrum than typical tachinids, with documented parasitism of arachnids and myriapods in addition to insects. Generic-level identification requires examination of chaetotaxy, male terminalia, and wing venation patterns. The tribe includes genera such as Hystricia, Lydina, and Lypha, which can be separated by details of facial profile, scutal setation, and abdominal shape.

Polideini has a broad distribution with records from multiple biogeographic regions. The tribe is represented in the Nearctic region (north of Mexico), where O'Hara (2002) provided a comprehensive revision. Multiple genera occur in the Neotropical region, including Argentina, Brazil, Chile, and Mexico. The tribe is also present in the Palaearctic region (Europe, Russia, China) and has been recorded from Taiwan, Japan, and various Pacific islands including Tahiti and French Polynesia. Specific distribution varies by genus, with some genera showing restricted ranges while others are more widespread.

Larval Polideini are parasitoids. The tribe exhibits exceptional host diversity within Tachinidae, with documented hosts including: insect larvae (Lepidoptera, Coleoptera, and other insects), spiders (Araneae), scorpions (Scorpiones), and centipedes (Chilopoda). This range extends beyond the typical insect-larva hosts of most tachinid flies. Specific host associations vary by genus and species.

• Araneae (spiders) - parasitoidunusual host for Tachinidae
• Scorpiones (scorpions) - parasitoidunusual host for Tachinidae
• Chilopoda (centipedes) - parasitoidunusual host for Tachinidae
• Lepidoptera larvae - parasitoidtypical tachinid host
• Coleoptera larvae - parasitoidtypical tachinid host

As with other Tachinidae, Polideini undergo complete metamorphosis with egg, larval, pupal, and adult stages. Females deposit eggs or larvae (depending on genus) on or near hosts. Larvae penetrate host bodies and develop as internal parasitoids, eventually killing the host. Pupation typically occurs in the host remains or in soil. Specific details of oviposition mode and larval development vary among genera.

Polideini functions as biological control agents of various arthropod populations. Their parasitism of spiders, scorpions, and centipedes represents a unique ecological role among Tachinidae, potentially regulating populations of these predatory arthropods. The tribe contributes to arthropod community dynamics through top-down population regulation across multiple trophic levels.

Some Polideini species have been investigated for biological control potential, particularly against pest insects. The broad host range of certain species may present both opportunities and risks for biocontrol applications. No species are known to be of direct medical or veterinary importance to humans.

• other Tachinidae tribesPolideini differs from related tribes primarily in host range; most Tachinidae are restricted to insect hosts, while Polideini regularly parasitizes arachnids and myriapods. Morphological distinctions require detailed examination of chaetotaxy and male terminalia.

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