Pelecinus

Wiedemann, 1823

American pelecinid wasps, snake-tailed wasps

Species Guides

Pelecinus polyturator(American Pelecinid Wasp)

Pelecinus is the sole living of the Pelecinidae, containing three restricted to the New World. Females are immediately recognizable by their extraordinarily elongated, thread-like that can exceed 5 cm in length, used to probe soil and deposit on scarab beetle larvae. The genus represents a relict lineage with extensive fossil diversity dating to the early Cretaceous across multiple continents.

Pelecinus polyturator by (c) Patrick Hanly, some rights reserved (CC BY), uploaded by Patrick Hanly. Used under a CC-BY license.

Alive Pelecinus polyturator by KristinLee. Used under a CC BY-SA 3.0 license.

Jardine Naturalist's library Entomology Plate 32 by Author James Duncan

Editor Sir William Jardine. Used under a Public domain license.

Pronunciation

How to pronounce Pelecinus: //pɛˈlɛsɪnəs//

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Identification

Females are unmistakable due to the snake-like, extremely elongated —no other North American approaches this . Males are more easily confused with small ichneumon wasps but can be distinguished by the swollen hind tibiae and shorter, widened abdomen tip. The combination of all-black coloration and inflated hind legs separates both sexes from superficially similar .

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Habitat

Mesic forests, woodland edges, and riparian corridors. are frequently encountered in hardwood forest understories and shaded areas. The requirements reflect the need for suitable scarab beetle in soil. Specimens have been recorded in both natural forests and landscaped areas adjacent to suitable habitat.

Distribution

New World only. Pelecinus polyturator occurs from southern Canada through the United States, Mexico, and Central America to Argentina. Pelecinus thoracicus is restricted to Mexico. Pelecinus dichrous occurs in South America. The has been recorded in humid mountain ranges of northeastern Brazil (Ceará state) and is present across the eastern United States west to the Rocky Mountains.

Seasonality

activity peaks in July and August in temperate North America, with some individuals persisting into September or rarely October. In tropical regions, activity corresponds with rainy season peaks—March in Ceará, Brazil.

Host Associations

Phyllophaga larvae (Scarabaeidae) - Larvae of 'May beetles' or 'June beetles' are the only documented . Females use elongated to probe soil and deposit directly on buried scarab .

Life Cycle

Larval development occurs within or on scarab beetle ; specific details of whether is internal or external remain undocumented. and pupae have been found in pasture soils. The complete duration is unknown.

Behavior

Females are active fliers, frequently attracted to lights at night. They engage in extensive , folding the elongated to reach it with hind legs. Males are rarely encountered, particularly in northern where may occur. location involves probing soil with the abdomen to detect buried scarab larvae.

Ecological Role

Specialized of scarab beetle larvae, potentially contributing to regulation of white in pastures and forests. The extreme morphological specialization suggests tight with scarab .

Human Relevance

No economic importance as a pest; non-stinging and harmless to humans. Occasionally encountered in urban parks and gardens adjacent to natural . Potential value as a agent for scarab pests, though not actively utilized.

Similar Taxa

Megarhyssa spp.Also large, striking with extreme ovipositor length, but proportions differ dramatically
Gasteruption spp.Have elongated and are sometimes mistaken for pelecinids, but lack the extreme attenuation and swollen hind tibiae

Misconceptions

The elongated is frequently mistaken for a giant stinger, causing unnecessary alarm. The is incapable of stinging humans. The rarity of males in northern has led to speculation about , though this remains incompletely confirmed.

More Details

Evolutionary significance

Pelecinidae represents a relict lineage with fossil diversity extending to the early Cretaceous (121–124 mya). Fossil pelecinids from that era include 43 in 12 across North America, Europe, and Asia, indicating the modern three species are remnants of a once-diverse group.

Reproductive biology

Males constitute only approximately 4% of collection records north of Mexico, suggesting either extreme rarity, shorter lifespan, or geographic in temperate . Thelytoky (production of females from unfertilized ) would be unusual in Hymenoptera given haplodiploid sex determination.