Alloreferent and Apparent Seasonal Polyphenism of Dielis tejensis with an Updated Key to Nearctic Dielis Species (Hymenoptera: Scoliidae)

TL;DR

This paper describes a new species of parasitic wasp, Dielis tejensis, and its unique seasonal traits, along with an updated guide to identify related species.

Contribution

The discovery of the female form of D. tejensis and the first report of partial seasonal polyphenism in Scoliidae wasps.

Findings

The female of Dielis tejensis was identified and described for the first time.

D. tejensis exhibits partial seasonal polyphenism, a phenomenon not previously documented in Scoliidae.

The species shows a male-biased sex ratio, possibly due to aestivation in female immature stages.

Abstract

The family Scoliidae consists of parasitoid aculeate wasps with taxonomy that has long been problematic due to frequent interspecific similarities and plesiomorphies which complicate phylogenetic analyses. The biology of Scoliidae is also not yet fully understood, despite their importance for science and the economy. This article describes the female of a recently discovered species of Scoliidae from North America, Dielis tejensis. It also presents an updated key for identifying Nearctic representatives of Dielis, reports partial seasonal polyphenism in D. tejensis, a phenomenon previously unknown in Scoliidae, and hypothesizes about what the similarity of the ranges of D. tejensis and one of its major nectaring plants, Hymenopappus artemisiifolius, may indicate.

Scoliidae are fossorial aculeate wasps (Hymenoptera: Apocrita) whose larvae develop as parasitoids of beetle grubs, mainly from the family Scarabaeidae. Despite their distinctive appearance and economic importance, the taxonomy and biology of Scoliidae are less well understood compared to other Hymenoptera. Recently, a new species of Scoliidae, Dielis tejensis Szafr., was described based on about a dozen male specimens from Texas (Nearctic realm). This article reports on mtDNA-verified discovery of the female D. tejensis. As in the case of other members of the tribe Campsomerini, D. tejensis exhibits strong sexual dimorphism in body structure and color pattern. Females of D. tejensis most closely resemble Dielis plumipes (Drury) and were previously confused with D. plumipes fossulana (Fabr.), with which D. tejensis is partially sympatric. D. tejensis has more than one generation per year, characterized by a male-biased sex ratio, perhaps resulting from the female immature stages entering a state of aestivation. The multi-generational developmental cycle of D. tejensis correlates with the existence of a partial seasonal polyphenism in this species. The data presented also shows a similarity in the distribution ranges of D. tejensis and one of its main nectaring plants, Hymenopappus artemisiifolius DC (Asteraceae), that may suggest similarity in the environmental requirements of both organisms or specialized trophic relationship between the still-unknown beetle host of the wasp larvae and H. artemisiifolius or another plant with a similar range. D. tejensis has been included in the accordingly modified key to the Nearctic species of Dielis Sauss. & Sichel, which is also presented here.

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