Nesting Biology of the Potter Wasp Ancistrocerus flavomarginatus (Hymenoptera, Vespidae, Eumeninae) Revealed by Trap-Nest Experiments in Southern Brazil.

This paper provides the first description of the nesting biology of Ancistrocerus flavomarginatus (Brèthes) (Hymenoptera, Vespidae, Eumeninae), the only species of the genus found in Brazil. Our trap-nest experiments were conducted in two Mixed Ombrophilous Forest fragments and two adjacent matrices in Guarapuava (Paraná state, Brazil) from August 2017 to July 2018. In each area, we set 192 trap nests divided into six groups of 32 units, totalling 768 trap nests. We obtained a total of 47 nests of A. flavomarginatus, the vast majority of them (43, 91.5%) founded in the forest fragments. Most nests were built in wooden traps with a bore diameter of either 5 or 7 mm (19 nests in each type, 80.8%). Nests comprised 1-12 subcylindrical brood cells arranged linearly and separated from one another by transverse partitions of soil mastic. Larvae consumed 6-10 lepidopteran caterpillars before spinning the cocoon. Ancistrocerus flavomarginatus produced up to 6 annual generations (multivoltinism) and its immature forms were parasitized by chrysidid and ichneumonid wasps. The calculated sex ratio (1.78:1) was statistically biased towards males, but since they (21.3 ± 2.0 mg) were significantly lighter than females (50.9 ± 4.0 mg), the resulting investment ratio (1.34:1) was female biased. Males emerged from more external cells and developed significantly faster (27.2 ± 0.46 days) than females (30.1 ± 0.66 days), hence a case of protandry. We demonstrated that A. flavomarginatus is largely dependent on the Atlantic Rainforest and thus that deforestation poses a critical threat to this important species.

Description of the male, nest architecture and biology notes of Zethus plaumanni Bohart amp; Stange, 1965 (Hymenoptera, Vespidae) in southern Brazil.

Although diverse and widespread, there is much to improve on the knowledge of Zethus Fabricius, 1804 wasps. This includes aspects of many areas, such as data on taxonomy, behavior and biology. In the present study, we investigated Zethus plaumanni Bohart Stange, 1965, a species hitherto known only from the female type in the literature, and worked to fill gaps on the knowledge of this species by describing the male and its genitalia, the nest structure and giving notes on the biology of individuals collected in trap-nests in southern Brazil. The male is diagnosable by characters also used for female identification. The nest follows the pattern of typical pre-existing cavity users, with a remarkable multi-layered nest plug. Sex ratio follows the 1:1 rule and sampling indicates diapause in the adult phase.

Zethus (Zethus) pilosus Zavattari, 1912 (Hymenoptera: Vespidae: Eumeninae) from Southern Brazil: description of the female, the male genitalia, its nest and notes on biology.

Zethus is the largest vespid genus and, despite being very diverse in the Neotropical region, little is known about its biology and many species are known from only one sex. Zethini are centered in one of the controversies involving Vespidae phylogeny; increased knowledge of terminals will allow for more precise analyses, because some phylogenetically informative characters are observed in only one sex and others can be extracted from nests. With this in mind, complementary knowledge on Zethus pilosus is presented: the description of the female, of the male genitalia, of the nest and notes in its biology. Additional key features in the pronotum for identification of this species are provided. Nests were founded between December and April, presenting construction of partitions out of a combination of mud, sand, vegetable matter and insect parts. Development from egg to adult lasted an average of 39 days.