Notes on the biology of Trypoxylon (Trypargilum) opacum Brèthes (Hymenoptera; Crabronidae) in Southern Brazil

the present study investigated the abundance, seasonality and various life-history traits of trypoxylon (trypargilum) opacum. using trap-nests, 320 nests of t. opacum were collected in the parque municipal das araucárias in southern brazil (25° 23' 36" s and 51° 27' 19" w) over a 3 year period. nesting was more frequent during the warm season. nests consisted of a linear series of 1 to 8 brood cells separated by mud partitions, usually followed by an empty vestibular cell and final-closure mud plug. brood cells were most commonly provisioned with spiders of the family araneidae. sex-ratio was strongly female biased, 3.4:1 females:males. natural enemies attacking nests t. opacum included chrysidids, ichneumonids, sarcophagids, bombyliids and ants.