NESTING-BEHAVIOR OF ENCHEMICRUM-AUSTRALE (HYMENOPTERA, SPHECIDAE)

Adult wasps and six nests (20 cells) of the ground-nesting oxybeline Enchemicrum australe Pate were studied in Texas. Wasps constructed one to three cells each day in a cluster at the bottom of the main burrow or off short side burrows. A female wasp removed soil from her burrow by carrying pellets held between her open mandibles and forelegs and released the pellets some distance from the nest while flying backward. Nest entrances were usually secluded at the base of a plant or object (e.g., pebble). Wasps captured from 6 to 21 dolichopodid, sphaerocerid, or ephydrid flies of both sexes and placed them in a cell. A single egg was laid on a prey at the far end of the cell. Prey were transported venter up or on their sides and held with the wasp's middle and hindlegs. Provisioning wasps normally flew directly into their open nest entrances without landing but would impale the prey on the sting if forced to dig open a blocked nest entrance or walk on the ground. Three cells were infested with cleptoparasitic maggots and one of these was reared and identified as Metopia argyrocephala Meigen (Sarcophagidae: Miltogramminae). One other cell was destroyed by Forelius foetida (Buckley) ants. A comparison of the nesting behavior with that of Oxybelus suggests a close phylogenetic relationship. Every aspect of the behavior of E. australe can be found in one or more Oxybelus species.