Smooth muscle contracting compounds in venoms of sphecid wasps (Hym: Sphecidae)

1. The presence of smooth muscle contracting substances in venom preparations made from six species of sphecid wasps was investigated using a number of standard pharmacological techniques. 2. In addition, acetylcholine was identified by enzymatic degradation as well as by mass fragmentography, while histamine was determined using a radio-enzymatic method. 3. The venom reservoir of P. triangulum contains about 400 ng acetylcholine, but no histamine-, 5-HT- or bradykinin-like activity. 4. The venoms of the five other species contain histamine in amounts varying from 20 to 2000 ng per venom reservoir, but no acetylcholine-, 5-HT- or bradykinin-like activity.