Lying on the dorsum: unique host-attacking behaviour of Zatypota albicoxa (Hymenoptera, Ichneumonidae)

摘要

Unique host enticing behaviour has been observed for the first time in Zatypota albicoxa (Walker), which parasitizes the house spider, Parasteatoda tepidariorum (Koch), which weaves irregular, three-dimensional webs. One female wasp lay on her dorsum on the floor and grasped one of the vertical gumfoot threads with her legs (reclining-style). The wasp picked the thread with her legs, feigning a captured and struggling prey. Although this behaviour seems to be a variety of the ambush style, it is quite similar to that of a wandering and captured wingless insect, and it seems an adaptation to the host being hidden in a complex web. As the wasp touched the gumfoot directly, this suggests the possession of behavioural or morphological mechanisms for avoiding entrapment by the sticky masses on the web. Diversity in mode of attack correlates with the fact that the spider constructs webs of various forms in a variety of situations. Digital video images relating to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo100416za03a, http://www.momo-p.com/showdetail-e.php?movieid=momo100415za01a, http://www.momo-p.com/showdetail-e.php?movieid=momo100416za01a, and http://www.momo-p.com/showdetail-e.php?movieid=momo100416za02a.