Hymenoepimecis argyraphaga
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| Hymenoepimecis argyraphaga Gauld, 2000 |
Hymenoepimecis argyraphaga is a parasitoid wasp whose host is the spider Plesiometa argyra. The wasp is unique in modifying the spider's web building behavior to make an X-shaped web designed to support the wasp's cocoon without breaking in the rain.
The wasp temporarily paralyzes the spider and lays an egg on her abdomen. It hatches into a larva which sucks blood through a small hole, while the spider goes about her normal insect-catching. When the larva is ready to pupate, it injects a chemical into her, causing her to skip the spiral-drawing steps and retrace radial lines. When the spider is finished - which isn't totally obvious as she sits motionless in the middle of the web when she would be drawing spirals - the wasp larva molts, eats the spider, builds a cocoon hanging from the middle of the X, and pupates.
Normal orb weaving consists of several steps:
- Build a frame. This may require throwing a line into the wind and hoping it catches somewhere.
- Find the center by drawing two diagonals.
- Draw a sequence of radii.
- Draw a loose spiral of nonsticky silk, about five times the spacing of the final sticky silk.
- Draw the tight spiral, erasing the loose spiral.
The modified web consists of two diagonals, sometimes the frame, and radii which are not properly spaced but laid over the original four radii. A few strands are placed in the middle.
[edit] References
- Ian D. Gauld (2000). The re-definition of pimpline genus Hymenoepimecis (Hymenoptera: Ichneumonidae) with a description of a plesiomorphic new Costa Rican species. Journal of Hymenoptera Research 9: 213-219.
