Orb-weaving spiders

Utetheisa, like many other Lepidoptera of the family Arctiidae, is aposematic. White, with pink hindwings and black and yellow markings (Figure 1 A), it is highly conspicuous on the wing. It flies as readily in daytime as at night. We suspected the moth to be unpalatable, and we were able to prove this in experiments with orb-weaving spiders. 

Garb, J. E., and Hayashi, C. Y. (2005). Modular evolution of egg case silk genes across orb-weaving spider superfamilies. PNAS 102, 11379-11384. 

From a defensive point of view, it was shown that sequestered PAs constitute an efficient protection against the orb-weaving spider Nephila clavipes, which liberates butterflies unharmed from its web. In this study, AT-oxides were shown to be more active than the corresponding free bases. This could be correlated with physicochemical properties of these molecules in interaction with the Nephila receptors. Moreover, there was a significant correlation between dosage and antipredator activity of PAs [160]. 

Olive, C. W. (1982). Sex pheromones in two orb weaving spiders, (Araneae, Araneidae) an experimental field study. Journal of Arachnology 10 241-245. 

Vasoconcellos-Neto, J. and Lewinsohn, T. M. (1984). Discrimination and release of unpalatable butterflies by Nephila clavipes, a neotropical orb-weaving spider. Ecological Entomology 9 337-344. 

Figure 12.3 Utetheisa ornatrix that were offered to the orb-weaving spider Nephila clavipes. The specimen on the right, rejected intact, was raised on one of its normal, pyrrolizidine alkaloid-containing food plants (Crotalaria mucronata). The one on the left, raised on an artificial diet devoid of alkaloid, was eaten. See also Figure 12.4. (From Eisner, 1982. American Institute of Biological Science.)...

Figure 12.4 Percent of prey item (Utetheisa, mealworms) remaining following attack by the orb-weaving spider Nephila davipes. Items were placed into individual webs with forceps (mealworms) or flipped from vials (Utetheisa).

Trivers R. L. (1985) Social Evolution. Benjamin Cummings, Menlo Park, CA. von Nickisch-Rosenegk E. and Wink M. (1993) Sequestration of pyrrolizidine alkaloids in several arctiid moths (Lepidoptera Arctiidae). J. Chem. Ecol. 19, 1889-1903. Vasconcellos-Neto J. and Lewinsohn T. M. (1984) Discrimination and release of unpalatable butterflies by Nephila clavipes, a neotropical orb-weaving spider. Ecol. Entomol. 9, 337-344. 

Figure 2 Orb weaving spiders produce different silkfibers tailored for different uses. Reprinted from Vollrath, F. Journal of biotechnology2000,74,67, with permission from Elsevier.

Kohler, T. and Vollrath, F., Thread biomechanics in the two orb weaving spiders Araneus diadematus (Araneae, Araneidae) and Uloborus walckenaerius (Araneae, Uloboridae). J. Exp. Zool., 1995, 271 1-17. 

Vollrath, F., Downes, M. and Krackow, S. Design variabUity in web geometry of an orb-weaving spider. Physiology Behavior, 1997, 62(4) 735-743. 

---