Spinnerets silk spigots morphology of Araneidae, Tetragnathidae, Theridiidae and linyphiidae (Araneae: Araneoidea)

Abstract

The morphology of spinnerets silk spigots in araneoid species was studied mainly with SEM. Adult females of Araneoidea had two pairs of ampullate spigots and three pairs of cylindrical ones, and most of them had a pair of flagelliform spigots and two pairs of aggregate ones on their spinnerets. These results appeared to be the evidence for the monophyly of Araneoidea. Families of Araneoidea could be distinguished from each other by the differences in the silk spigots morphology. For example, Theridiidae had huge aggregate spigots. Silk spigots morphology was also shown to be useful for re-examining the taxonomic position of species. For example, Achaearanea and Theridion included the species both with a pair of aggregate spigots and with two pairs of the spigots. It was also shown that the number of aciniform spigots and the size of aggregate spigots were related to the difference in predatory behavior of spiders.