Dictyna coloradensis, a small spider(9) that lives in Canada and the United States(2,3), is of special interest for several reasons. This spider, with a carapace (the upper surface of the front part of the body(11)) that’s only between 1.1 and 1.26 mm (0.04-0.05 in) wide(13), weaves an unevenly-shaped web(9) on the branch-tips of shrubs8, on the flowering stalks of plants (9,12), and on trees(7), in part out of an old type of silk called cribellate silk (5,13). Each thread of this silk contains hundreds or even thousands of tiny fibers which are good at snagging insects such as flies (4,7) and ants(8), despite having no gluey liquid(1,10). Unlike most spiders(14), Dictyna coloradensis mothers live in these webs together with their spiderlings for a time, taking care of them by sharing the insects that they catch with them(12,13). Dictyna coloradensis is also important because, as is the case with many other spiders(6), these insects which it eats are often crop pests—it sometimes builds its web on fruit trees like apple and pear trees, and so it catches the insects, such as aphids, that like to feast on the fruits(7). However, this spider can also eat insects that are beneficial as weed-controllers. Certain weeds, such as yellow starthistle and spotted knapweed, which have invaded some grasslands in the western United States, are particularly good web-building locations forDictyna coloradensis (as well as for a very similar spider species, Dictyna major)(13). Because of this, there are large numbers of these spiders living among these weeds (9), and these spiders often capture the insects being used to destroy the weeds, making it harder to stop the weeds from spreading(13).
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