Enoplognatha

The genus Enoplognatha is found within the the family Theridiidae, the cobweb spiders. Most members make chaotic webs on or near to the ground in leaf litter, under logs or beneath larger rocks (Levi, 1957a). The webs of E. ovata are often in the shrubs and herb layer of woodland understories (in my experience).

There are four members of this genus that are found in Minnesota. Identification is not always straightforward. The native members of this genus are nondescript and easily confused with one another (beware of misidentified images on the internet). They can also be confused with some members of the genus Steatoda. The other member of the genus known from Minnesota is a non-native species that occurs in two different morphs and is more easily confused with spiders found in the genus Theridion. We'll start with the easy one...

E. ovata or Candy-striped Spider is the non-native Old World species that has become firmly entrenched in the spider fauna of North America. When Herbert W. Levi wrote his paper on the members of this genus in 1961 it was only known from small parts of the Pacific Northwest and the northeastern U.S. This species has been spreading steadily westward across the state of Minnesota and is known from Lake County south to Houston County and west to Blue Earth County (with an outlier in Murray County to the west). The carapace has a smudgy dark midline with black edges but shows two different patterns on the creamy white abdomen: 1) a pair of pink, undulating longitudinal stripes and 2) a pair of longitudinal rows of distinct or indistinct black spots. Theridion frondeum can be visually similar but is smaller and the dark midline on the carapace is often forked. An example of the pink-striped version: https://www.inaturalist.org/observations/5554755. An example of the spotted version: https://www.inaturalist.org/observations/173920430.

E. caricis has a Holarctic distribution and can be found across Europe, Russia, China and much of North America. Levi indicates that the legs, carapace and chelicerae are all yellow-brown but the sternum is dusky brown. He describes the abdomen as white, brown and black with a folium and ventral median black band bordered by a gray line on each side; the sides of the abdomen have white streaks on a black background (1957a). If that nondescript description doesn't help, perhaps you can look at a couple of my voucher specimens. Here's one on BugGuide: https://bugguide.net/node/view/736074/bgimage. Here's one from iNaturalist: https://www.inaturalist.org/observations/120703266.

E. marmorata or Marbled Cobweb Spider is only found in North America where it is widespread. Kaston indicates the legs and cephalothorax are yellowish brown with a gray to white abdomen that has two patterns, each with a dark linear blotch in the middle (1948). One pattern is very similar to that of E. caricis but the folium pattern is usually scalloped (and silvery in some specimens) (Kaston, 1948). The other pattern consists of 4 pairs of irregularly shaped spots on a whiter background (which is very similar to Steatoda albomaculata). To further complicate the identification is that some individuals can be very dark while others can be pale. Abdomen pattern 1: https://bugguide.net/node/view/1054551/bgimage. Abdomen pattern 2: https://www.inaturalist.org/observations/51028483.

E. intrepida is known from the U.S., Canada and Greenland. Levi indicates that the legs and cephalothorax are yellow-brown, the latter with a dusky line around the margin . He also indicates the abdomen is gray-brown with a dark mark in the median area, 4-5 dark spots on each side and light-colored fine spotting on a dark background on the underside and sides (1957a). Kaston indicates this species is typically paler than E. marmorata (1948). This species is poorly understood in Minnesota and is only known from a record from Clearwater County. A couple of research grade observations can be seen here: https://www.inaturalist.org/observations/206279662 and here: https://www.inaturalist.org/observations/165986715.

Sources
•Kaston, B. J. 1948. Spiders of Connecticut. Bulletin of the Connecticut State Geological and Natural History Survey 70: 1-874.

•Levi, H. W. 1957a. The spider genera Enoplognatha, Theridion, and Paidisca in America north of Mexico (Araneae, Theridiidae). Bulletin of the American Museum of Natural History, 112(1):1-124.

•Levi, H. W. 1961. The spider genera Steatoda and Enoplognatha in America (Araneae, Theridiidae). Psyche, 69:11-36.

Posted on May 25, 2024 03:26 PM by cheins1