An online resource based on the award-winning nature guide

Arachnids

Black Widow Spiders

9-29-14 northern black widow spiderBlack widow spiders have been found in every state. They are a lot less numerous in New England than further south — their abundance is inversely related to the latitude — however, the northern black widow, Latrodectus mactans, (pictured) is here. According to Dr. William Spear, a noted arachnologist and provider of the information in this post, a black widow in northern New England would need a very sheltered site, such as the south-facing walls of buildings, south-facing sides of ditches, or perhaps even in barns and sheds, in order to survive.

The web of the northern black widow is a rather small (for the size of the spider) messy tangle, usually constructed close to the ground. The spider is generally not found on the web, but in a silk-lined pocket to one side and above the web. The silk of widow spider webs is unusually tough, and with experience one can learn to differentiate it from other spiders’ silk just by testing the web with a stick or pencil.

If knowing that black widows cohabit your state causes some discomfort, rest assured. Their bites are very rare and almost never fatal. The few fatalities that have been recorded are generally from children or persons weighing less than 100 pounds, or with precarious health. (Photo taken by Evan Kay in North Pomfret, Vermont in September, 2014; submitted by Caroline Robbins)

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Birds & Ticks

7-18-13  song sparrow with tick 252Several recent studies demonstrate that wild birds are actively transporting ticks and their associated diseases during migration. In addition, a number of bird species are able to contract Borrelia burgdorferi (the bacterial causal agent of Lyme Disease infection) and transmit it to uninfected ticks that parasitize the birds for a blood meal. Since ground-feeding species such as Northern Cardinals, Gray Catbirds, Song Sparrows (pictured) and American Robins spend a significant amount of time foraging for food at the optimal height for ticks, they are excellent hosts and have all demonstrated the ability to infect larval ticks with Borrelia burgdorferi upon their first blood meal. (Look carefully at the Song Sparrow’s neck and you will find a tick.)


Spider Egg Sac

12-10-12 spider egg sac3 IMG_6616As a result of many years of evolution, spiders have developed the use of different silks produced by seven glands for various functions (ballooning, webs, wrapping prey, dragline, egg sac, etc.).  The tubuliform gland is responsible for the large diameter silk fibers used in the construction of egg cases.  Unlike other silk glands, which synthesize protein throughout a spider’s lifetime, the tubuliform gland synthesizes silk for only a short time in a spider’s life, just before eggs are laid.  This silk is synthesized only by female spiders, and is the stiffest type of silk, which makes it a very protective covering for eggs. The pictured overwintering spider eggs had three layers of protection:  bark (the photo is of the underside of a piece of loose bark), an outer silk cocoon covering the egg sac and the egg sac itself – a tough layer of silk covering the eggs. (Reluctantly I opened the sac for the sake of an educational photograph, and did my best to re-wrap the eggs.)