Crustacean Deduction
Arthropods are invertebrates possessing an exoskeleton, a segmented body and paired jointed legs. Crustaceans make up one group of arthropods. Insects, spiders, ticks, mites, crabs, lobsters, woodlice, centipedes and millipedes are all crustaceans. Underneath a rotting log I recently discovered a crustacean resting right next to a clump of eggs. Not wanting to disturb the creature, I hazarded a guess as to its identity from what I could see. Its form narrowed it down to either a woodlouse (also known as sow bug, pill bug and roly-poly), centipede or millipede. Most centipedes have one pair of legs per body segment, eliminating them from the field of possibilities, for the photographed crustacean has two legs per body segment, as do millipedes and woodlice.
The next clue had to do with the eggs, which I presumed were produced by the creature right next to them. Woodlice have a “marsupium,” a chamber under the thorax which is filled with water in which their (often several hundred) eggs are brooded. Millipedes, on the other hand, lay from ten to three hundred eggs at a time, and deposit them on moist soil. In some species an adult remains to guard the eggs.
I cannot categorically say that today’s subject is a millipede and its eggs, but all signs point to it. If there is a crustacean expert among Naturally Curious readers, please confirm or correct my deduced identification!
American Dog Ticks Can’t Give You Lyme Disease
With the plethora of ticks this spring, it is perhaps comforting to know that not every tick you extract from your body has the potential to give you Lyme disease (or the powassan virus or many of the other diseases carried by Blacklegged Ticks (Ixodes scapularis), also known as Deer Ticks).
The American Dog Tick (Dermacentor variabilis) is the most commonly encountered tick in northern New England. It is found predominantly in areas with little or no tree cover, such as grassy fields and scrubland, as well as along walkways and trails. This species of tick feeds on a variety of hosts, ranging in size from mice to deer and humans. Despite the fact that the bacterium that causes Lyme disease has been found in American Dog Ticks, tests prove that the tick can’t transmit the organism to its hosts. Therefore, the American Dog Tick isn’t involved in the spread of Lyme disease. (It does transmit Rocky Mt. Spotted Fever, however, but there are relatively few cases of it in the Northeast.)
The UNH Extension Service has such a succinct description of this tick’s life cycle that I am sharing it here. It is a “three-host tick,” so named because it must find and feed on an animal three times to complete its two- year life cycle…The dog tick begins life as an egg, one of hundreds laid in a mass on the ground by a female tick. The egg hatches into a larva, which has six legs. The larva remains on the ground in leaf litter, or in low vegetation while waiting for a small mammal (usually a rodent) to brush by. It attaches to the animal and feeds for several days. Then it drops off and molts to the nymph stage, which has eight legs. Again it waits for a host (usually a rodent) to brush by. When that happens, the tick attaches and feeds on it for several days. When fully fed it drops off and molts to the adult stage. Adult ticks wait on shrubs or tall grass and attach to larger mammals such as people, deer, or pets. They also take several days to fully engorge (feed). A female fully engorged with a blood meal can be almost the size of a dime, appearing smooth and shiny. Mating takes place on the host, and when fully fed, the females drop off and lay eggs. The life cycle can be as short as three months. (Photo: American Dog Tick, Dermacentor variabilis)
CDC TICK PREVENTION TIPS:
Use repellents that contain 20% or more DEET (N, N-diethyl-m-toluamide) on exposed skin.
Use products that contain permethrin on clothing. Treat clothing and gear, including boots, pants, socks and tents.
Bathe or shower as soon as possible after coming indoors to wash off and more easily find ticks that are crawling on you.
Check yourself, your kids, and your pets for ticks daily, especially after they spend time outdoors in areas where ticks may be found.
Remove attached ticks as soon as possible. The preferred method of removal is to grasp the tick close to the skin with tweezers or fine-tipped forceps and gently pull upward with constant pressure.
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Black Widow Spiders
Black 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
Several 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
As 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.)
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