Virtually all of the major bedding manufacturers have either gone totally to that design, abandoning the two-sided design, or have allotted a healthy percentage of their products to it. mattress construction appears to be a one-sided issue
Bird Spider and Bird Eating Spiders. The Chinese bird spiders are venomous spiders capable of delivering a rather dangerous bite. Their LD50-value is low and in the same range as many loxosceles species (brown recluse spiders). Chinese bird spiders are tarantulas, just like the goliath bird eating spider is a tarantula. Chinese bird spiders are widely distributed in Asia and are abundant in Southern China.
Brown spiders are present in the Midwest and South Central United States, not in the coastal and Canadian border states, except when imported on clothing or luggage. Widow spiders are present throughout the United States. Although some people consider tarantulas dangerous, their bites do not seriously harm people. Spider bites cause fewer than three deaths a year in the United States, usually in children.