American house spider (Achaearanea tepidariorum), with young. This spider emerges in darkness to produce webs beneath ceilings or in window frames, taking advantage of every angle to set sticky strands where insects may be caught. Then the spider lies in wait on the part of the web that has an extra layer of silk. If large prey gets ensnarled, the spider throws more silk on it and then pulls it up into the web, which is irregular in shape. This spider was formerly assigned to genius Theridion. They can be found throughout the United States and Canada. Ludlow, MA, USA.