Black widow
Shiny black with a reddish or yellowish hourglass underneath. Its bite is neurotoxic - get medical help if bitten.
Wildlife / Stinging & biting bugs
Texas's most common "dangerous animals" are small. None of these should keep you inside - just know what to do.
The one that chases
Africanized ('killer') honey bees arrived in Texas in the fall of 1990 and are now established across much of the state. They look like ordinary honey bees, and their sting is no more venomous - but they defend their nest aggressively, in big numbers, and will chase you a long way.
Reddish, mound-building, invasive ants that grab on and sting all at once, leaving an itchy white pustule a day or two later. Stings hurt and can cause allergic reactions in some people (seek care for trouble breathing or widespread hives). Watch where kids play, and treat mounds with approved products.
The striped bark scorpion is the common Texas one. A sting hurts but is rarely dangerous - there are no scorpions in Texas considered lethal to people. They hide in woodpiles, under rocks, and in shoes and attics, so shake out shoes and clothes and seal gaps. (Fun fact: they glow under a UV flashlight.)
Almost all Texas spiders are harmless and helpful. These two are shy and hide in dark, undisturbed spots (closets, garages, woodpiles, boxes), so check shoes, gloves, and stored clothing - and call Poison Control at 1-800-222-1222 if you're bitten.
Shiny black with a reddish or yellowish hourglass underneath. Its bite is neurotoxic - get medical help if bitten.
Golden brown with a violin-shaped mark behind the head. The bite may not hurt at first, but the venom can damage skin over time - get medical help if bitten.
Official sources
Insect and spider information comes from Texas A&M AgriLife Extension and Texas DSHS. For a bite or sting reaction, call the Texas Poison Center Network at 1-800-222-1222.
Caution: This is general information, not medical advice. For a serious reaction, call 911 or Poison Control.