For the last year I have been walking around Las Vegas every day with my camera for exercise and to avoid going mental. Over that time period I have accumulated a collection of lizard photos which I thought would make a nice post. Even though there are lots of little lizards in the Mohave desert (more than 20 species), even in the urban landscape of Las Vegas, most photos are fortuitous since they are so quick and usually small. Lizards and iguanas both belong to the reptile group of vertebrates. The Squamata, or the scaled reptiles, are the largest recent order of reptiles, comprising all lizards and snakes. Iguanas are actually a type of lizard. Therefore, they are not very different from lizards in many aspects. However, they are different from most lizard species in several ways including their colors and the foods they eat. Many lizard species are insectivorous. They like eating insects such as cockroaches, crickets, ants, and beetles. Many lizard species are also omnivorous; they eat just about everything including insects, carrion, small tetrapods, spiders, fruits, and vegetables. Iguanas tend to be herbivores. Of the many species of swifts and spiny lizards, 22 species, some with several subspecies, occur in the United States. Others are found southward through Mexico to northern Panama. In the United States, the lizards of this group are found from southern New York, southern South Dakota and northern Washington in the north, to South Florida, the Gulf States and the Mexican border. Several of the fence lizards (which, because of their rapid movements, are colloquially referred to as “swifts”) are familiar backyard species. Others, among them the bunchgrass lizards and Yarrow’s spiny lizard, are denizens of remote montane fastnesses. Like many other lizards, spiny lizards exhibit metachromatism, which is color change as a function of temperature. When it is cooler, colors are much darker than when the temperature is high. Darker colors increase the amount of heat absorbed from the sun and lighter colors reflect solar radiation.