After the colors in the landscape fade under clear skies and 100 degree temperatures, rain quickly brings fresh vigor to humans, plants and animals. The straw-colored grass soon has hearts of green -- our native grasses have the ability to green up within hours of a rain. Within 48 hours a grass leaf blade can grow 2 inches.
Little piles of dark earthworm castings sprinkle the soil after a rain. During dry spells earthworms wait, deep in the soil, encased in a shell made of their mucous and the dirt. After a rain, they feast on decaying organic material during the time of moisture and void the processed material, castings, on the surface.
Cryptogams are plants and fungi that do not reproduce by seeds. After a rain, black cryptogamic crusts turn green. The blue-green algae in cryptogams take nitrogen out of the air and transfers it to the soil -- they are the most important source of fertility in arid soils.
Grassland termites swarm by the billions soon after a rain. Small holes with little cones of soil appear near the castings and cryptogamic crusts, but are not the exit holes for the termites. The little cones are the exit holes for Velvet mites.These plush red arachnids are found in soil litter. They are often mistaken for baby tarantulas, but they’re not. Some kids call them Santa Claus bugs because of their cute cuddly appearance. They’re usually referred to as rain bugs.
Little information has been published about the natural history of the rain bugs. Rain bugs eat grassland termites. After the sexually mature termites have flown, they come back to earth and mate. The females immediately dig back underground, but the males are no longer useful except as a major food source not only for the rain bugs, but also toads. Both the rainbugs and toads only eat once a year -- stuffing themselves on termites! The rainbugs prefer to eat the termites on sunny mornings, but the toads are not as choosy, and rainbugs are always on their menu.
Rainbugs live in 6-12 inch non-branching tunnels in the soil. The tunnels go straight down. The tunnels are closed except during their emergence and during succeeding rains, when the rainbugs remain at the burrow entrance. Keeping the burrows closed keeps the rainbugs from drying out. They don’t return to the burrow they left, but dig a new one. The little arachnids move up and down in the burrow according to the seasons – the deepest during the summer, near the surface in the winter, and halfway down during spring and fall.
Rainbugs lay their eggs in clusters in the burrow, a full three months after mating. After five weeks, the eggs hatch, and then the newborn rainbugs crawl to the surface.
At mating time 3-7 rainbugs gather around one other rainbug and march around it in circles, waving their front four legs. They move their legs rapidly and continually, as they circle. Photographs of the circling rainbugs have revealed that there is a circle of silk line. Spermatophores are attached to the silkline, and the males chase the females over the line to accomplish fertilization.
One rainbug researcher wondered whether the rainbugs red color indicates that it tastes terrible. Investigation confirmed that, as in other places in nature, red is protection that indicates a foul-tasting insect.
Nature Notes is sponsored by the Dixon Water Foundation and is produced by KRTS Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas. This episode was written by Burr Williams of the Sibley Nature Center.
