This week’s BOTW features a few oak galls and a grape gall. Remember, of the 2,000-plus kinds of galls found on North American plants, 800 different kinds form on oaks. Cynipid wasps, which mainly target stems and leaves, are very big players in the oak gall game. The galls caused by some Cynipid wasps are very high in tannin/gallotannin, giving them the bitter taste that gave rise to their name, gall.
Galls are defined as abnormal growths on plants (and animals). They can be caused by friction, as when two plants rub against each other for a long period of time, but they are also precipitated by a variety of biological agents including viruses, mites, nematodes, and fungi (which cause witch’s broom). The vast majority of galls in the U.S. are made by insects in just a few groups of flies (gall midge larvae), and wasps (1/3 of galls are caused by tiny Cynipid wasps).
Cuckoo Wasps are found worldwide except in Antarctica. There are about 230 species north of the Rio Grande, and California is especially cuckoo-wasp-rich. The name refers to their habit of depositing their eggs in other insects’ nests; a strategy practiced by birds like the Old World Cuckoos. The larvae of some species of cuckoo wasps feed on the larvae of the nest-builder, usually another wasp, a bee, a silk moth or a walking stick.
Darkling beetles are small-to-medium-sized, dark, slow-moving beetles. Their elytra are often grooved and/or pitted. Both the adults and larvae are nocturnal scavengers on “dead” material like clothing, rugs, stored foods, and plant and insect collections as well as on rotting wood and fungi. There are about 1,200 species of darkling beetles in North America mostly in the West.
Tiger moths are in the Family Arctiidae, a diverse group with worldwide distribution and 250 species in North America. Arctiid moths are unusual in that they have an organ on their thorax that vibrates to produce ultrasonic sound. They “vocalize” to attract mates and to defend against predators. Many of their caterpillars are fuzzy, earning a group name of woolly bears or woolly worms.
Ambush bugs wear the name “bug” proudly and legitimately, which means that their forewings have two different textures—the proximal half (closest to the body) is leathery, and the distal half (away from the body) is membranous, like a fly’s wing. They have a “beak” for sucking, and this beak is tucked in under its “chin.” What they do well is predation, and to that end, ambush bugs are equipped with a few adaptations that allow them to prey on insects much, much larger than they are:
Black Saddlebags are known for spending the greater part of each day in flight, rarely perching. They are strong flyers, and their flight is described as a “flap-glide” that may reach 17 mph. They patrol fields and pond edges for their prey—soft bodied flying insects like moths and mosquitoes which they eat on the wing—and large swarms of feeding males have been reported. The dark patches/bands on the wide hind wings shade their abdomens on sunny days.
This “Hummingbird Moths” in the genus Hemaris; their genus name may come from the Greek hemara meaning a day in reference to their day-time habits. They are also called Clear-winged Moths, a common name they share with yet another very spiffy but unrelated group of moths. Their range extends from the Pacific Northwest, east and south through most of the U.S. Adults hover in front of the flowers of fields, gardens and edges to sip their nectar.
Looking like dark watermelon seeds, mobs of whirligig beetles scoot across the still waters of ponds, lakes, streams and rivers. Their basic design is a short antennae, elytra that end before the abdomen does, the ability to secrete a smelly substance that deters predators, and a shiny, black finish. They row with their flattened and fringed middle and hind pairs of legs, and they hold their front pair of legs forward, ready to grasp their prey.
Water Sow Bugs (WSBs) have three body segments— a cephalothorax (combined head and first segment of the thorax), a thorax (7 segments), and an abdomen (everything after that). WSBs have 7 pairs of legs, one per segment of the thorax. The first pair is adapted for holding; the rest of these boots are made for walking. To that, add 6 short appendages on the underside of the abdomen, the final pair of which looks like two tails. WSBs are flattened for crawling under stuff, drab in color, and about ½” long. Look for WSBs under dead leaves and debris in shallow water.