California Gallfly – Andricus californicus

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California Gallfly (Andricus californicus)

Latin Name: Andricus quercuscalifornicus

Common Name: California Gall Wasp or Gallfly

Appearance: 

Egg:

  • Eggs are laid within or on twigs.

Larva/nymphs:

  • The larvae/nymphs are found inside the gallbladder.

Adult:

  • Adults are 3-5mm long.
  • This wasp is tiny, brown, and has transparent wings.
  • The wings of a bird extend beyond the abdomen.
  • Filiform and roughly the same length as the legs, the antennae are filiform.
  • Only parthenogenetic females have been identified.

Hosts plants: White Oaks

Territory: 

It may be found throughout the United States, including Washington, Oregon, California, and northern Mexico.

Damages caused by California Gall Wasp:

Female gall wasps or midges lay eggs in or on plant tissue as adults. The formation of galls is poorly understood; however, they usually appear several weeks or months after the eggs hatch. Larvae feed beneath the plant tissue, and their secretions cause aberrant cell development in the plant. Galls can sometimes cause slight harm to leaves and stems. Galls and associated wasps aren’t a severe concern for oaks, but they are food for other creatures like birds and insects.

Gall maker’s description:

Galls are tree growths that wasps, flies have taken over, and other insects to create a casing of plant tissue that protects and supports the gall maker’s growing young. Gall-maker insects include a variety of wasps, flies, and a few aphids and mites. Most growths, except some twig and stem galls, do not affect healthy trees. Galls can develop on the leaves, bark, flowers, buds, or roots of plants. Over half of these fascinating critters are attracted to oak trees.

 

Life History and Habits: 

Andricus quercuscalifornicus may infect and live in the galls of a wide range of oak species; however, they are most commonly seen on Valley Oaks. The adult female uses her ovipositor to deposit eggs in the cambium layer of oak twigs during the fall. The eggs are laid on the twig during the winter and hatch in the spring, generally in early April. The resultant larvae cause galls nearly instantly, and they can appear to inflate onto the tree practically overnight. Most parasitoids penetrate the gall at this phase while still soft and tiny enough for their egg to reach.