Student Name

Date: 14 Oct. 1997
Time: 1302 CST
Location: Austin College Campus by north entrance to Hughey Gym
Weather: sunny, cool north breeze, approx. 22 C.

General Habitat: Live Oak trees in lawn area

Microhabitat: lowest and outermost leaves on west side Live Oak. Leaves are not in the sun. Galls are growing on the small branches near the leaves.

Species: a wasp similar in appearance to yellowjackets. It was approx. 1.5 cm long with a brownish red body with yellow strips on abdomen.

Species Description: The wasp was black with faint yellow stripes on thorax and abdomen.  It was approximately 1.3 cm long (head to end of abdomen).  The wasp's 2 antennae were about 5 mm long, black and somewhat rounded at the ends. It had 6 legs to walk over gall, and 2 sets of wings to fly from gall to gall.

Behavior: While walking over the gall, the wasp palpated the gall with its antennae. It pressed the ends of the antennae to the gall surface (looked like it was feeling the gall). It then fly to another gall on the tree and repeated the palpation. This was repeated on 4 more galls on this tree before moving to another Live Oak.

Interpretation: It appeared to me that the wasp was "checking out" the gall looking for some special characteristics of the gall. Insect antennae are specialized sensory structures that can perceive odors, wind currents, tastes, touch, and even sound waves. Wasps are known to parasitize other insect larvae by laying their eggs in the host larvae. The developing wasps then feed on the larvae. I think that the wasp was using her antennae to see if the larva inside the gall was appropriate for parasitizing. She might be able to hear or feel the larva moving inside the gall. The larvae in the galls I observed were too young perhaps; so, the wasp flew on. I later cut open one of the galls the wasp palpated and found a small larva (approx. 1 mm). According to Dr. Steve Goldsmith, the larva in the gall is probably from another wasp species (that parasitizes oak trees).

This could be an example of hyperparasitism. The female parasitic wasp has to find larvae of the perfect size to feed her eggs. If the larva were too large or too old, then the host larva would emerge from the gall before the larval wasp was through developing. The female parasitic wasp must have the ability to detect the larva inside the gall (the gall I opened was 2.3 cm in diameter) and then the necessary reproductive structure (ovipositor) to inject her egg into the larva. She needs to visit many galls in a day to find just one larva of the appropriate size. As she will lay multiple eggs most liking, then she will spend many days this fall looking for enough perfect galls.