By Irene Brown
Photos by Gerry Jennings
Views -- Winter 1997
Tree Cricket SongProjecting from the stems and leaves of the tarweed Hemizonia congesta ssp. luzulifolia are hundreds of tiny glands that exude an aromatic resin. Despite its sticky nature, the tarweed is the stage for many summertime dramas, including the courtship and mating of the tree cricket Oecanthus quadripunctatus, abundant on Jasper Ridge during summer of 1995. The summer grassland chorus includes the song of the male tree cricket, Oecanthus quadri-punctatus, a cricket that lives, not in trees, but on the tarweed Hemizonia congesta ssp. luzulifolia. Tree crickets have auditory organs just below the "knees" of their forelegs; the females apparently use these organs to locate singing males, which usually have several females nearby.
CourtingWhen singing, the male lifts his wings up at a 90-degree angle, and rubs enlarged veins in the top wings against the underwings. Raising the wings exposes thoracic pits on his back that are filled with what are believed to be nutritious secretions. A female often approaches a singing male from the back, but the male may turn around and the two may touch antennae. Soon the female climbs on the male's back and begins to eat the secretions in his pits. While she is doing this, the male may continue to sing. He backs up under her until their genitalia are in apposition, and she curves the end of her body downward until mating occurs.
DistractionsAfter mating, the bulbous portion of the spermataphore deposited by the male is visible hanging outside the female's genital opening.
When they separate, the male's task is not over. His sperm-containing packet or spermatophore is too large to fit into her genital opening, and the ampulla, which is the bulbous part containing the sperm, is clearly visible hanging outside her body, held by a thread-like tube. The apparently ever-ravenous female will eat this ampulla--and the sperm in it -- unless the male can distract her. He must occupy her attention long enough for his sperm to travel from the spermatophore to the spermatheca inside of her body where it will fertilize her eggs as they pass down the oviduct.
Often, he sings again and if he is successful, the female climbs on his back and again feeds on the nutritious secretions. He may repeatedly attract her with song and food, but eventually she tires of the food in the pits, or has consumed it all. Then she backs away from the male, loops her head back and down under her body, and devours the ampulla dangling from her genital opening. She may then go on to mate again with the same or different males.
The female tree cricket lays eggs in holes she makes in tarweed stems. As observed by the author, she begins each hole with her sword-like ovipositor, enlarges it with her chewing mouthparts, and then uses the ovipositor to lay an egg in it. Then she starts working on a new hole, approximately 5 mm (.2 in.) from the earlier one.
The following spring, the eggs hatch and young crickets come out of each oviposition scar. The photo shows evenly spaced scars on a tarweed stem.
Views Home | Views Archive | Views Printed Edition Archive