PROXIMATE MECHANISMS GOVERNING EGGSAC DISCRIMINATION AND RECOGNITION IN THE WOLF SPIDER Pardosa milvina (ARANEAE: LYCOSIDAE)
Female lycosids carry their egg sacs on their spinnerets until they hatch. Eggsacs weigh 35% of the body mass of the spider and therefore may present a considerable energetic investment to produce as well as transport. Field observations find females occasionally carrying shells, dirt, or other objects on their spinnerets. We investigated the proximate cues governing eggsac recognition and discrimination in the wolf spider Pardosa milvina. We tested the ability of female P. milvina to discriminate egg sacs based on size, texture, and contrast. We also tested P. milvina ability to discriminate between their own or another's egg sac. Spiders were given a choice between two objects. We measured initial time of contact, initial choice, manipulation time, and attachment time. Results found females significantly chose their own eggsac over plastic spheres of equal weight. Spiders showed no preference between round or faceted, black or white, nor large or small artificial eggsacs when given a choice. Spiders were also unable to recognize their own versus another's eggsac. However, females would not reattach their own eggsac once an artificial one had been attached. We conclude P. milvina shows limited eggsac discrimination. Attachment of any object on the spinnerets ceases searching or attachment behavior.