Frequency and consequences of damage to male copulatory organs in a widow spider

Copulatory organ breakage, in which a portion of the male's genitalia breaks off and remains in or attached to the female's genitalia may represent a male strategy of high investment in a single mating. Such a strategy is expected when mating opportunities for males are limited and competition for females is high. We studied costs and benefits for males as a consequence of male organ breakage in the white widow spider (Latrodectus pallidus O. Pickard-Cambridge 1872). In order to estimate the frequency and consequences of such damage we provided each male with four virgin females simultaneously in an outdoors enclosure. We recorded male mating success and loss of the tip of the embolus (the male intromittent organ) inside the female's genitalia for each male. In order to test the effect of the broken tip as a mating plug, we collected females from natural populations and observed the location of embolus tips inside their genitalia. We found that damage to the male organ was frequent but did not necessarily result in male sterility. From the field data, we found that the likelihood of a second embolus tip entering the spermatheca is significantly lower than that of the first tip, suggesting the possibility that the tip functions as a partial mating plug.