No abstract

The mating of the Neotropical lycosid Schizocosa malitiosa is long and complex, involving intense genital stimulation and copulatory courtship. This suggests functions other than just insemination. Previous data indicated that mated females of this species are less sexually receptive than virgins. We hypothesise that copulatory characteristics presented by males during prolonged copulations could be responsible for subsequent female sexual reluctance, and may be selected by cryptic female choice. Our objective was to examine the influence of copulatory behaviour on subsequent female sexual receptivity in S. malitiosa, isolating it from the effects of sperm transfer per se. For this purpose, we obtained males without sperm in their copulatory organs (palpal bulbs), and prevented them from charging their palps by sealing their genital pores immediately after their last moult (treated males). Virgin females were separated into three groups: (i) females exposed once to normal males, (ii) females exposed twice to normal males, and (iii) females exposed first to treated and second to normal males. The results showed that, 3 d after their first mating, females first mated with untreated males were frequently refractory to remating, whereas all those first mated with treated males were receptive. Copulations performed by treated males showed some differences from those performed by normal males, but maintained the basic behavioural pattern with abundant sexual stimulation. The presence of sperm fluids in the female receptacles appears to be the most likely factor generating female remating reluctance. Males may manipulate female responses using receptivity inhibiting substances in their sperm, like those described for insects. Females would first ensure sperm supply, becoming more choosy afterwards. All females, whether mated once or twice, generated similar numbers of progeny, indicating no relationship between number of matings and number of spiderlings.

Allocosa brasiliensis (Petrunkevitch, 1910) is a nocturnal wolf spider inhabitant of coastal dunes. Pitfall-trap data suggested the occurrence of two sympatric and synchronic morphs, with differences in adult size and abdominal design (minor and major morphs). Previous studies performed with the major morph of A. brasiliensis, postulated courtship-role and sexual size dimorphism reversal for this spider. In the present study, we compare data on development and morphology and test reproductive isolation between morphs of A. brasiliensis, with the hypotheses that the two morphs are reproductively isolated and both show courtship-role reversal. As had been reported for the major morph of A. brasiliensis, the minor-morph females approached the burrows of minor-morph males, entered, initiated courtship, and after copulation, males closed their burrows with female cooperation from the inside. Females did not court or copulate with males belonging to the other morph and, in two cases, major-morph females cannibalised minor-morph males. Morphometrical and developmental data showed differences between morphs. The occurrence of copulation only between individuals of the same morph confirm reproductive isolation, supporting the occurrence of two species. Morphological and behavioural data are consistent with courtship-role-reversal hypotheses for the minor morph, constituting the second report in spiders of this atypical behaviour.

Spatial distribution, burrow morphology, phenology, defensive displays and predation of two theraphosid spiders living in meadows were studied in Uruguay. Exhaustive field studies complemented with laboratory observations were carried out. Eupalaestrus weijenberghi occurred throughout the country while Acanthoscurria suina occurred only in the southern half. Both species seemed to be the most abundant theraphosid spiders in Uruguay as they live in the dominant landscape of the country. Burrows from both species showed a similar morphological pattern but a terminal narrow tube was found only in E. weijenberghi. We observed that A. suina always co-occurred with E. weijenberghi but this species frequently occurred in the absence of the former. When cooccurring A. suina showed an aggregated distribution while E. weijenberghi was randomly distributed. A restricted reproductive period was found for both species, mainly between March and April, evidenced by the massive presence of walking adult males and then confirmed by pit-fall traps. Moulting, oviposition and longevity were also studied. Conspicuous species-specific defensive behaviours were displayed by the tarantulas in all cases, when collected. These tarantulas showed spatial co-occurrence and temporal coexistence with the beetle Diloboderus abderus, an important pest of grasslands. Tarantula predation on adult beetles was confirmed, these spiders being one of the few beetle predators. Their maximal efficiency in beetle predation could reach 65 000 prey captured per hectare by month. These polyphagous tarantulas seem to be potential agents for the biological control of beetle pests.

We describe the reproductive biology of seven theraphosid species from Uruguay. Species under study include the Ischnocolinae Oligoxystre argentinense and the Theraphosinae Acanthoscurria suina, Eupalaestrus weijenberghi, Grammostola iheringi, G. mollicoma, Homoeomma uruguayeme and Plesiopelma longisternale. Sexual activity periods were estimated from the occurrence of walking adult males. Sperm induction was described from laboratory studies. Courtship and mating were also described from both field and laboratory observations. Oviposition and egg sac care were studied in the field and laboratory. Two complete cycles including female molting and copulation, egg sac construction and emergence of juveniles were reported for the first time in E. weijenberghi and O. argentinense. The life span of adults was studied and the whole life span was estimated up to 30 years in female G. mollicoma, which seems to be a record for spiders. A com.prehensive review of literature on theraphosid reproductive biology was undertaken. In the discussion, we consider the lengthy and costly sperm induction, the widespread display by body vibrations of courting males, multiple mating strategies of both sexes and the absence of sexual cannibalism.