Everton Tizo-Pedroso

Mating behaviour and maternal care in the tropical savanna funnel-web spider Aglaoctenus lagotis Holmberg (Araneae: Lycosidae)

Despite their abundance and diversity, Neotropical spiders have been the subject of relatively few studies of behavioural ecology. The sexual behaviour and maternal care of the spider Aglaoctenus lagotis (Lycosidae) is described here. We performed experimental manipulations to test the hypothesis that males are attracted by female cues in the web. Two predictions were tested: (a) webs used by a virgin female will attract more males than webs used by an inseminated female; (b) the main cue in the web is chemical, so webs recently used by virgin females will attract more males than those that are not recently used. Additionally, we tested the hypothesis that maternal care increases offspring survivorship. Results showed that males are attracted by recently used webs (z = 0.0015; p = 0.037; z-test) and webs of virgin females (z = 0.041; p = 0.036, z-test). Male sexual behaviour presented three different categories: court, pre-mate and mate. After the mating, the females built a cocoon that was transported adhered to the spinnerets and held by the last pair of legs. After the hatching of the eggs, the young migrated to the dorsal region of the mothers body for 5 days. During maternal care the mother eliminates a yellowish drop from its oral cavity, which is collected by the young. During the development of the young until adulthood, the offspring that have their mother present in the first stages of life have greater survival compared with those without maternal care. Our results make it possible to perform comparative analyses between a South American Lycosidae species and other species distributed worldwide.

Relation of group size and daily activity patterns to southern lapwing ( Vanellus chilensis ) behaviour

Behavioural patterns of birds commonly vary according to flock size and daily activity pattern. Southern lapwing behaviours and their relation with flock size were studied, as well as the relationship between the frequency of behaviours and the period of the day. Results showed that the proportion of time spent in foraging and vigilance was higher during the morning, when small groups were more common, and decreased from midday on, when group size increased. Maintenance and inactivity (sleeping) behaviours presented the opposite pattern. Correlation between flock size and period of the day, and their similar effects on bird behaviour may be evidence that groups of different sizes could have different functions throughout the day. Our results show that southern lapwings seem to form smaller flocks for feeding in the beginning of the day and larger flocks later for different activities (e.g., maintenance and sleeping). In this sense, it is possible that group size variation throughout the day is related to different demands for specific behaviours (functions) of groups, according to the daily activity patterns of the birds.

Mating behaviour, nympho-imaginal development and description of a new Mesabolivar species (Araneae: Pholcidae) from the Brazilian dry forest

A new species of Mesabolivar is described from Brazilian forests: Mesabolivar delclaroi. The mating behaviour, postembryonic development, number of egg sacs and eggs, birth rate, number of instars, developmental time until adulthood, sex ratio and size of cephalothorax (per instar) were recorded. The sexual behaviour was described and categorized into four steps: courtship, pre-copulation, copulation and post-copulation. After hatching, individuals presented five instars until maturity. The mean number of eggs (42 ± 16.6) and live births (31.5 ± 3.4) of the first egg sac were significantly greater than that of a second one (23.8 ± 3.8, and 19.25 ± 3.9, respectively). The developmental time from birth to adulthood (130.8 ± 9.6 days) did not differ significantly between egg sacs produced (128.61 ± 11.1). The size of the cephalothorax did not differ among adults or between sexes. The sex ratio revealed a shift in favour of females (4: 3).

Capture of large prey and feeding priority in the cooperative pseudoscorpion Paratemnoides nidificator

The social pseudoscorpion Paratemnoides nidificator is a common species in the Brazilian tropical savannah (Cerrado), where colonies are found under the bark of trees. In this environment, colonies hunt for large insects, subduing them by cooperative effort. Small insects are offered as food to nymphs, but large prey tends to be shared by colony members. We investigated the cooperative capture of large prey (Scarabaeidae beetles) by colonies of P. nidificator. During this process, some adults are involved in the immobilization and killing of prey. However, other adults stay as profiteers and do not offer help to subdue the prey. After prey immobilization, pseudoscorpions perform a hierarchical food share in which the attackers begin sucking the prey. These individuals favor the nymphs, offering them the prey and protection during feeding. Profiteer individuals are the last to feed on the carcass. In P. nidificator, obligatory parental care probably favors the evolution of behavioral strategies that prioritize the feeding of juveniles. This mechanism can provide better-quality food for the attackers but offers food to all colony members.

Colony size, habitat structure, and prey size shape the predation ecology of a social pseudoscorpion from a tropical savanna

Predation strategies are driven by habitat structure, prey’s nutritional value, and/or by predator characteristics such as developmental stage. Here, we evaluated the feeding habits of the social pseudoscorpion Paratemnoides nidificator in two areas of a Brazilian Cerrado savanna. These pseudoscorpions live under tree bark trunks of varying sizes; habitat structure could interfere with pseudoscorpion ambushing behavior and prey accessibility. We therefore assessed the hypotheses that (i) small and large colonies of P. nidificator will capture prey of distinct amounts and sizes; (ii) habitat structure will limit the captured prey size; (iii) there will be an age-dependent prey choice in P. nidificator. We evaluated the prey items, colony composition, and habitat structure of pseudoscorpions and determined whether P. nidificator presents age-dependent feeding preferences by offering prey items of different sizes. Colonies with more individuals captured more prey items and those prey presented a wider size variety. P. nidificator can capture a high variety of prey sizes by using openings in tree bark as a trap; however, only tree barks of intermediate size amplitude may be used for trapping most prey. Nymphs showed no preference for prey size, while adults mainly fed on larger ants. Tree bark may play a role as a phenotype extension by easing the process of large prey capture, which is considered a crucial factor for social species. Small prey might be a complementary food resource for nymphs, reducing intraspecific competition and their exposure to larger, dangerous prey.Significance statementHabitat structure and prey’s traits such as size affect the predation strategies of several animals. How these features interfere in the feeding habits and prey accessibility of social arachnids is a matter of question. We showed that habitat structure and colony size drive the prey size preference of a social pseudoscorpion. Paratemnoides nidificator lives under tree trunk barks that vary in size, depth, and shape. The tree bark openings may play a crucial role by easing the capture process of different prey sizes, including large prey, which is considered a crucial factor for social species. According to the prey size hypothesis, social species require, collectively, higher amounts of food energy. Thus, we propose that the bark openings are related to the evolution of P. nidificator’s social behavior as they potentially allow the capture of larger and more nutritious prey.