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Diversidad y control biológico de insectos - CyberTesis UACh ...

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prey attacked (Larochelle, 1990; Smith et al., 2004). In mid spring and early summer,<br />

Dalaca sp. larvae reach 5-6 cm long and 580 ± 167 miligrams (Devotto, unpub. data). This<br />

body size is 3 to 4-fold the body size of the most abundant species <strong>de</strong>tected in our study. In<br />

our dry pitfall traps, occasionally some Dalaca sp. larvae were caught. Carabid beetles<br />

readily preyed on them, but only when their numbers were much higher than Dalaca sp.<br />

larvae. At field, it is likely that the very active and strong Dalaca sp. larvae could escape<br />

from predation. If some species of the carabid assemblage do prey on mature larvae,<br />

potential candidates must be the large carabids such as Calosoma vagans and Ceroglossus<br />

chilensis, species that emerge latter in the season. The first species belongs to a gen<strong>de</strong>r<br />

commonly called “caterpillar hunters” because Calosoma tend to prey on lepidopteran<br />

larvae (French et al. 2004;, Toft and Bil<strong>de</strong>, 2002). Unfortunately, prey range of these<br />

species remains unknown, especially on C. vagans, which has a pre-oral digestión system.<br />

On the other hand, eggs and neonate larvae are abundant resources for several months in<br />

the pastures. The Dalaca sp. females bear up to 2000 eggs and they drop them over the<br />

pastures in a no directed way (Cisternas, personal comm.). In the Dalaca sp. breeding<br />

period, hundreds of eggs can be found at random on weed leaves, in the grass and at the soil<br />

surface, where they are exposed to predation, as well as neonate larvae. The potential role<br />

of carabids and spi<strong>de</strong>rs as predators of eggs and neonate larvae must not be dismissed and<br />

warrants further research.<br />

Spi<strong>de</strong>rs<br />

The lack of high numbers did not allow <strong>de</strong>tecting differences between treatments<br />

immediately after spraying. By day 30, lycosid and gnaphosid spi<strong>de</strong>rs increased in all plots,<br />

but the increase was higher in <strong>control</strong> and B. bassiana plots. The spi<strong>de</strong>r numbers kept<br />

growing by day 60 in the lambda-cyhalothrin plots, but in the <strong>control</strong> and B. bassiana plots<br />

the spi<strong>de</strong>r numbers were similar (lycosids) and lower (gnaphosids) than the spi<strong>de</strong>r numbers<br />

in the same plots in the previous sampling date. We did not distinguish spi<strong>de</strong>rs by sex nor<br />

did we record the size of the spi<strong>de</strong>rs trapped, but the authors noted females bearing egg sacs<br />

and spi<strong>de</strong>rlings only late in the sampling period, therefore the increase in insectici<strong>de</strong> plots<br />

by day 60 could be a re-distribution of adults rather than recruitment of new individuals.<br />

The size plot must not be an obstacle to cursorial movement of spi<strong>de</strong>rs, though they can<br />

cover consi<strong>de</strong>rable daily distances (Kiss and Samu, 2000). These findings confirmed that<br />

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