História natural da interação entre o parasitoide Eruga UnilabianaPádua & Sobczak, 2018 (Hymenoptera, Ichneumonidae, Pimplinae) e duas aranhas hospedeiras, na serra de Baturité, Ce, Brasil

Abstract

Wasps of the Polysphincta genus-group are currently the only Pimpliinae (Hymenoptera: Ichneumonidae) known as Koinobiont ectoparasitoids of spiders. They exhibit a variety of host exploration strategies, including the behavioral manipulation of hosts so that they build webs with structures that provide protection to their pupae against natural enemies and abiotic factors, however, there is a lack of knowledge of natural history of many interactions already registered, especially where the data point to the occurrence of behavioral manipulation of hosts. This work focuses on the recently described parasitoid of the Polysphincta group, Eruga unilabiana Pádua & Sobczak, 2018, which is associated with the spider, Sphecozone sp. (Linyphiidae) in the mountains of Baturité, Ceará, Brazil. n the first chapter, (i) we (i) report the interaction between the parasitoid wasp Eruga unilabiana and the spider Eurymorion sp., for the first time, (ii) describe of the normal and cocoon webs of Eurymorion sp. induced by larvae of the penultimate instar of E. unilabiana, (iii) quantified the differences between the structures of normal and cocoon webs of Eurymorion sp. and Sphecozone sp. spiders and (iv) we describe the behavior of two spiders under influence of the larvae of the penultimate instar of E. unilabiana. We found that modified webs constructed by individuals of Eurymorion sp. have more protective and stable characteristics than normal webs and are structurally similar to individuals of Sphecozone sp. they do when they are manipulated by the same parasitoid. Sheet areas and interception thread length of the modified webs were significantly smaller when compared to normal webs. Individuals of the two species of spiders are induced to abandon their normal webs to build modified web from scratch. Both (1) the abandonment of the normal web to build the cocoon web from scratch and (2) the characteristics of the webs of the modified web probably guarantee greater chances of survival for E. unilabiana pupae. In the second chapter, (i) we describe the morphology, behavior and development of the immature stages of E. unilabiana, (ii) we investigate the frequency of parasitism of E. unilabiana in the population of Sphecozone sp. and Eurymorion sp., (iii) we evaluated the possible selection of host size at the time of oviposition and, (iv) we report the attack of an adult female of E. unilabiana on an individual of Eurymorion sp. registered in the field. We found that the egg is a white cylindrical mass that is usually positioned across the anterior portion of the spider's abdomen. First-instar larvae hatch from the egg three days9 after being deposited in the spider's abdomen and do not have segmentation in the body or structures that appear in later stages. Second instar larvae present segmentation in the body and induce spiders to build a modified web to pupae protection. Third-instar larvae have eight pairs of retractable dorsal tubercles with tiny hooks, two pairs of ventral protuberances and, before killing and discarding the spider's remains, they invert the spider's position on the web sheet in order to build the cocoon on this sheet. The cocoon is constructed in the center of the modified web sheet and the silk used to form the cocoon's outer lining is produced in the anal segment. The adult wasp hatch on average 10 days after the beginning of the pupae stage with release of meconium. The frequency of parasitism in the population of Sphecozone sp. and Eurymorion sp., is low and was higher in intermediate size and female individuals of both spider species. With these results, we found that the immature stages of E. unilabiana present not only the same basic morphological and behavioral characteristics already known for species within the Polysphinctas group, but also new ones adjusted to the ecology and behavior of the two hosts spiders. The production of silk in the anal segment for the construction of the cocoon is also the first recorded in Ichneumonidae wasps.