No abstract

The genus Holopothrips represents the main Neotropical group of thrips associated with plant galls, and several of the 36 currently described species are known to induce or invade galls of other organisms. The existence of several Holopothrips specimens in collections that do not belong to any of the already described species, allied to the absence of basic biological information for several species, such as host plants and habit, shows that the current knowledge on the genus is severely lacking. Here we start addressing these problems, by describing 24 new species: H. acrioris, H. atlanticus, H. bicolor, H. brevicapitatum, H. cardosoi, H. curiosus, H. flavisetis, H. graziae, H. inconspicuus, H. infestans, H. irregularis, H. johanseni, H. kaminskii, H. longihamus, H. longisetus, H. magnus, H. maiae, H. nigrisetis, H. nigrum, H. punctatus, H. reticulatus, H. singularis, H. spermathecus, H. varicolor. This study also includes information on galls for several species; an updated and illustrated key to species; and comments on the morphological diversity of the group. With that, we hope to lay the taxonomic and morphological bases for future studies in this group, focusing on its diversity, ecology and phylogenetic relationships.

Several stink bugs in the subfamily Pentatominae are crop pests or have the potential to damage plants of economic importance. In the Brazilian state of Rio Grande do Sul, where agriculture plays a major role in the economy, the knowledge about pest stink bugs is fragmented and, in some instances, outdated. This work provides a summary of Pentatominae species recorded in Rio Grande do Sul feeding on the four most important grain crops for the state, i.e. soybean, rice, maize, and wheat, plus canola, an emerging crop. This survey is enhanced with new records from scientific collections, a short diagnosis for each species, distribution maps, an identification key, and carefully illustrated to allow for species recognition in the field. With this work, we aim to reunite the scattered knowledge of the group in one single revision, and provide a useful tool for identifying the pest stink bugs of Rio Grande do Sul.

Holopothrips molzi sp. n. (Thysanoptera: Phlaeothripidae) is described from southern Brazil inducing leaf galls on Myrcia guianensis (Myrtaceae). Field observations revealed that the numbers of this thrips were highly variable within galls, and two other insect species were recorded living in these galls: Myrciathrips variabilis Cavalleri et al. (Phlaeothripidae) and an eulophid wasp (Hymenoptera). We investigated here if morphological traits of leaf and gall and abundance of the invader thrips were correlated with the gall inducer's abundance. In order to determine the feeding habit and behaviour of M. variabilis and its interactions with the gall inducer we performed observations ad libitum and attack simulation tests on both thrips species to observe their response to possible invaders. Our results showed that leaf size is not related to H. molzi abundance, and gall size is relevant only when total numbers of both thrips species are considered. Myrciathrips variabilis was observed feeding on gall tissues, and no direct antagonistic interactions between the two thrips were recorded. The results of the behavioural tests simulating attacks were remarkably different in the two thrips species, indicating different strategies when threatened or disturbed. The interaction between the two thrips species is probably a case of inquilinism.

Holopothrips is a diverse group of thrips associated to galls in the Neotropics, with a variety of host plants and wide morphological diversity. Relationships to other Neotropical groups have been proposed, but are still untested, and the monophyly of the genus remains doubtful. Here, we perform a phylogenetic analysis of Holopothrips, based on morphological characters. A total of 87 species were included in the matrix and eight analyses were carried out, but all of them failed to recover Holopothrips as a monophyletic grouping. Bremer and Bootstrap support values were low, and the topologies varied among all analyses, with uncertain internal relations for the ingroup. These results indicate that the relationships for Holopothrips species, and the proposed related genera, are more complex than previously reported; and morphological characters may not be enough to recover the evolutionary story within this group. We also discuss the influences of different character coding, continuous characters and weighting schemes in our results.