Macrophytes in tropical shallow lakes: An important food item to benthic entomofauna or an underused resource?

Although macrophytes are known to increase benthic diversity in lakes, the importance of this resource as food for the insects living at the bottom of these ecosystems are still poorly understood. This study assessed the diets of benthic Chironomidae and Campsurus (Ephemeroptera) in two environments: a lake with macrophytes (M+) and another without macrophytes (M?). We expected a differential use of food resources in M+, where plant tissue is particularly important for the aquatic insects’ diet. The diet of 734 individuals from 16 taxa were analyzed. Contrary to expectations, benthic insects consumed low amounts of plant tissue. This finding led us to investigate whether the presence of macrophytes in lakes would indirectly contribute to the benthic insects’ feeding, as more food resources were explored in M+ and a spatial variation of resources intake was observed in this lake, in contrast to the homogeneous feeding in M?. We highlight that macrophytes were responsible for the organic matter build‐up in the sediment, especially at the lake region dominated by these plants, and contributed to increase the deposition of high‐quality amorphous organic matter, which favored taxa in M+ that fed exclusively on this item. The lower diversity of food items exploited in M?, and the Tanypus alga‐based diet in this lake, indicates the low quality of organic resources in its sediment. Although macrophytes were indirectly beneficial for benthic insects’ feeding, we found that this is not an attractive resource for prompt ingestion by most benthic taxa.     

First report that the wasp Gronotoma guamensis (Hymenoptera: Figitidae: Eucoilinae) parasitizes the orchid‐feeding fly Japanagromyza tokunagai in Japan

Compared with mycorrhizal relationships, the relationships between mycoheterotrophic plants and insects have rarely been studied. Here we report a previously unknown tripartite interaction among an endangered mycoheterotrophic orchid, an orchid‐feeding fly, and a parasitoid wasp. The flowers and stems of Eulophia zollingeri were heavily attacked by Japanagromyza tokunagai (Sasakawa) (Diptera: Agromyzidae), and the parasitoid wasp Gronotoma guamensis (Yoshimoto) (Hymenoptera: Figitidae) was reared from these J. tokunagai individuals. Considering the high infestation rate of J. tokunagai, G. guamensis could be important in suppressing the J. tokunagai population, and positively affect the reproductive success of E. zollingeri.