Ten new species of Myrsidea Waterston, 1915 parasitic on members of the avian families Formicariidae, Thraupidae, Tyrannidae, Troglodytidae and Icteridae are described herein. They and their type hosts are M. isacantha sp. n. ex Chamaeza nobilis Gould, M. circumsternata sp. n. ex Formicarius colma Boddaert (Formicariidae); M. cacioppoi sp. n. ex Lanio fulvus (Boddaert), M. brasiliensis sp. n. ex Tangara chilensis (Vigors), M. saviti sp. n. ex Tangara schrankii (Spix) (Thraupidae), M. rodriguesae sp. n. ex Cnipodectes subbrunneus (Sclater), M. cnemotriccola sp. n. ex Cnemotriccus fuscatus (Wied-Neuwied), M. lathrotriccola sp. n. ex Lathrotriccus euleri (Cabanis) (Tyrannidae), M. faccioae sp. n. ex Cyphorhinus arada transfluvialis (Todd) (Troglodytidae), and M. lampropsaricola sp. n. ex Lampropsar tanagrinus (Spix) (Icteridae). Among these are two new Myrsidea species described from the avian family Formicariidae, which previously had only a single described Myrsidea species, and a new host record for M. cinnamomei Dalgleish et Price, 2005 ex Attila citriniventris Sclater. Analysis of mitochondrial cytochrome oxidase I sequences for these and other neotropical Myrsidea species provides an assessment of their phylogenetic relationships and indicates that all of these newly described species are genetically distinct. We also put these descriptions into context by estimating the potential number of unnamed Myrsidea species in Brazil, given the known diversity of potential hosts and typical levels of host specificity for Myrsidea species. Our estimate indicates that Brazilian Myrsidea species diversity is likely more than an order of magnitude greater than the number of described Myrsidea species known from Brazil, highlighting the need for future work on this megadiverse ectoparasite genus.
The paper reviews existing data on the food quality of cereal aphids for generalist predators. Data are presented for spiders, harvestmen, carabid and staphylinid beetles, cockroaches, ants and one species of bird. All results agree that cereal aphids are low-quality food compared to alternative prey types (in most studies fruit flies). This is associated both with a low consumption capacity for aphids and a low utilization efficiency of the aphid food. A pure aphid diet allows full juvenile development in only a few species. Aphids as part of mixed diets can have negative, neutral or positive effects, which depends on the quality of the remaining diet. The low consumption capacity for aphids is due to the development of a specific feeding aversion. Genetic variation in the ability to tolerate aphids has been documented, indicating that predators may be able to adapt to a higher proportion of aphids in the diet in areas where outbreaks are frequent. A consequence of these findings is that predator populations rely on alternative prey (e.g. Collembola and Diptera) for maintenance and reproduction, and are probably unable to benefit nutritionally from an aphid outbreak. The low food quality of aphids to generalist predators explains why generalist and specialist predators have widely different roles in aphid biocontrol, but does not rule out that under some conditions the generalists may be able to inhibit aphid population growth sufficiently to prevent an outbreak, as field experiments have indicated. Simulation modelling shows that a low consumption capacity for aphids has little influence on the ability to prevent aphid population increase at low aphid immigration rates, but a great influence at high aphid immigration rates. Modelling also indicates that there may be an optimal availability of high-quality alternative prey that maximizes the impact of generalist predators on aphid population growth.