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The generalist predator Orius similis plays a crucial role in controlling the pests Frankliniella occidentalis (Pergande) and Tetranychus urticae Koch. To assess the effectiveness of O. similis in controlling these pests in bean field, we conducted field surveys and used DNA molecular analysis to quantitatively measure the levels of predation on each prey. Field surveys conducted from June 18 to August 7, 2021, showed a linear increase in the population densities of O. similis, F. occidentalis, and T. urticae. The population density of F. occidentalis and T. urticae peaked on July 16, whereas that of O. similis peaked on July 23. The highest positive rate for F. occidentalis and T. urticae was observed on July 23 and 16, respectively. The positive detection rate to F. occidentalis was significantly higher than that of T. urticae (t = 7.659, df = 14, P < 0.0001). The DNA half-lives of F. occidentalis and T. urticae were estimated at 4.44 and 2.60 h, respectively, based on the positive detection rates of both preys during the digestion time in O. similis. These results suggest that molecular intestinal content analysis can be effectively used to quantitatively evaluate the control effect of O. similis on F. occidentalis and T. urticae. [ABSTRACT FROM AUTHOR]

Access to surface water is crucial for herbivores in arid ecosystems. Here, we build a game-theoretical model, based on an evolutionary algorithm, to study the influence of ecological factors on the temporal patterns of presence at waterholes in the herbivore community. In this model, we incorporate the specific features of arid environments, namely, the important hydric losses endured by individuals exposed during the warmest hours of the day, and competition for access to water, both within and between species. We also consider the presence of ambushing predators around waterholes, particularly during dark hours. In response to this predation regime, our model predicts a strong aggregative tendency in herbivores. The number of groups, however, is variable, as well as the time these groups choose to attend the waterhole, even if the total number of individuals is fixed. The reason is a multiplicity of possible evolutionarily stable strategies, corresponding to different responses to the trade-off between the advantages of grouping, in terms of risk dilution, and its costs, in terms of increased competition. This variety of possible behavioural responses affects, in turn, the moments when the waterhole is occupied, and the moments when the different species meet each other. In general, herbivores also respond to predation threat by avoiding coming to waterholes after dusk. However, the cumulative effects of a relatively high level of predation during the day and a high level of interspecific competition for access to water may induce an important presence of herbivores at the waterhole at night. Our predictions are discussed in the light of existing empirical studies. [ABSTRACT FROM AUTHOR]

Polymorphism in warning coloration is puzzling because positive frequency-dependent selection by predators is expected to promote monomorphic warning signals in defended prey., We studied predation on the warning-coloured wood tiger moth ( Parasemia plantaginis) by using artificial prey resembling white and yellow male colour morphs in five separate populations with different naturally occurring morph frequencies., We tested whether predation favours one of the colour morphs over the other and whether that is influenced either by local, natural colour morph frequencies or predator community composition., We found that yellow specimens were attacked less than white ones regardless of the local frequency of the morphs indicating frequency-independent selection, but predation did depend on predator community composition: yellows suffered less attacks when Paridae were abundant, whereas whites suffered less attacks when Prunellidae were abundant., Our results suggest that spatial heterogeneity in predator community composition can generate a geographical mosaic of selection facilitating the evolution of polymorphic warning signals. This is the first time this mechanism gains experimental support. Altogether, this study sheds light on the evolution of adaptive coloration in heterogeneous environments. [ABSTRACT FROM AUTHOR]

1 Populations of an indigenous longhorn beetle, the red oak borer Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae), recently reached epidemic levels in the Ozark National Forests of Arkansas and Missouri, resulting in extensive tree mortality. 2 The factors regulating E. rufulus populations are largely unknown. Ants appear to be the most abundant potential predators in the Ozarks and have been shown to play a role in regulating populations of other forest insects. 3 The main objective of the present study was to determine whether ants are predators of early E. rufulus life stages by direct observation of E. rufulus eggs artificially placed on tree trunks and by development of molecular tools to detect E. rufulus DNA within ant gut contents. 4 Three hundred and eighty E. rufulus eggs were applied to ten northern red oaks. Ants ate or carried away 72% of the eggs within 1 h. Camponotus pennsylvanicus (De Geer) and Aphaenogaster tennesseensis (Mayr) were identified as the two primary ant species observed in the study. 5 A portion of the mitochondrial 16S rRNA gene of E. rufulus was sequenced and polymerase chain reaction primers were developed to detect E. rufulus DNA in the guts of C. pennsylvanicus. Enaphalodes rufulus DNA persisted in ant gut contents for at least 24 h after ingestion under laboratory conditions, and E. rufulus DNA was detected in field-collected ant populations, suggesting the natural occurrence of ant predation on this insect. [ABSTRACT FROM AUTHOR]

1. The relative importance of host-plants and predators in the population dynamics of herbivorous insects, and the frequency and intensity of inter-specific competition among herbivores, have both been intensively studied and debated. The joint effects of bottom-up, top-down, and within-trophic level interactions, however, have rarely been integrated in a single system. 2. I studied the dynamics of the cactus bug ( Narnia pallidicornis), a specialist feeder on tree cholla cactus ( Opuntia imbricata), in response to variable host-plant quality, spider predation, and interactions with cactus-feeding beetles ( Moneilema appressum). Previous work suggests that cactus reproductive effort (the proportion of meristems allocated to reproduction) is an important component of host-plant quality for Narnia. I conducted a 2-year field experiment to test the hypotheses that Narnia abundance is positively related to host-plant reproductive effort, and that interactions with predators and putative competitors alter the shape of this relationship. 3. I found strong support for the first prediction (positive Narnia–plant quality relationship) in both years, but neither predator removal nor beetle exclusion had detectable effects on this relationship in either year. I conclude that the dynamics of this insect herbivore are driven predominantly from the bottom-up, and that available data from this work and from previous studies are too variable to permit broad generalisations for the combined effects of host-plants, predation, and competition on herbivore dynamics. [ABSTRACT FROM AUTHOR]