Eleven species of billbugs (Coleoptera: Dryophthoridae: Sphenophorus spp. Schönherr) infest managed turfgrass in North America. However, the regional variation in species composition remains unresolved and the seasonal phenology of several species has not been well documented. The latter gap is largely due to the inability to identify the larval stage to species-a confounding problem with several sympatric insect species. We used field trapping (adults) and soil sampling (larvae and pupae) surveys along with a DNA-based life-stage association to characterize the biology of billbugs associated with turfgrass in the Midwestern United States. Pitfall trapping at four locations in Indiana revealed four billbug species: S. venatus Say, S. parvulus Gyllenhaal, S. minimus Hart, and S. inaequalis Say. Sphenophorus venatus was the most abundant species on warm-season turfgrass while S. parvulus was most abundant on cool-season turfgrass. Investigation of S. venatus seasonal biology revealed two overwintered life stages-larva and adult-which resulted in two overlapping cohorts and two larval generations. Degree-day models describing S. venatus activity were more accurate for first-generation adults and larvae than for overwintering life stages. Maximum-likelihood analyses provided the first molecular species identification of billbug larvae and direct evidence that S. venatus larvae are capable of overwintering above 40°N latitude. Findings clarify the utility of molecular markers (CO1, 18S, and ITS2) for describing billbug larval population dynamics and seasonal phenology in regions where several sympatric billbug species occur. These results support the development of sustainable management strategies based on billbug seasonal phenology in different regions of North America.
Insect chemical ecology (ICE) evolved as a discipline concerned with plant–insect interactions, and also with a strong focus on intraspecific pheromone-mediated communication. Progress in this field has rendered a more complete picture of how insects exploit chemical information in their surroundings in order to survive and navigate their world successfully. Simultaneously, this progress has prompted new research questions about the evolution of insect chemosensation and related ecological adaptations, molecular mechanisms that mediate commonly observed behaviors, and the consequences of chemically mediated interactions in different ecosystems. Themed meetings, workshops, and summer schools are ideal platforms for discussing scientific advancements as well as identifying gaps and challenges within the discipline. From the 11th to the 22nd of June 2018, the 11th annual PhD course in ICE was held at the Swedish University of Agricultural Sciences (SLU) Alnarp, Sweden. The course was made up of 35 student participants from 22 nationalities (Fig. 1a) as well as 32 lecturers. Lectures and laboratory demonstrations were supported by literature seminars, and four broad research areas were covered: (1) multitrophic interactions and plant defenses, (2) chemical communication focusing on odor sensing, processing, and behavior, (3) disease vectors, and (4) applied aspects of basic ICE research in agriculture. This particular article contains a summary and brief synthesis of these main emergent themes and discussions from the ICE 2018 course. In addition, we also provide suggestions on teaching the next generation of ICE scientists, especially during unprecedented global situations.
Beetles in the genus Sphenophorus Schönherr, or billbugs, potentially utilize both volatile and non-volatile behavior-modifying chemical signals. These insects are widely distributed across North America, often occurring in multi-species assemblages in grasses. However, details about their host- and mate-finding behavior are poorly understood. This study tested the hypothesis that volatile organic compounds from host-plants and conspecifics direct the dispersal behavior of hunting billbug S. venatus Say. Further, we characterized the cuticular hydrocarbon profiles of two widespread pest species, S. venatus and bluegrass billbug S. parvulus Gyllenhaal, to assess the potential role of contact pheromones in mate-recognition. In Y-tube olfactometer bioassays, S. venatus males were attracted to a combination of conspecifics and Cynodon dactylon host-plant material, as well as C. dactylon plant material alone. S. venatus females were attracted to a combination of male conspecifics and host-plants but were also attracted to male conspecifics alone. Field evaluation of a putative male-produced aggregation pheromone, 2-methyl-4-octanol, identified from two congeners, S. levis Vaurie and S. incurrens Gyllenhaal, did not support the hypothesis that S. venatus and S. parvulus were also attracted to this compound. Gas chromatography-mass spectrometry analysis of S. venatus and S. parvulus whole-body cuticular extracts indicated a series of hydrocarbons with qualitative and quantitative interspecific variation in addition to intraspecific quantitative variation between males and females. This study provides the first evidence that S. venatus orients toward host- and insect-derived volatile organic compounds and substantiates the presence of species-specific cuticular hydrocarbons that could serve as contact pheromones for sympatric Sphenophorus species.
The family Nitidulidae is known for its diverse life histories, with some species considered economically detrimental pests, while others perform critical ecosystem functions. Despite this, their evolutionary relationships still lack support and understanding. A robust phylogenetic hypothesis and revised taxonomic classification for this group, particularly the subfamily Carpophilinae, could help delineate key lineages for assessing the evolution of both beneficial and pestiferous traits. The most complete molecular phylogeny of Carpophilinae to date, based on 37 ingroup taxa, covering four of the six recognized genera, is presented. Six genetic loci were used (16S, 18S, 28S, COI, H3 and ITS2), providing a total of 3500 bp of data. These data were generated using a novel method discussed here: wide-seq. Wide-seq utilizes next-generation sequencing platforms to generate data for specific loci that overlap with traditional Sanger sequences for the group. Carpophilinae recover as a well-supported clade with respect to the outgroup taxa. The genera Nitops, Urophorus and Caplothorax stat. nov. recover as monophyletic with high support. Caplothorax is formally given generic rank with a redescription and diagnosis. Anthophilous behaviour is coded for all taxa and an ancestral state reconstruction is performed, predicting multiple origins of this behaviour within Carpophilinae.
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