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Animals have evolved to overcome the consistent hardships encountered within their environment including biotic factors such as pathogens and predators as well as abiotic factors including temperature and rainfall. Diapause is one such program animals have developed to overcome adverse winter or summer conditions. Typically, reliable environmental cues trigger this alternative developmental pathway causing an extensive shift in both behavior and physiology. These changes permit diapausing organisms to over-winter or -summer successfully and restart spring populations more rapidly upon the return of favorable conditions. Many studies have investigated the environmental cues that initiate diapause and mechanisms underlying this alternative developmental pathway. To better understand diapause in the northern house mosquito, Culex pipiens, we utilized next generation sequencing to investigate the microbiota associated with diapause, in addition to other molecular and physiological techniques to better understand microbiota-diapause interactions and characterize temperature related immune response changes during diapause.Midgut microbial communities were identified with 16s rRNA amplicon sequencing within diapausing and nondiapausing mosquitoes. This revealed low diversity but high variability between individual samples suggesting that no specific microbiota was associated with diapause in C. pipiens. By comparing physiological metrics of mosquitoes with low bacterial load (LBL) to conventional and reconstituted mosquitoes, we were able to determine that the microbiota, as a whole, impacts diapause preparation. LBL mosquitoes accumulated less mass and lipid reserves and experienced lower survivorship, likely due to an inability to process sugars to accumulate lipid reserves, a critical component of diapause preparation.To better understand biotic and abiotic factors that influence C. pipiens diapause we investigated how the whole-body microbiota changed over the course of diapause and in response to rearing location (field or lab). This revealed rearing location greatly impacted C. pipiens microbial composition, especially late in diapause, suggesting that future studies should incorporate field rearing to ascertain a more accurate depiction of mosquito-microbiome-dormancy associations. Finally, our investigation into how C. pipiens realized immune function changed in response to diapause status, age and temperature revealed that only temperature greatly impacts these processes. When challenged with Pseudomonas aeruginosa, mosquitoes held at 12? died at a significantly slower rate than those held at 18? or 6?. Wound closing was also impaired at 6? while normal melanization occurred at the other temperatures investigated. This suggests that although 6? is within the ideal temperature range to suppress metabolism and extend diapause duration based on previous studies, these diapausing mosquitoes are unlikely to survive at this temperature if wounded or infected. Overall, this dissertation provides a better understanding of C. pipiens diapause, revealing the importance of the microbiome in diapause preparation and providing a baseline for whole-body microbial composition during diapause in both lab and field settings. The survey of C. pipiens realized immune response during diapause in various conditions also greatly expands our understanding of this program. These studies reveal aspects of Culex diapause that should provide a solid foundation for future studies on which to expound upon in relation to mosquito-microbiome-dormancy interactions.