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MicroRNAs are ubiquitous in the genomes of metazoans. Since their discovery during the late 20th century, our understanding of these small, noncoding RNAs has grown rapidly. However, there are still many unknowns about the functional significance of miRNAs — especially in non-model insects. Here I discuss the accumulating evidence that microRNAs are part of gene regulatory networks that determine not only the developmental outcome but also mediate transitions between stages and alternative developmental pathways. During the last 20 years, researchers have published a multitude of profiling studies that describe changes in miRNAs that may be important for development and catalog potential targets. Proof-of-principle studies document phenotypic changes that occur when candidate genes and/or miRNAs are inhibited or overexpressed. Studies that use both of these approaches, along with methods for confirming miRNA–mRNA interaction, demonstrate the necessary roles for miRNAs within gene networks. Together, all of these types of studies provide essential clues for understanding the function of miRNAs in the developmental toolbox. 

The maternal regulation of diapause is one type of phenotypic plasticity where the experience of the mother leads to changes in the phenotype of her offspring that impact how well-suited they will be to their future environment. Sarcophaga bullata females with a diapause history produce offspring that cannot enter diapause even if they are reared in a diapause inducing environment. Accumulating evidence suggests that microRNAs regulate diapause and, possibly, maternal regulation of diapause. We found significant differences in the abundances of several microRNAs (miR-125–5p, miR-124–3p, miR-31–5p, and miR-277–3p) in brains dissected from adult female S. bullata that had experienced diapause compared to females with no diapause history. We also found moderate differences in the mRNA expression of the circadian-clock related genes, clock, clockwork orange, and period. MiR-124–3p and miR-31–5p are part of a gene network that includes these circadian clock-related genes. Taken together our results suggest the maternal block of diapause in S. bullata is regulated, at least in part, by a network that includes microRNAs and the circadian clock. 

Winter provides many challenges for insects, including direct injury to tissues and energy drain due to low food availability. As a result, the geographic distribution of many species is tightly coupled to their ability to survive winter. In this review, we summarize molecular processes associated with winter survival, with a particular focus on coping with cold injury and energetic challenges. Anticipatory processes such as cold acclimation and diapause cause wholesale transcriptional reorganization that increases cold resistance and promotes cryoprotectant production and energy storage. Molecular responses to low temperature are also dynamic and include signaling events during and after a cold stressor to prevent and repair cold injury. In addition, we highlight mechanisms that are subject to selection as insects evolve to variable winter conditions. Based on current knowledge, despite common threads, molecular mechanisms of winter survival vary considerably across species, and taxonomic biases must be addressed to fully appreciate the mechanistic basis of winter survival across the insect phylogeny. 

Dormancy is evolutionarily widespread and can take many forms, including diapause, dauer formation, estiva- tion, and hibernation. Each type of dormancy is characterized by distinct features; but accumulating evidence suggests that each is regulated by some common processes, often referred to as a common “toolkit” of regulatory mechanisms, that likely include noncoding RNAs that regulate gene expression. Non- coding RNAs, especially microRNAs, are well-known regula- tors of biological processes associated with numerous dormancy- related processes, including cell cycle progression, cell growth and proliferation, developmental timing, metabolism, and en- vironmental stress tolerance. This review provides a summary of our current understanding of noncoding RNAs and their in- volvement in regulating dormancy.