Figure 1.

The ‘TI–J–LiFe’ network. The TI–J–LiFe network represents a set of interacting pathways that comprise the nutrient sensing TOR (target of rapamycin) and IIS (insulin/insulin-like growth factor 1 signalling) pathways, the Juvenile Hormone (JH, a major lipophilic hormone whose production is regulated by IIS and TOR), as well as downstream processes targeted by this network, including somatic maintenance functions (e.g. immunity and oxidative stress resistance) and reproductive physiology (including vitellogenins and yolk proteins), that have profound effects upon insect life history, especially on Lifespan and Fecundity. This network is thought to be one of the major regulatory circuits underpinning variation of insect lifespan and the trade-off between fecundity and longevity. The core components and feedback loops depicted here are mainly based on experimental findings in Drosophila melanogaster (for detailed information, see https://flybase.org; e.g. IIS gene lists at: https://flybase.org/reports/FBgg0000904.html; https://flybase.org/reports/FBgg0000900.html; https://flybase.org/reports/FBgg0000898.html). Previous work suggests that this network and its effects are evolutionarily highly conserved among insects beyond Drosophila. In some social insects (e.g. Apis mellifera), some parts of this network might be ‘wired’ differently, but whether such a ‘rewiring’ is common among social insects remains largely unknown (for further discussion, see [18]). (Online version in colour.)