The direct change of bug larvae into adults is compared to the two-step metamorphosis of beetles, whose larvae change into adults via a stage called the pupa. The developmental transitions are regulated by changing activities of hormones and genes, depicted by the curves. The illustration accompanies an article by Konopova and colleagues in PLoS ONE (2011).
Konopova B, Smykal V, Jindra M (2011) Common and distinct roles of juvenile hormone signaling genes in metamorphosis of holometabolous and hemimetabolous insects PLoS ONE 6: e28728. DOI: 10.1371/journal.pone.0028728