External morphological variation in larval pattern elements in the Hyles euphorbiae complex is documented and described from independent samples of numerous populations across Europe and North Africa. Variability in the distribution of black cuticle and other colours was found to be much higher within populations than previously believed and it proved difficult to characterize any species, subspecies and even local population unequivocally using this feature alone. A representative sample of larvae from the Canary Islands, Madeira, North Africa, Iberia, Italy, Germany, Eastern Europe, Malta, Greece and Yemen, is illustrated, supplemented by observations from photographs of larvae from the Middle East and Western Asia. Taxonomy-independent definitions of larval morphotypes demonstrate significant overlap between species. We discuss the results in the context of Western Palaearctic biogeography, postulating several areas of hybridisation between the more northern Hyles euphorbiae and more southern H. tithymali that have led to the mosaic distribution patterns observed, and consider the potential of these moths for tracking the future eff ects of climate change in the Mediterranean Basin.