The highlight in entomorph eyes is so's the audience can read their expressions easier, yep. I could try to fake up some explanation about how they focus the compound lenses so the light hits them a certain way, but it's really cartoon shorthand.
...I think this is the first time I just CAN'T decide which panel I like best - they are all great! From 'ah! giant bug!' and 'ah, he's touching me! D: ' through 'everyone crowds protectively around Tal' to Tal's angry 'touch my favorite space peoples and be horribly imprisoned' face.