Related Clues:

• Positive or intransigent
• Obstinate and unrepentant
• Completely determined
• Refusing to change one's mind
• 'Sullen, sour (4)'
• Morose, sour
• Can this, being so forbidding, be so frank?
• One might, to be sure, claim that this was the insect of 3 down
• Can one be so sure that this was the father of all insects?
• Can one be so positive that that's an insect mother?
• One may be positive that that was the very first insect
• One may be positive that this was the first of all the insects
• How a 18 down may may positively get to be six feet long
• One may be definite that this was the first of all the insects
• First man gets firm over the insect