Swastikas and cockchafers

I'm idly looking through Angela Brazil's books on Project Gutenberg and goodness, her schoolgirls are an exhausting, alarming, sometimes incomprehensible lot:

"Dona, you're ostriching! For goodness' sake brace up, child, and turn off the water-works! I thought you'd more pluck. If you're going to arrive at Brackenfield with a red nose and your eyes all bunged up, I'll disown you, or lose you on the way. Crystal clear, I will! I'll not let you start in a new school nicknamed 'Niobe', so there! Have a caramel?"

- A Patriotic Schoolgirl

"You've got to reckon with me if you spoil the play, so there! Don't be a silly cockchafer!"

- The Princess of the School

"O Sophonisba!" ejaculated Raymonde.

- The Madcap of the School

"I drew a tiny little swastika inside the envelope, and I made three crosses over it with my right forefinger," confessed Hilary.

- A Harum-Scarum Schoolgirl

Annie really played up magnificently. None of the girls had known before that she could act so well. She threw such fervour into her love-making that Mrs. Morrison, who was among the spectators, gave a warning cough.

- A Patriotic Schoolgirl

"I didn't mind a bit after my 'first mad' cooled off. Sorry if I was a bear. No, I won't take your lucky hunchback. Must I? Well, you're a dear! I'd adore to have it. I felt absolutely green when I saw you buy it. I'll hang him on a chain and wear him round my neck, and I expect I'll just be a whiz at tennis to-morrow. Oh, isn't he funny? Thanks ever so! I shall keep him eternally as a memory of this ripping day up old Vesuvius."

- The Jolliest School of All

I'd love to know the origins of 'cockchafer' (and what it's meant to mean, other than the obvious) but I'm reluctant to go a-googling since I'm guessing that most of the results won't be innocent pre-WWI schoolgirl larks.