The reading for this one is a weird one. It uses the kun'yomi readings for both, meaning you'll have to pull your knowledge of the word 弱い from earlier and apply it here. 虫 should be okay, though, as this is the reading you learned with the kanji.
Just remember, only weak bugs use kun'yomi, and that weak bug is you in this instance.
My son, who was such a weakling and a crybaby, is already an adult.
Many Americans are cowards who can't even eat a bit of natto.
Cowards should be treated like hairy caterpillars - picked up and thrown out!