Dear Reena, I would suggest to use the CTAB method. Have a look at the publication I attached. I used the modified protocol by Reineke for insects (downstream applications: PCR and AFLPs).
Hey Reena, I work on polychaete worms as well...and so you can use the phenol chloroform protocol as well. I myself have not tried it yet (i will be soon) but other people have used it on other invertebrates and they have gotten excellent DNA yields.