Required for the synthesis of chitin. [(1->4)-N-acetyl-beta-D-glucosaminyl](n) + UDP-N-acetyl-alpha-D-glucosamine = [(1->4)-N-acetyl-beta-D-glucosaminyl](n+1) + H(+) + UDP Expressed in eggs (PubMed:11589574, PubMed:15777697). Not expressed in hatched second-stage juveniles or in young females (PubMed:15777697). May require proteolytic cleavage for activation. RNAi-mediated knockdown causes a delay in egg hatching. Belongs to the chitin synthase family. Class IV subfamily.