Figure 1From: The ultrastructure of book lung development in the bark scorpion Centruroides gracilis (Scorpiones: Buthidae)Ventral view of embryo opisthosoma with spiracles (Sp) and small flap-like sternites (St) starting to form. Centruroides gracilis, supine. SEM. The spiracles evident here are near the posterior margin of segments 4, 5 and 6. The spiracles on segment 4 are only partially visible because the pectines (Pe) from segment 3 still overlap on the ventral surface of segment 4. The spiracles are open with no closing mechanism until after the first molt (second instar). Scale, 200 μm.Back to article page