 The gonopods may fuse with the epandrium in genera such as "Hydrophorus", "Thrypticus" and "Argyra", or there may be a suture, as in the genera "Porphyrops", "Xiphandrium" and "Rhaphium".In some genera, such as "Hypophyllus" and "Tachytrechus", the surstyli are well-developed as secondary outgrowths of the epandrium.In genera such as "Tachytrechus", there are two pairs of surstyli—one proximal and one distal.