1. These species have small abdominal appendages, but robust legs well adapted for walking. 2. Female crabs generally carry their eggs attached to the abdominal appendages until they hatch. 3. However, apterygotes ( bristletails and silverfish ) and many immature aquatic insects have abdominal appendages. 4. In this stage, the pleopods ( swimmerets; abdominal appendages ) become functional, and the animal closely resembles the adult form. 5. These vesicles are derived from the coxal and trochanteral endites ( inner annulated lobes ) of the ancestral abdominal appendages. 6. The abdominal appendages of modern chelicerates are missing or heavily modified while those of horseshoe crabs ( Xiphosura ) form gills. 7. However, since crabs use the first two pairs of pleopods ( abdominal appendages ) for sperm transfer, this arrangement has changed. 8. The eggs can sometimes be seen attached to the hairs on the second abdominal appendage of the female crab alongside her own eggs. 9. One reason for this could be that the modification of the abdominal appendages into male copulation organs emerged later than the evolution of flight. 10. The caterpillar has two abdominal appendages which serve as triggers to initiate a backward motion by which it grasps prey insects using spiny pair of forelegs.