March Bluetail Dameselfly – Ischnura senegalensis – Cape Town, South Africa
Parasites don’t tend to kill their hosts but want to keep it alive so they can stay longer. Many odonates suffer from parasites. Most remarkable are the mite larvae that can be seen on quite many odonates: small red or orange balls that are attached to their wing veins, thorax or abdomen.
Water mites undergo three active stages: larva, nymph and adult. In the larval stage they are parasites. In the other stages, they are predacious. Mite larvae start looking for a host as soon as they are born. When they find one (an almost full-grown odonate larva), they hide under it’s wing rudiment until the odonate larva emerges. Until then, they aren’t real parasites yet but only sit there, wait and travel along with the larva. That’s called forensic parasitism.
When the odonate larva emerges, the mite larva moves to the dragonfly or damselfly and attaches itself to it. On dragonflies, Arrenurus papillator larvae attach to the wing veins, on damselflies to the thorax or abdomen. Other mite species prefer other places.
On some dragonflies, hundreds of larvae were found. Such high infestation rates make the host animal weak, slow and light-weighted. The host dies when there are so many mite larvae on it’s body that the skin bursts!
After growing to many times it’s original size, the larvae wait until the host flies above water. The larva jumps down and changes into an aquatic, predacious nymph.
Cape Town – South Africa