February 2025

5 Buckden Roundabout February 2025 Fleas! Fleas Probably one of the most reviled insects, the flea has been plying its trade since the Jurassic period, over 150 million years ago. These ancient relatives lacked the jumping abili- ties of their modern cous- ins and were considerably larger (up to 21mm long) but still fed on blood. From the large, armoured mouth parts on the few fossils found it thought that their hosts were as equally as large, the dinosaurs. It was not until around 65 million years ago that the flea as we know it today emerged. There are currently thought to be around 2,500 species of the flea worldwide with some 60 species found in the UK. Much smaller than their ancient relatives they range in size from 1.5 to 3mm and are incredibly resilient ani- mals. Their body is amazingly tough, as anyone who ’ s tried to crush one with their fingertips can attest. The large back ‘ jumping ’ legs are only used as a method of escape as the flea has little control over the direction of travel, but the jump itself is impressive. Covering approximately 120 times their body length, it would be the equivalent of a human jumping some 200m into the air from a standing start, roughly 80 times the current world high jump record. However this method of locomotion uses enormous amounts of energy, so much in fact that if a flea were to jump continuously for 90 seconds it would boil its own body fluids. Overall, the total flea population at any giv- en time will only consist of 5% adult animals. The rest are made up of 50% eggs, 35% larvae and 10% pupae. This is possible because of the prodigious rate of repro- duction, with females producing around 5000 eggs in their lifespan of approx. 10 weeks. Flea species tend to be categorised by their preferred host and most are spe- cially adapted to that host. The Rab- bit Flea, for exam- ple, can detect cor- tisol and corti- costerone levels in the rabbit ’ s blood indicating that birth is imminent. The fleas move down to the back of the rabbit and once the babies are born, they move across, mate and lay their eggs on the young before returning to the parent animal. Flea bites cause little harm to the hosts beyond a small itchy red spot, it is the micro - organisms within the flea that cause the trouble. The most famous is, of course, the Black Death. Believed to have been spread by the Rat Flea, this pan- demic is thought to have wiped out almost half the popu- lation of Europe over less than 10 years in the mid - 14 th century. This is unlikely to be repeated in modern times, not least because the Black Rat, the Rat Flea ’ s host is now virtually extinct in the UK, and its cousin the ever - present Brown Rat do not harbour this flea. The disappearance of another flea species is not due to the loss of its host; increased hygiene standards mean the Human Flea is now very rare in the UK. Most bites on humans now are down to Dog and Cat Fleas jumping across from the family pet. Gregory Belcher Cat Flea Dog Flea Human Flea Oriental rat flea