 Using what was probably the world's most complete collection of fleas of about 260,000 specimens (representing some 73% of the 2,587 species and subspecies so far described), he described around 500 species and subspecies of Siphonaptera.He was followed in this interest by his daughter Miriam Rothschild, who helped to catalogue his enormous collection of the insects in seven volumes.Fleas have a significant economic impact.