With the abundant material he had at his disposal, he worked mainly on mites and also did some work on the spiders of Australia, the islands of the Indian Ocean, India and Africa.
With the abundant material he had at his disposal, he initially described new spiders, harvestmen, scorpions and millipedes, but soon worked mainly on mites and ticks. He also did some work on the spiders of Australia, the islands of the Indian Ocean, India and Africa.