introduction Chiggers, vertebrate infesting larvae of the mite family Trombidiidae, have recently assumed much importance in medical entomology because of their demonstrated ability to transmit a fatal disease, river fever, to man and their probable relation to the transmission of pseudotyphus. Both of these diseases occur in eastern Asia, and they are very similar in their nature and symptoms.
In America our knowledge of the Trombidiidae is rather limited, particularly our knowledge of the larvae and the life histories of the different species. The most comprehensive paper which we have on them is by C. W. Howard (Howard, 1918) which deals with species occurring in Minnesota. Many years ago C. V. Riley studied the Trombidiidae, to a large extent incidentally, it appears. Yet he described as new two larvae which were reported as attacking man. More recently Chittenden (Chittenden, 1915) made various observations on chiggers and paid some attention to their control.