Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
Washington, D. C. Vv December 3, 1921 
STUDIES ON THE BIOLOGY AND CONTROL OF 
CHIGGERS. 
By H. E. Ewine, Specialist in Mites. 
CONTENTS. 
Page. Page 
PUNO GUCELOTIANe Ate eae Eee ee 1-| Injury—Continued. 
Speclesm concernede eae aa ee 1 VOC ere RA Tb aly fib care esa ve gh ee Se nae 10 
Notes on seasonal history_________ 2 General disturbances__________ 11 
POCA EGIStriDUbioN Ale Yi tes Se Tae 3 Relation to disease___________ 12 
Habits of unattached larve________ SPs COMET Ole e eee 2 ae te I a cis eee 13 
ENG SUS ee esa Dieu ener 5 Protection against chigger at- 
LUTE TOTS Ah SN 8 pa eI a aN q COREY eect pM i gus alt ay ee 18% 
Chigger injury confused with Destruction of breeding places_ 15 
many other kinds of injury__ 7 Destruction of the  chiggers 
Do chiggers penetrate the skin? 8 themselves Sk Si aes ee) 17 
Do chiggers enter the pores of ATTA CLV CS ae eee ra kG acs 18 
EL OWE SU eva a ie are ES a coe Oabitenatwnrem cite dss: ae ae ee 19 
Difference in susceptibility_____ 10 
INTRODUCTION. 
Notwithstanding the obvious economic importance of chiggers, 
and an almost universal acquaintance with their injury, little has 
been done in the past to ascertain their habits in nature or to find 
efficient methods for their control. Because of these facts the writer 
decided early in the season of 1919, with the approval of Dr. L. O. 
Howard, Chief of the Bureau of Entomology, to begin a series of 
experiments and observations on their biology and control. The 
work was started in June of that year and continued until the fall of 
1920. For various reasons it was thought advisable to discontinue 
the work then for some time, hence the results thus far obtained have 
been prepared for publication. It is the expectation of the writer, 
in the near future, not only to complete the life history for at least 
one of our species, but to give a synopsis of the taxonomy and dis- 
. tribution of the species occurring in the United States. 
SPECIES CONCERNED. 
Years ago C. V. Riley (10)? described from this country (“south- 
western States”) two chigger species under the familiar names of 
* Reference is made by number (italic) in parentheses to “ literature cited,” page 19. 
55672°—21 1 
