Summary

• 1.  Apparatus used in trapping flies and for collecting and examining their dejecta are described.
• 2.  Data relative to the dissemination of cysts and ova of human intestinal parasites by flies on Guam are presented.
• 3.  The transportation of viable cysts of Endamoeba histolytica by flies to a kitchen table in a native home has been demonstrated.
• 4.  A description is given of the transportation of ova of hookworm by flies (presumably from a poorly constructed latrine on the premises) to scraps of food on the ground where they hatch, yielding larvae that complete the free-living portion of the life cycle ending in the infective filariform stage.
• 5.  A note has been made of the more important species of flies encountered. The difficulties of fly control in the face of large scale breeding in latrines that are poorly constructed and maintained are cited.

The authors wish to acknowledge with thanks the assistance of members of the Entomology Laboratory: Lt. Commander G. E. Bohart, H(S), USNR, G. R. Norris, CPhM and J. F. Spitzer, PhM 2/c; also members of the Parasitology Laboratory: Lt. Commander N. R. Stoll, H(S), USNR, J. S. Gunter, PhM 3/c and K. O. Kramer, PhM 2/c. We are indebted to J. H. Thrasher, CPhM, for the photographs.