440 
OBSERVATIONS ON THE HABITS AND PARASITES 
OF COMMON FLIES. 
By G. S. GRAHAM-SMITH, M.D., 
University Lecturer in Hygiene , Cambridge. 
(With Plates XXIII-XXX, 17 Text-figures and 9 Charts.) 
CONTENTS. 
PAGE 
Introduction . . . . . . . . .441 
The wintering habits of flies ...... 442 
The emergence of flies from pupae ..... 448 
The process of emergence from the puparium . . 449 
Conditions influencing emergence ..... 452 
The multiplication of flies ....... 455 
The causes of mortality amongst flies ..... 462 
Blow-flies emerging in the spring from winter pupae . 463 
Blow-flies belonging to the summer generations . . 463 
Blow-flies in winter ....... 465 
Flies entering houses ........ 466 
Species entering rooms....... 467 
House-flies in the kitchen . . . . . . 471 
Observations by means of traps on the factors influencing the 
outdoor habits of flies . . . . . . .473 
Purposes of the investigations ..... 473 
Open traps, constructed of mosquito net . . . 474 
Galvanised iron traps, or “tins” . . . . . 475 
Situations of the traps and baits employed . . . 476 
Common species of flies found out-of-doors . . . 477 
Seasonal distribution and abundance of species . . . 482 
Numbers of flies caught in traps ..... 485 
Species of flies caught in traps ..... 493 
Sexes of flies caught in traps ..... 493 
Ages of flies visiting the various baits .... 494 
Flies visiting fruit ....... 494 
Outdoor habits of M. domestica ..... 496 
The influence of weather on flies ..... 496 
Outdoor habits of flies ....... 500 
" (a) Blow-flies confined in an outdoor cage . . . 500 
(6) “Wild” flies.. . .502 
The larvae of common flies ...... 502 
Wasps .......... 504 
Empusa disease ......... 506 
Mites . . . . . . . . . .511 
Pseudo-scorpions ........ 514 
Parasites of fly larvae and pupae (braconids and chalcids) . 523 
Conclusions ......... 537 
References .......... 541 
Addendum ......... 543 
