120 



IiJ.iNois Naturai. History Survey Bulletin 



Vol. 27, Art. 2 



system is but half uiitierstood, that we heed- 

 lessly complain of its imperfections. We blame 

 the house-flies for annoying us, and fail to see 

 that in the larva state they have cleared away 

 impurities around our dwellings, which might 

 otherwise have bred cholera and tvphus fever. 

 We execrate the blood-thirstv mosquito, and 

 forget that in the larva state she has purified 

 the water, which would otherwise, by its ma- 

 larial effluvia, have generated agues and 

 fevers. In all probability, when we rail at the 

 Tahanus that torment our horses in the summer, 

 we are railing at insects which, in the larva 

 state, have added millions of dollars to the 

 national wealth, by preying upon those most 

 [insidious] and unmanageable of all the insect- 

 foes of the farmer — subterraneous, root-feeding 

 larvae (Walsh quoted in Cresson et al. 1865: 

 18). 



An editor of The Practical Entornolo- 

 gist, in commenting on Walsh's paper, 

 cautioned his readers: 



Before you undertake to kill off the larvae 

 of the Horse-flies and the Mosquitoes, you had 

 best make yourself quite sure that they are 

 really your enemies, and not, as Mr. Walsh 

 maintains, some of vour very best friends 

 (Cresson ct al. 1865:18). 



Flies and mosquitoes passed practically 

 unmentioned until about 1880 when, be- 

 cause of the insects' annoyance and nui- 

 sance characteristics, a few workers began 

 to investigate suppressive measures. Win- 

 dow screens and the use of smoke came 

 into the picture first, followed by oil 

 sprays, crude repellents, and several fly 

 traps. If we exclude the modern insecti- 

 cides developed since 1940, most of the 

 control measures that are recommended 

 today for the control of flies and mos- 

 quitoes had been developed by 1900. By 

 the combined use of drainage, good sani- 

 tation practices, screening, and the known 

 insecticides such as lime, borax, oils, ar- 

 senicals, and pyrethrins, public health 

 agencies made remarkable progress in re- 

 ducing the incidence of insect-borne dis- 

 eases, but it was not until DDT and the 

 more recent synthetic organic insecticides 

 became available that it was possible to 

 reduce fly and mosquito numbers to the 

 near vanishing point and to eradicate al- 

 most all insect-borne diseases of man. 



Shortly before the outbreak of World 

 War I, the country embarked on an all- 

 out "Swat-the-Fly" campaign that car- 

 ried over into the dairy industry. This 

 campaign stimulated interest in the devel- 

 opment of sprays for use on livestock, as 



well as space spra\s for use in and around 

 buildings. 



Unfortunately, many of the formula- 

 tions used prior to the late 1930's were 

 only partially effective in controlling 

 flies, and in many cases the injury they 

 inflicted on cows exceeded the benefits de- 

 rived. It was difificult, if not impossible, 

 to establish clearly the fact that flies did 

 affect milk production and that good fly 

 control would pay dividends in the form 

 of higher milk production. In the last 

 10 years, with the new insecticides such 

 as DDT, methoxychlor, and several ef- 

 fective organo-phosphates, and with some 

 repellents far more effective and much 

 more persistent than anything available 

 prior to 1*^40, it has been possible to dem- 

 onstrate that good control of flies, 

 whether they be tabanids, stable flies, or 

 horn flies, will result in an increase of 

 milk production of as much as 10 to 25 

 per cent. The exact gains depend upon 

 the intensity of the fly population, the 

 species involved, and the duration of the 

 attack. Significant findings in this field 

 have been reported in a number of scien- 

 tific articles (Bruce & Decker 1951, 1957, 

 1958; Bruce 1952, 1953). 



BIOLOGICAL CONTROL 



Man discovered at a very early date 

 that not all insects are bad, that some are 

 definitely his allies, some are indifferent 

 or neutral, and some are in the category 

 of Dr. Jekyll-Mr. Hyde — half good and 

 half bad. Walsh, Le Baron, Thomas, and 

 other early entomologists in their writ- 

 ings repeatedly referred to the necessity 

 of distinguishing between man's foes and 

 friends in the insect world, and empha- 

 sized, as did their successors, the import- 

 ance and potentialities of parasites and 

 predators in the natural control of insects. 



In December, 1854, William Le Baron, 

 who 16 years later became the second 

 State Entomologist of Illinois, wrote: 



Birds benefit the agriculturist by destroying 

 countless mvriads of noxious insects, whilst 

 thcv injure him by consuming a part of those 

 products which he would fain reserve for his 

 own exclusive benefit. But it is the universal 

 testimonv of those who have investigated the 

 matter, that the evil compared with the good 

 which thev accomplish is extremely trivial. 

 Probably every reader of ornithology will call 



