INJURIOUS INSECTS OF 1904. 93 



important adjunct to agriculture. It is claimed that the annual loss 

 on crops in the United States from insects and fungi ranges from 

 $300,000,000 to $500,000,000, and that 75 per cent of this can be 

 saved by judicious spraying. Our state is not only taking a stand as 

 a fruit-raising state, but the conditions of raising vegetables, root 

 crops, etc., have become such that frequently spraying is an impera- 

 tive necessity. The Entomologist has been asked by agriculturists 

 and horticulturists to discuss this subject fully, since in many in- 

 stances money and time are wasted through ignorance of the essen- 

 tial principles of spraying, coupled with a lack of knowledge of the 

 habits of certain insects. Some insects eat the surface of twig, or 

 leaf, or bud, or fruit, and can be killed with internal poisons such as 

 Paris green, arsenate of lead, London purple, hellebore and the like. 

 But others, from the fact of their inserting a beak and sucking the 

 sap from below the surface, cannot be reached by any arsenical or 

 other poison applied to the surface, but must be sprayed or washed 

 with some oily or soapy mixture, such as soapsuds, whale oil soap, 

 kerosene emulsion, petroleum and the like, something which will 

 stop up the spiracles (little holes along the side of the body through 

 which they breathe), or will so irritate or burn the surface of their 

 bodies, sometimes also stopping the spiracles, as to cause death. 

 Such agents are found in tobacco water, pyrethrum, lime, sulphur, 

 lime-sulphur (and salt) solution, potash, lye, etc. 



We can therefore readily divide Minnesota insects into two well 

 marked groups, those which are mandibulate or biting, and those 

 which are haustorial or sucking. Under the first class we have cut 

 worms, army worms, potato beetle or "potato bug," codling moth 

 or "apple worm," currant worms, wire worms, borers, plum curculio, 

 tent caterpillars, canker worms, pear and cherry slugs, cucumber 

 beetle, sometimes wrongly called "squash bug," and many others ; 

 in short, all insects which have biting mouth parts when they attack 

 our crops. Under the second class — sucking insects — we have chinch 

 bugs, all plant lice, leaf hoppers, true squash bugs and scale insects. 



Do not therefore use Paris green or any internal poison against 

 plant lice or bed bugs, both of which mistakes on the part of our 

 citizens have come to my notice. 



