PART I. 



EEPORT OF D. W. COQUILLETT. 



Prof. Cyrus Thomas, State Entomologist of Illinois : 



Dear Sir — The following pages constitute my report on the Inju- 

 rious Insects of Northern Illinois : 



During the year 1881 several insects which had not heretofore 

 been known to occur in destructive numbers in this part of the 

 State, appeared in several localities in considerable numbers, some- 

 times committing extensive ravages. 



Prominent among these is the Corn Worm or Boll Worm {Helio- 

 this armigera, Hubner,) which I have occasionally met with in past 

 years, but not in numbers sufficient to occasion much damage. 



The present season, however, they appeared in destructive num- 

 bers in a great many fields of corn, doing considerable damage, not 

 so much by what they devoured as by what they spoiled, as the ears 

 of com which they infested were nearly always more or less covered 

 with mould. 



Another insect which, so far as I am aware, has not heretofore 

 occurred in this section in destructive numbers, is the Imported 

 Currant Worm, {Nematus ventricosus, Klug,) which, the present sea- 

 son, completely defoliated the currant bushes in many gardens in 

 this locality. It is a very singular fact, and one almost without an 

 exception, that the insects which have been imported into this country 

 from Eui'ope are always more destructive than our native insects 

 which have the same habits. The difference in the climate of the two 

 countries may have much to do with this, but it is no doubt largely 

 due to the fact that the parasites which preyed upon them in their 

 native country were not imported with them ; for it is a pretty well 

 established fact that nearly every leaf-eating insect has a parasite 

 which mfests it, but which will not infest any other species, and for 

 this reason our native parasitic insects will not be likely to infest 

 an exotic insect that has been imported into this country. 



