MISCELLANEOUS PAPERS. 291 



Parasitic and Preclaceoiis Insects. 



la a paper by Prof. Riley, recently read before a California Farmers' 

 iDstitute, that distinguished authority expressed the opinion that the 

 importance to agriculture of the parasitic and predaceous insect ene- 

 mies of such species as injure vegetation had been somewhat over- 

 estimated by the earlier writers, because while in the abstract they are 

 essential to keep the plant-feeding species in check, and without them 

 these latter would be much more difficult to manage, yet in the long 

 run our worst insect enemies are not materially affected by them, and 

 the cases where the multiplication of the beneficial species can be arti- 

 ficially encouraged are relatively few. There are but two methods by 

 which the insect friends can be utilized, because they are usually 

 beyond the farmer's control. One is the intelligent protection of those 

 species that are indigenous, and the other the introduction of desirable 

 species that do not already exist here. The first method offers com- 

 paratively few opportunities for its exercise, although there are some, 

 and the instance given by Dr. Fitch is quoted in which a man com- 

 plained that his rose bushes were more seriously affected by aphides 

 than those of his neighbors, notwithstanding the fact that he had been 

 careful to destroy all the old parent bugs, he having mistaken the 

 beneficial lady-birds, which feed on the arphides, for the parent of the 

 pest. So in a case quoted by Mr. Howard, the army worm was taking 

 a field of timothy and threatening to overrun adjoining fields when the 

 owner observed the appearance of large swarms of the red-tailed 

 tachina fly, the enemy of the worm. He assumed that the fly was the 

 parent of the worm and gave up the contest in despair, letting all the 

 fields go, when, in fact, with the aid of the natural allies he might have 

 saved them. Here lack of knowledge caused the loss. 



For many years well-informed gardeners in Europe have been in 

 the habit of collecting lady-birds and some forms of ground beetles to 

 turn loose on plots infested with plant-lice or cut-worms, and Prof. 

 Eiley thinks that the characteristics of these two families should be 

 taught in the public schools, so that use may be made of the knowledge 

 by the cultivator. So, in the instance of case insects, which hibernate 

 in cases attached to twigs of trees, such as the Eascal leaf-crumpler 

 and bag worm, the proper course is to. collect the cases and not burn 

 them, but instead, to transport them to the center of a large, treeless 

 field, when such of the worms as emerge will wander about for a few 

 jards and then die for want of favorable conditions, while the para- 



