190 



STATE BOARD OF AGRICULTURE 



Potato-beetle parasite (Phorocera iloryphorae), original. 



and a small grub bores into its host, feedinfj on the living flesh and the juices of the 

 body, but avoiding the vital paits. After the maggot has become full grown in its 

 living host, and after the larva of the beetle has descended into the ground to pupate, 

 the maggot changes to a puparium, corresponding to the cocoon stage of some in- 

 sects. From this puparium issues another fly similar to the one which originally laid 

 the egg. This goes on a number of times in a season, each generation of the flies de- 

 stroying a number of potato-bug larva;. 



Specimens of the potato-bug larvse, with eggs of the fly on them, were sent the 

 writer by Mr. Geisniar, and were placed in suitable cages in order to watch the 

 transformations. The larva; went into the ground just as they should, but only one 

 fly has, as yet, come forth. It is possible that more will emerge next spring. The 

 process of depositing the egg is described in a letter by Mr. Geismar, who says: ''I 

 noticed a fly walking around a beetle in a peculiar way, touching it from time to 

 time. As soon as the beetle appeared dormant the fly commenced to lay its eggs on top 

 of the beetle, always keeping its head toward it and circling around it once or twice. 

 The fly, to lay its egg in that position, passes the appendage under its body and head 

 and raising it somewhat above its head drops an egg on tlie top of the beetle." 



A number of adult beetles, each bearing from one to sixteen eggs, were placed in a cage 

 with food, in hopes that the larvae miglit work on them. These beetles lived from 

 July 12 until August 21, at which time the writer went away and no more observations 

 were taken. No signs of attack, however, by the parasites were to be seen. Most of 

 the eggs dropped off one at a time. 



An attempt was made to introduce the flies here, in order to get them to work on 

 our potato-beetles, but as no fresh flies emerged, it was impossible. A little later in the 

 season four flies, which the writer is unable to distinguish from tlie potato-beetle 

 parasite, were bred from cut-worms. The cut-worms were the last two of a large 

 number of rapidly disappearing depredators in a field of oats and peas. They cut the 

 oat stems into sections several inches long and also cut the pea vines. The larvae 



