146 MASS. EXPERIMENT STATION BULLETIN 177. 



Among the predatory enemies of plant lice, lady beetles and their 

 young, and the larvae of syrphus flies, are most important. Both as 

 adults and during the immature stages, lady beetles are voracious feeders 

 upon plant lice as well as upon other tiny insects. The average person 

 readily recognizes a lady beetle and knows its beneficial habits, but the 

 lady beetle young, being of an entirely different appearance, are often 

 mistaken for injurious forms and unfortunately are destroyed. These 

 young vary in length all the way up to about a half inch, are bluish or 

 blackish in color, often with orange spots on the back, and resemble very 

 much a miniature alligator in general appearance. They crawl about 

 freely, destroying large numbers of the plant lice. The syrphus fly young 

 are maggot-like forms, being pointed at the head end and somewhat 

 broader behind, and are of variable length but average about one-fourth 

 of an inch. These are ordinarily orange, greenish or whitish in color, are 

 very sluggish, but destroy, nevertheless, numbers of the plant lice. 



Tiny, almost microscopic, wasp-like insects also aid in the destruction 

 of plant lice, their young living parasitically in the bodies of these pests. 



During certain seasons, especially when there is an abundance of warmth 

 and moisture, a fungous parasite attacks these plant lice and destroys 

 large numbers. In some localities this disease has been credited with 

 having practically exterminated the plant lice after they had become 

 numerous enough to menace seriously the potato crop. 



Acknowledgments. 



The foregoing is not presented as a "distinct contribution to scientific 

 knowledge," but is merely an attempt to present in available form facts 

 already determined by others, together with results of personal observa- 

 tions and experience. 



The writer wishes to acknowledge credit to Bulletin No. 147, Maine 

 Agricultural Experiment Station, for certain facts and suggestions made 

 use of in this paper; and is indebted to Mr. A. I. Bourne of the Massa- 

 chusetts Agricultural Experiment Station staff for assistance in carrying 

 out the insecticide tests. 



The work has been carried out under the direct supervision of Dr. H. T. 

 Fernald, whose kind co-operation has been of much help. 



