The Biology of The Alder Flea-Beetle. 251 



found in Lewiston, nor in Hancock and Washington Counties. 

 Mr. John D. Tothill informed me that the beetles were present 

 and abundant in New Brunswick, and Dr. Robert Matheson, in 

 Nova Scotia. 



So far as Maine is concerned, the year of maximum abun- 

 dance was 1914. Even in the single township of Orono, the 

 individuals of this species must have numbered many millions. 

 The leaves were riddled by the attacks of the hibernating adults 

 even before the larvae appeared. By the middle of August 

 practically all of the leaves of every alder bush in the township 

 had been skeletonized by the larvae, and the trees looked brown 

 and bare, as though they had been swept by a fire. Many of the 

 leaves had dropped from the trees, forming a mat half an inch 

 or more thick under alder clumps. Some idea of the abundance 

 of these insects may be obtained from the following data, which 

 represent typical cases, illustrative of the condition of all of 

 the shrubs in an alder copse covering several acres : on a twig 

 selected at random, on which only the three last leaves were 

 left, were found 115 larvae, 31 on the terminal leaf, and 56 and 

 28 respectively on the other two ; on a single large leaf close 

 by were counted 77 larvae. By the first of September the trees 

 were practically leafless. The majority of them had put out 

 new leaves which were eaten by the beetles as fast as they were 

 produced. Such a serious infestation killed many of the trees 

 even in a single season. 



In the summer of 1915, there was a great reduction in the 

 number of the beetles, and although they were still common 

 locally, their range was so much restricted, that the writer knew 

 but few localities in the whole township where he could obtain 

 these insects. They were so rare in 1916 that even with diligent 

 searching the writer found no larvae and only a single adult in 

 Orono, and this condition seemed to be typical of that prevail- 

 ing all over the state. 



The writer can oft'er no satisfactory explanation of this 

 extraordinary disappearance. It certainly was not due to any 

 failure of the food supply through over-population, nor was it 

 due to the activities of natural enemies, for the parasitic forms 

 preying upon these insects were not sufficiently abundant to 

 cause a wholesale destruction, and they are but little troubled 

 by birds. Climatic conditions in the winter of 1914—15 were 



