14 



FIELD WORK AGAINST GIPSY AND BROWN-TAIL MOTHS. 



amount of food available. It is a noticeable fact that in bad colonies, 

 where most of the foliage has been eaten, the caterpillars pupate early 

 in the season before attaining normal size. 



This insect has a varied list of food plants; in fact, it will eat 

 almost any kind of vegetation, although it seems to prefer the foliage 

 of oaks (fig. 1), willows, and apple trees. Repeated observations 

 have shown that the ash {-R-g. 1), juniper, and red cedar are practically 

 immune from attack, while the maple is not injured to any great ex- 

 tent if more desirable food is within easy reach. Grass and garden 

 crops are sometimes seriously injured when the supply of other food 

 has been exhausted. 



A few years ago a farmer in Lynn, Mass., stated that with the assist- 

 ance of his men he collected several bushels of the caterpillars that were 



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Fig. 1.— Roadside view in Massachusetts, showing oak and ash trees, the former killed by the gipsy moth 

 {Porthetria dispar) and the latter practically uninjured, (Original.) 



feeding in his field of sweet corn. The caterpillars had stripped the 

 trees in a piece of woodland near by, and, after eating all the foliage 

 from the bushes and low growth, had migrated in countless numbers 

 across the road and attacked the growing corn. 



Most of our native leaf-eating insects confine their diet to a small 

 number of food plants, and it is unusual for a species to feed on both 

 deciduous and coniferous trees. The gipsy-moth larvae, after becom- 

 ing half grown, feed with avidity on conifers, especially the white pine, 

 and many acres of this, as well as other coniferous trees, have been de- 

 foliated and killed in the infested region of New England (fig. 2). 



