108 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



collection as Hylotoma pectoralis Leach, and its larvae (pi. vm, 

 fig. 5) also agree with specimens preserved in the National 

 collection. There may be, however, some doubt as to the cor- 

 rect determination, since the only records we have on the food 

 habits of the saw-flies are not in accord with those recorded 

 here. Rev. Thomas W. Fyles, in the Canadian Entomologist 

 (1886, vol. 18, p. 38), has noticed these larvae in great numbers 

 feeding on the white birch in the vicinity of Quebec during the 

 month of September, Mr. John George Jack (Psyche, vol. 

 6, 1891, p. 10) bred the saw-fly from larvae found the previous 

 summer feeding on the foliage of Bctula alba in the Arnold 

 Arboretum at Jamaica Plain, Mass, and Dr. Dyar (Can. Ent., 

 vol. 27, p. 210, 1895) found them on Betula lenta at Wood's 

 Hole, Mass., and on Betula papyrifera at Keene Valley, N. Y. 

 Near Washington, D. C., is a species feeding exclusively on 

 the black willow (Salix nigra}, leaving intact every other species 

 of willow and never being found on the only species of birch 

 (Betula nigra) that occurs on the banks of the Potomac. The 

 full extent of the injury is not known to us. Mr. H. S. Bar- 

 ber traced the injury along the banks of the river from near 

 Washington up to Seneca, a distance of about 22 miles. All 

 the willows growing on the more elevated ground were left 

 intact. 



The accompanying series of photographs were made by 

 H. S. Barber. 



EXPLANATION OF PLATES. 



PLATE VII. 



Hylotoimi pectoralis: Willows defoliated by the larvae. 



PLATE VIII. 



Hylotoma pectoralis : 



1. Female ovipositing. 



2. Eggs just laid. 



3. Eggs nearly ready to hatch. 



4. Imagos, male and female. 



5. Full-grown larvae. 



6. Cocoons. 



7. Dormant larvae from cocoons. 



PLATE IX. 

 Hylotoma pectoralis: 



8. Larvae destroyed by fungus. 



9. Cocoons upon the ground. 



10. Pupae, male and female, dorsal and ventral views. 



