KELATION OF BIRDS TO DISPERSION. 13 
ing injury, it would undoubtedly offer a valid explanation of the 
cause for some of the outlying colonies which have been found. In 
the report of Forbush and Fernald, already cited, detailed accounts 
are given of the part played by practically all the insectivorous 
birds which are at all common in eastern Massachusetts. At the 
time the observations were made a large number of trained field 
observers were constantly employed, and few, if any, of these re- 
ported that birds were found feeding upon eggs of the gipsy moth. 
In fact, the report states that the only bird that has been found 
feeding upon these eggs in the field is the English sparrow, and, as it 
is normally a grain-feeding species and one that frequents cities or 
centers of population, it is doubtful whether the moth would be dis- 
persed to any great extent if it were possible for the eggs to pass 
through the bird without injury. 
Fortunately, during the winter of 1909-10 two sets of experi- 
ments were conducted for the purpose of determining whether gipsy- 
moth eggs would pass through the alimentary canal of birds without 
injury. These tests were made independently, and in both cases 
it was necessary to disguise the eggs in other food or force the birds 
to feed upon them. One set of experiments was begun in February, 
1910, by Mr. C. W. Collins, 1 of the parasite laboratory of the Bureau 
of Entomology. He used a number of English sparrows and a single 
pigeon. 
The sparrows were fed by placing gipsy-moth eggs in their mouths 
and requiring them to take a swallow of water to wash them down. 
Of 356 eggs fed in this way 1-12 were found intact in the excrement 
and the balance were broken during the process of digestion or re- 
mained in the gizzard. Only seven eggs hatched, which shows that 
under this artificial treatment the chances for survival of the eggs are 
very small. None of the eggs fed to the pigeon hatched after being 
voided. 
These experiments indicate the extreme improbability of either 
of these birds selecting gipsy-moth eggs for food, and the chances 
of the insect being disseminated in this way appear very slight, both 
on account of the injury to the eggs in passing through the bird and 
because the distances of migration of the species are relatively small. 
The other set of experiments was conducted by Mr. Wm. Kieff, 2 
of the Bussey Institution, Harvard University, during March of the 
same year. As no native birds were available for the tests the follow- 
ing species were used : German canary bird, English yellow-hammer, 
English chaffinch, Japanese robin, screech owl, and carrier pigeon. 
The eggs were disguised in food, such as bread crumbs. In the case 
1 Some Results from Feeding Eggs of Porthetria dispar to Birds. Journal of Economic 
Entomology, vol. 3, no. 4, Aug., 1910, p. 343. 
2 Some Experiments on the Resistance of Gypsy Moth Eggs to the Digestive Fluids of 
Birds. Psyche, vol. 17, No. 4, Aug. 1910, p. 161. 
