NESTING OF SOME GUIANA BIRDS. 5 
Tyrannidz in the construétion of their nests. The 
nests of the Tyrant Shrikes are usually flat open struc- 
tures, but the Kiskadee builds a large globular, and the 
Pipiturie a long purse-like nest in which to lay its two 
small white eggs. The former bird is the commonest of 
its family found in the colony. It lays three eggs spotted 
with blackish brown, the spots being concentrated towards 
the larger end. Young Kiskadees are often infested 
with the /arvz of a species of Aéstrus, Dermatobia 
noxtalis, known here as the “Mosquito Worm.” At 
times these parasites are present in such astonishing 
numbers that it is difficult to understand how the birds 
can live to arrive at maturity. We have seen a young 
Kiskadee so infested with these disgusting larvze that 
it was unable to close its wings, while its body was 
distorted to such an extent as to be hardly recog- 
nizable. 
The Mosquito Worm also attacks the young of the red 
and yellow-backed mocking birds (Cassicus affinis and 
C. persicus.) Mr. BARSHALL informs me that these 
birds are frequently made the viétims of another member 
of their family, Cassidix Oryztvora, which deposits its 
eggs in their nests, and imposes upon them the ‘ask of 
rearing its young. I have myself taken the eggs of this 
bird from the nests of the larze black “ Bunyah,” Oséz- 
nops decumanus, but never could ascertain anything 
further concerning their history. 
Most of our Cassigues resort to trees already occupied 
by colonies of wasps for the purpose of building their 
nests. I suppose this is for protective purposes, but then, | 
why have not all of our bird; developed the same habit ? 
A marauding monkey or snake would be just as likely to 
