SO MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
rat fleas and those on some ground-inhabiting rodents are especially 
to be avoided because of the danger of their transmitting bubonic 
plague. Buishopp (37) discussed these insects and methods of control. 
Fleas are easily controlled about premises by preventing their breed- 
ing. This is done by treating the floors and bedding, or - other places 
frequented by animals, with DDT dust. Inside the house, liberal ap- 
plications of DDT or pyrethrum sprays or dusts are effective. Do- 
mestic animals should be kept free of adult fleas by weekly or bi- weekly 
applications of derris powder: 
DDT powder is also effective and can be safely used on dogs but 
not on eats. 
THE BRISTLETAILS 
OrpER THYSANURA 
and 
THE SPRINGTAILS 
ORDER COLLEMBOLA 
Certain small and often very active insects are frequently found in 
great numbers congregated under stones or bark of dead trees and 
stumps or in old damp buildings around lumber camps. They are 
bristletails and springtails. They are very primitive insects without 
wings and with chewing mouth parts. In the springtails the third 
and fourth abdominal segments are provided with a springing ap- 
paratus. On warm days during the winter some species often appear 
in enormous numbers on the surface of the snow. 
Although often abundant, these two orders do not cause any damage, 
but they are of economic importance to the forester in that they 
play an important role in the reduction of leaf litter on the forest 
floor and aid in the formation of humus. More detailed information 
on these insects may be found in Jacot (253) and in Back (8). 
THE THRIPS 
OrpeER THYSANOPTERA 
The thrips are minute insects, often of active movements, either 
wingless or with four slender wings fringed with hairs. They have 
mouth parts fitted for sucking, and legs ending in a bladderlike tip. 
These tiny insects are extremely abundant at times on all kinds of 
flowers, and some species do considerable damage to cultivated plants. 
causing characteristic malformation or unhealthy appearance of the 
parts affected, and at times transmitting certain virus diseases ot 
plants. They are rarely injurious in the forest. although Liothrips 
Sey ae ‘Hood caused extensive curling of chestnut oak leaves In 
northern New Jersey in 1937, and some occasionally are injurious in 
the nursery. Some forms are abundant on the pollen-bearing flowers 
and attract the attention of those collecting pollens. Gnophothrips 
piniphilus Cwtd. occasionally causes much injury to pine seedlings 
in nurseries. Other forms are so abundant in midsummer that they 
become a nuisance by crawling over the skin and occasionally biting 
man. For control measures see page 53, formula 4. 
