4 FARMERS’ BULLETIN 683, 
mer probably the average longevity of the human flea without food 
is about two months, of the dog flea somewhat less, and of the stick- 
tight flea still less. 
ABUNDANCE OF FLEAS IN RELATION TO SEASON, CLIMATE, AND 
OTHER CONDITIONS. 
In the northern part of the United States nearly all fleas pass the 
winter in the immature stages, while in the more southern latitudes 
some of them are present on hosts throughout the winter months. 
In general, however, these insects are never as abundant during 
winter and spring as they are in summer and fall. 
Rainfall and the amount of moisture in the atmosphere have much 
to do with flea breeding. As a rule rainy summers are productive 
of outbreaks of fleas, and extremely hot, dry weather tends to check 
their breeding. This condition is brought about by the fact that 
the larva and pupa require a certain amount of moisture for suc- 
cessful development, and the adults also live longer when there is 
a proper degree of moisture present. It is not intended to convey 
the idea that fleas require very moist places in which to breed. As 
a matter of fact, excessive moisture in the breeding places is as detri- 
mental as excessive dryness. 
It is common knowledge that fleas occur in greatest abundance in 
sandy regions. This is explained by the fact that the sand maintains 
a more uniform moisture condition and thus permits the immature 
stages of the flea to develop with greater success. The sand also 
offers some protection to the adults and renders heavy rains less 
destructive to all stages of the flea present on the soil. 
FLEAS AS PESTS IN THE HOUSEHOLD. 
As has been pointed out,' in the eastern part of the United States 
the dog flea is the species of greatest importance as a household pest. 
Many instances have been brought to the attention of the Bureau of 
Entomology in which houses, particularly those vacated for some time 
during the summer months, have been found to be literally overrun by 
these pests. 
In portions of the South and West the human flea (figs. 8 and 4) 
is the one primarily responsible for house infestations. Although 
the host relationship of these two species is somewhat different, the 
same methods of control are applicable, for the most part, to both. 
1 Howard, s. O. House Fleas. U. S. Dept. Agr., Bur. Ent., Cir. 108, 4 p., 2 fig., Feb. 
11, 1909. 
