THE MITES 99 



from their nests by the activity of the pests which the warmth of their 

 bodies creates. 



The Dermanyssus does not limit itself to birds, but may attack 

 mammals, including man, though these animals, being accidental hosts, 

 the invasion is usually limited in its extent and duration. Horses kept 

 in the vicinity of infested henhouses are likely to be tormented by the 

 mites, the Utter about stables so located affording a harbor to which 

 they readily migrate. 



The eggs are deposited in vast niunbers in the daytime retreats. 

 Under ordinary conditions about five days are required for the hatching 

 of the hexapodal larvse which do not wait for maturity to attack the 

 chickens. They may, however, remain for months without a host upon 

 which to satisfy their appetite for blood. Extremely prohfic, they 

 especially thrive upon filth, and large colonies may be found wherever 

 such material has collected. 



Effect. — Fowls suffer not only from the extreme irritation and an- 

 noyance of the attack, but additionally from the extraction of a consider- 

 able amount of blood. Prolonged infestation must essentially bring 

 about a progressive emaciation and weakening which may end in death, 

 young chicks especially being likely to succumb. In any event egg 

 production is retarded, and the chickens, in their unthrifty condition, 

 are unprofitable for marketing. 



Control. — Cleanliness and plenty of sunlight are especially antago- 

 istic to the Dermanyssus. The cleaning up measures set forth elsewhere 

 for the eradication of the parasites of the henhouse need not be repeated 

 here. Kerosene emulsion (page 48) is serviceable, but should only be 

 apphed after the entire interior has been stripped to the boards of every- 

 thing movable and all crevices, joints, and roost insertions exposed. 

 It is well to drench cracks and the ends of roosts with pure kerosene or 

 scalding water. The ends of roosts, before being replaced, should be 

 dipped in coal tar, and this spread along the roosts for about six or eight 

 inches from their supports in such manner that the mites will be obliged 

 to cross the tar before reaching the fowls. Pyrethrum powder, alone or 

 mixed with lime dust, should be shaken through the fresh nesting mate- 

 rial. The dust bath, as recommended in the treatment for lice, should 

 always be accessible. 



In order to insure continued freedom from the vermin it is necessary 

 that the control measures be repeated at least three times at intervals 

 of about ten days. 



Family II. Trombidiid^ 



Harvest mites; chiggers, or red bugs. Acarina (p. 94). — The body is 

 red in color and covered with bristles or fine hairs. The mandibles are 

 chelate; palpi prominent. The legs have six to seven segments pro- 



