250 



THE AGRICULTUKAL NEWS. 



AuousT 6. 1910. 



INSECT NOTES, 



THE ACARINA OR MITES. 



PART IV. 



ixoDiDAE {continued). !Man}' remedial measures have 

 been tried for the control of ticks, and washes and other 

 applications have been advised for their destruction. In the 

 West Indies, the practice of picking or scraping ticks from 

 infested animals is often resorted to, but this method is 

 attended with serious disadvantages. The construction of 

 the mouth parts of the ticks gives them such a .secure hold 

 on the skin of the host, that if an attempt is made to pick off 

 the tick, the body often separates, leaving the head attached. 

 This is obviously a wrong proceeding, especially if there are 

 many ticks picked off in this way, for the mouth parts of each 

 form a point of irritation, even after blood-sucking ceases. 

 When the ticks are scraped off it also results in serious injury 

 to the skin of the host, since this practice causes the pro- 

 duction of a great number of open wounds, which may be 

 infected by any disease-producing organism, or even by large 

 insects such as the screw worm. 



The use of solutions containing soap, oil, sulphur, or 

 arsenic has been extensively tried, and they have been 

 applied by means of a sponge or brush, where only a few 

 animals have had to be treated, and, by means of dipping 

 tanks, when used in dealing with large herds. Perhaps the 

 most satisfactory of all methods for the control of the Texas 

 fever tick is that known as the ' pasture rotation ' system, 

 which within the last few years has been put into practice by 

 entomologists in certain of the Southern States. (See A(/ri- 

 cultural Xeivs, Vol. IX, p. 157.) 



The value of this method has been fully demonstrated 

 by trials on large areas in the cattle districts of Louisiana and 

 Tennessee. This S3'stem is based on an intimate knowledge 

 of the life-history of the cattle tick in those localities. The 

 following general outlines will serve to illustrate the principle 

 involved. This method depends for its .success, in the first 

 place, on the fact that the cattle tick is able to live only on 

 a suitable host, and secondly that the ticks do not of them- 

 selves travel far in search of food. 



An arrangement is made by means of which the cattle 

 may be changed from one enclosed i)asture area to others, so 

 that each pasture will be occupied by cattle for a definite 

 period at a certain time in the life-history of the tick. For 

 instance, if the animals are removed from the land on which 

 they have been pastured before the eggs begin to hatch, the 

 entire herd of cattle should be practically free from ticks, but 

 in order that the eradication of ticks should be complete, the 

 herd should be examined later, and removed again to another 

 tick-free pasture, when there has been sufficient time for the 

 few ticks which may be on the cattle to have completed their 

 life-cycle, and to have reached the fully-fed stage. 



By having four such enclosures, cattle ought to be ren- 

 dered tick-free within a year, and by that time the enclosure 

 which was first used should be free from ticks; for all the larvae 

 which hatched from the first deposit on this land will have 

 starved for want of a proper host. The time required for the 

 eggs to hatch, and the young to die of starvation, varies con- 

 siderably, and observation would be necessary in special dis- 

 tricts to establish the exact periods which would give the 

 desired results of this rotation .system. Sufficient time should 

 also be allowed before stock is returned to any of the pastures 

 on which this method is being carried out. 



In the United States, the time required for the complete 

 period, from the attachment of the seed tick to the dropping 

 of the adult, is frota twenty-one to fifty-eight days. The time 

 required for the adults to commence egg-laying after dropping 

 ranges from two to forty days, averaging in summer three or 

 four days. Egg-laying requires six to seventy days, averaging 

 ten or eleven days in summer. The time required for the 

 eggs to hatch varies from seventeen to forty-four days in 

 summer to over one hundred and seventy in the winter .season. 



In the West Indies, the cattle tick is Maryarojius annu- 

 latus aiixt>a/is, but several other species occur. The gold 

 tick oi Antigua. istr^AmUi/oiiinin iiai'teijatiini; this also attacks 

 cattle. Other species of ticks attack a great variety of hosts, 

 including even cold-blooded animals, such as toads and lizard's 



The fowl tick (An/as persicns, var. Qiimiatus), which 

 also occurs in the West Indies, differs in its habits from 

 the cattle tick. It hides during the day, and feeds on 

 the fowls at night. It is a large, flat, greyish tick, which 

 hides in crevices in and about the poultry house, in the same 

 manner as the nimbles, and consequently the same methods 

 of preserving the cleanliness of the house as were suggested 

 for the poultry mites should prove effective in controlling 

 the fowl tick. 



TYEOGLYPHIDAE. This family of mites is very impor- 

 tant from an economic point of view, and includes a large 

 number of species. The individuals are very small in size 

 and inconspicuous in their colour, and as a result, have often 

 been overlooked. On this account, the injury caused by them 

 has often been attributed to insects, which happened to be pres- 

 ent, and which, because of their larger size, have been more 

 conspicuous. They breed very rapidly, and thus more than 

 make up for their small size in the amount of damage which 

 they are able to do. They attack a great variety of sub- 

 stances, among which may be mentioned stored foods such as 

 cheese, flour, sugar, ham, and similar materials; hair in 

 furniture, mattresses and pillows; many drugs, seeds, bulbs 

 and roots of plants; and entomological and other museum 

 specimens. 



The mites of this family are soft-bodied, light-coloured, 

 and without tracheae; there are generally no eyes, and there 

 is often a distinct suture between the cephalothorax and the 

 abdomen. 



The transformations of the Tyroglyphidae are very 

 remarkable. All the species of mites of this family lay eggs 

 often of a large size, from which six-legged larvae hatch. At 

 [he first moult, an eight-legged nymph is developed, and the 

 further transformation may be similar to that in ticks. On 

 the other hand, a form is sometimes developed which is 

 known as the Hypopus stage. At one time, mites at this 

 state of develo|iment were supposed to be of a distinct species, 

 to which the name Hypopus was given. In this, the mite 

 differs very greatly from the octopod nymph from which 

 it develops. Its body is hard and chitinous, there is no 

 mouth orifice, nor distinct mouth parts; the legs are short 

 and not fitted for walking. On the ventral surface of the 

 body there is a specially developed area provided with 

 sucking discs, by means of which the hypopus is able to 

 attach itself to an insect, or other animal, for the pur[)Ose of 

 being trans|)orted to another locality. This stage seems to 

 be an especial adaptation for the purpose of migration, and is 

 remarkable, in that the efficiency of this mode of tran.sporta- 

 tion is entirely dependent on the movements of some other 

 creature. If successful in finding a suitable locality, the 

 hypopus is capable of moulting again to the form of an 

 eight-legged nyittph, which feeds and develops into the adult 

 condition. 



