234 



THE AGRICOLTURAL NEWS. 



July 23, 1910. 



INSECT NOTES. 



THE ACARINA OR MITES. 

 PART III. 



GAMAsiDAE. This family includes, among many other 

 forms, the poultry mites, which in Barbados at least, are com- 

 monly known as ninibles. This group of mites is character- 

 ized by the small pincer-like arrangement of the mandibles. 

 The individuals are very minute in size, and inconspic- 

 uous in colour. The poultry mite, which may be taken 

 as an e.xampie of the family, is Dermnni/ssns yallinae^ 

 a species of world-wide distribution as a pest of domestic 

 fowls. The normal colour is light-biown or whitish, but 

 full-fed individuals are reddish, from the blood with which 

 they are engorged. These mites hide in the vicinity of 

 fowl roosts during the day, and come out at night and 

 attack the fowls. When they occur in enormous numbers, as 

 sometimes happens, the effect on the poultry is so severe as 

 to justify including this among the most serious pests of the 

 poultry yard. They very seriously affect the condition of fully 

 grown fowls, and have been known even to kill out an entire 

 brood of newly hatched chicks. Cleanliness is one of the 

 precaution.s to be taken against ninibles. The perches should 

 be made detachable so that 

 they may be taken out and 

 carefully washed, and the 

 house or pen should be clean- 

 ed by spraying with kerosene 

 emulsion, or by the use of 

 lime-wash, kerosene emulsion 

 probably being the more 

 effective on account of its 

 greater penetrating power, 

 which enables it to get^into 

 the very small crevices where 

 the mites are in hiding. 



The houses and perches 

 may also be kept clean by 

 the use of boiling water, 

 kerosene, benzene, or ga.so- 

 lene The free use of lime 

 is also beneficial, and a good dust bath for the fowls helps 

 greaily in repelling the attacks of their nightly visitors. 

 It is of advantage also, where the construction of the house will 

 permit, to apply coal tar to the ends of the perches, after these 

 have been cleansed, in such a way that the mites will have to 

 cross it in order to reach the f<:iwls. As long as the tar 

 remains soft on the surface, the mites will be unable to get 

 across. The use of sulphur or tobacco stems in the nests of 

 sitting hens will also be found valuable, and in each island of 

 the West Indies certain plants are commonly credited as hav- 

 ing repellant properties toward mites and other pests Among 

 these may be mentioned the leaves and twigs of the wild olive 

 (Bontia dajAnoides) and of a species of Jatropha. 



rxoDiDAE. This family includes the ticks, the largest 

 of all the mites. They are of very great importance because 

 of their parasitic habits and because, in the case of many of 

 them at least, they are intermediate hosts in the life-history 

 of parasitic diseases, some of which are verj' serious in the 

 case of domestic animals. 



The ticks are provided with a very formidable mouth, 

 well adapted to their piercing and .sucking habits. They are 

 covered with a tough, leathery skin, wliich in the front part 

 of the body forms a hard protecting shield; the hinder uart of 

 the body is capable of considerable distention, and fully fed 



Fig. 34. Cattle Tick. (Female on left : male on right.) 



individuals are much larger on this account than unfed ones, 

 in the same stage of development. 



The cattle tick, or Texas fever tick, is perhaps, in point 

 of amount of damage done, the most important of all the 

 ticks. In the Southern States of America, this has 

 caused losses in the cattle industry estimated at as much as 

 •$40,000,000 per annum. The injury to cattle arising from 

 this pest is estimated to be of three distinct kinds; firstly, the 

 tick is a direct parasite, weakening the animal by loss of 

 blood; secondly, the inflamed areas resulting from tick attacks 

 often attract the screw worm Hy, Chiysomyia mace/laria; 

 and thirdly, it is a carrier of the disease mentioned. 

 In cases of gross infestation, it has been estimated that as 

 much as 200 lb. of blood may be drawn from an animal in 

 the course of a season, but the greatest loss sustained by the 

 cattle industry is that due to the ravages of the disease, 

 which results from the presence in the blood of a proto- 

 zoan parasite, Piro2ilasma hiyemimum, which under natural 

 conditions, can only be transmitted by the bite of an infected 

 tick, as far as is known. 



Although several species of ticks are liable to be found 

 feeding on cattle, only one species in each district is known 

 as the carrier of the parasite causing Te.vas fever. In the 

 United States this is Boophilus annulatus, or Maraaropus 

 aimidatiis (Fig. 34), as it has been called recently. As the 



life-history and habits of 

 this tick have been carefully 

 studied, it may be taken as 

 an example of the family. 

 The cattle tick is red- 

 dish in colour, somewhat 

 flattened, becoming greatly 

 distended when fully fed. 

 The life-history includes 

 four distinct stages: the 

 egg, the larva, the nymph 

 and the adult. The eggs 

 are laid on the ground, where 

 the}' hatch after a varying 

 period of time, according to 

 temperature, or the extent 

 to which moisture is present. 

 The larvae are very small, 

 active creatures, capable of existing for many days, or 

 even weeks, without taking food. Immediately on hatching, 

 these larvae, which in some places are called seed ticks, 

 and in others grass lice, climb up on grass or weeds, where 

 they await some passing animal, which would serve as 

 host. When a suitable animal conies along, they attach 

 theniselve.s, and almost immediately begin feeding. After 

 a short time, the larval skin is cast, and the six-legged larva 

 transforms to the eight-legged nymph, which in its turn 

 becomes fully fed, and changes into the adult condition. 

 At this time, the sexes are developed, the males being 

 somewhat smaller than the females. After mating, the males 

 soon die, and the females continue feeding until they are fully 

 fed, in which condition they are many times the original size. 

 As soon as the female has become fully fed, she releases her 

 hold and drops to the ground, for the purpose of depositing 

 eggs, which often number several thousands. The period of 

 egg-laying marks the end and beginning of one life-cycle. 

 The length of time occupied by this varies greatly, accord- 

 ing to climatic conditions, a period of from six to ten 

 months being required in warm weather, and a much 

 longer one in the cold season. In certain of the West 

 Indian islands, it is likely that the dry season has the 

 effect of retarding the development of ticks in a manner 



