THE MONTHLY BULLETIN. 



ARACHNIDA (Class). 



SPIDERS AND MITES. 



^''r^'^'v^-^ 



Because of their economic importance we have thought it best to in- 

 clude here the common injurious mites of California, even though they 

 are not insects. As pointed out in the general classification, mites 

 usually have eight legs and have the head and thorax united. Some 



species, however, especially the 

 blister mites, have only four legs, 

 while the young red spiders have 

 six legs before the first molt. 



All forms feed by piercing the 

 plant tissues and extracting the 

 juice. They multiply very rap- 

 idly and thus are capable of 

 much damage. 



The winters are usually passed 

 in the adult stage, under buds 

 and bark scales. As soon as the 

 first leaves appear the mites 

 begin work. The eggs are laid 

 singly on the outside or inside of 

 the plant tissues, or in clusters 

 upon the bark ; in the latter case 

 they may be deposited around 

 the buds, some time before they 



begin to open. The young de- 

 velop very rapidly and are soon 

 capable of bringing forth new 

 broods. Tlie breeding continues 

 throughout the summer — t h e 

 greatest number of mites being evident during the hottest and dryest 

 weather. Cold, damp weather seems to retard all activities. 



Fig. 5. — Mite eggs deposited around a bud. 

 Greatly enlarged. (Original.) 



Control. — The control of mites has been no little task and con- 

 siderable work has been done with exceedingly satisfactory results. 

 Mites are generally controlled either by the application of dry flowers 

 of sulphur alone, finely powdered dehj^drated lime and flowers of sul- 

 phur in equal proportions, by hand or with a blower, or a two per cent 

 solution of commercial lime-sulphur wdth spraying machines. A late 

 development in the control of mites on truck crops has resulted in the 

 discovery by the United States Department of Agriculture of a flour 

 paste, made by mixing four pounds of flour in one hundred gallons of 

 water and adding one gallon of lime-sulphur solution. This is applied 

 as a spray. 



