330 ' JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



vigorous a condition as possible. This will not prevent an attack 

 but it will help the plant to overcome it. Most attacks in California 

 and the southwest start from what appears to be sunburns. Most 

 of the smaller fruit and shade trees are attacked on the trunk. Weeping 

 trees are attacked on the topmost branches which the leaves do not 

 cover. Any kind of a protection which will keep the sun from 

 reaching the exposed bark is good. Once the plant is infested, as is 

 indicated by the wet spots on the bark, the best thing to do is to care- 

 fully cut away the dead bark, kill the borer and cover the wound with 

 a good dressing such as coal tar or liquid asphalt. 



LAC-PRODUCING INSECTS IN THE UNITED STATES 

 (HEMIPTERA; COCCIDiE) 



G. F. Ferris, Stanford University, Cal. 



Lac (better known as "shellac") is an insect product. It is formed 

 as a secretion from the dermal glands of certain species of Coccidse 

 belonging to the genus Tachardia. Species of this genus occur in 

 Asia, Africa, Australia and North and South America, but at the 

 present time only certain species found in Asia are utiHzed com- 

 mercially. Lac is a very important article of commerce, being used 

 as a basis for varnishes, as an insulating material in the electrical 

 industry and for other minor purposes. 



In view of the conditions existing during the late war it seemed that 

 the possibility of developing a domestic source of supply of this sub- 

 stance should not be neglected. While it was fully realized that this 

 possibility was remote, there were some grounds for believing that it 

 existed. 



We have three or four species of the genus Tachardia in the south- 

 western part of the United States. One of these species, Tachardia 

 larreoe (Comstock), occurs in sufficient abundance to have attracted a 

 considerable amount of attention and it has several times been suggested 

 that the commercial recovery of the lac might be possible. Some 

 encouragement has been lent to this behef by the fact that the host 

 of this species is one of the most abundant and most widely distributed 

 shrubs of the so-called "desert regions" of the United States. This 

 plant is the "creosote bush," formerly known as Larrea mexicana, now 

 called Covillea glutinosa. 



Some of the reasons for believing that the matter was worthy of 

 investigation may briefly be summarized. 



Before the insect in question had received a scientific name. Dr. J. 

 M. Stillman, later head of the Department of Chemistry of Stanford 



