36 



THE REDWOOD. 



brown beetle. Tliis beetle is one of the engraver beetles, so called on account of the 

 appearance of the system of burrows. The central tunnel is made in the sapwood 

 by the mother beetle, which deposits eggs at frequent intervals. The larvae hatch- 

 ing from these eggs bore off at right angles. When the beetles are numerous the 

 trees are frequently encircled, so that the food supply is cut off. The attack is 

 usually begun at the top of the tree, and extends downward from year to year. 



This family of beetles generally attacks trees that are not in a very liealthy condi- 

 tion, although when they become very numerous they take to healthy trees. Such 

 has proven to be the case with the Lawson Cypress beetle. Those trees which have 

 suffered most severely from drought lately have been most severely injured by the 

 pest, while those in the same locality which have been kept thrifty are in many 

 instances almost free. 



After these borers have once gotten into a tree there is no way in which they can 

 be killed without injury to the tree. Where the attack is severe the trees should be 

 cut down and burned during the winter while the insects are in their burrows. They 

 begin to eat their way out as early as March, although some appear much later; hence 

 the destruction should be done earlier than this. Trees only slightly affected need 

 not be destroyed, since by fertilization with Chile saltpeter and frequent watering 

 they ma}- be gotten into such a healthy condition as to Avithstand, and in a measure 

 resist, attack. Professor Hilgard has by this means saved some of his trees, which 

 were beginning to show marked signs of injury. Prompt measures shoulil be taken 

 against the insect, not only to save the trees attacked, but also to prevent the num- 

 bers from becoming so great as to cause them to spread to healthj' trees. 



Dr. Hilgard informs the writer that his experiments with Chile salt- 

 peter were ver3' successful indeed, and that he believes little harm 

 would result from the attack of this insect if the trees were kept in a 

 health}', vigorous condition. 



Early in September of this year the writer had an opportunit}^ to 

 make some additional observations on the habits of this beetle at Del 

 Monte and in the famous Monterey Cypress grove at Cypress Point, 

 Cal. These observations indicate quite clearlj^ that the Monterey 

 Cypress is the original food plant, and that the common use of this tree 

 for hedges and ornament in private grounds and parks throughout 

 western California has ena})led the beetle to extend its range from its 

 original restricted home, and thus to acc^uire the habit of attacking 

 other species of Cypress and the Redwood. This change of habit and 

 extended range of distribution, as has been demonstrated by many of 

 our worst insect pests which have come from other countries and other 

 sections of our own country, involves variation in normal habit, and 

 even in structure, which renders a species that is comparatively harm- 

 less in its original home most destructive under the influence of new 

 environments. 



An examination of the Cypress grove showed no sign that this 

 beetle had attacked standing trees, although it was found to be 

 exceedingly common in the liark of broken branches and storm-felled 

 trees. The natural enemies of the liroods occurred in great num])ers, 

 and up to the date of writing the number of adult parasites which 

 have emerged from sections of branches placed in breeding jars has 

 been exceedingly large. 



