CONTRIBUTIONS 



TO THE 



LARVAL HISTORY OF PACIFIC COAST COLEOPTERA. 



By J. J. RIVERS, Curator of the Museum, University of California. 



The study of systematic entomology affords the student but a dim idea 

 of what insects are noxious and what are innoxious. The distinctive char- 

 acters upon which the systematic entomologist builds classification need 

 not be and generally are not the characters of prime importance to the 

 economic entomologist. The names of many of the groups of Coleoptera 

 afford a slight generalized description which is often misleading. In the 

 present state of entomologic science, where systematic method is given 

 precedence over the biologic, it is dangerous to attempt to make a general 

 statement of the habits of a single genus, and impossible to generalize the 

 habits of a group or family. 



The most valuable contribution to the life history of American insects 

 which is generally accessible is Dr. Packard's " Insects Injurious to Forest 

 and Shade Trees." * In his introduction , the author states that this work 

 is purely tentative, and designed^) elicit the results of the observations of 

 students of economic entomology. It is on that account that I feel at lib- 

 erty to comment upon or question certain of Dr. Packard's statements. 



On page 118, op. cit: Prionus laticollis, Drury, is noted as injurious to 

 the poplar. If Prionus destroys living trees in other parts of America, it 

 has no such destructive habit in California; in fact, the charge against 

 borers that they destroy trees is a very old one, but by no means substan- 

 tiated by my own observations. P. Californicus goes through its trans- 

 formations in the roots of oaks, but these roots were dead in every case 

 observed by me, and usually belonged to stumps whose trunks had been 

 felled years before. Last year I bred several from the decayed part of an 

 old oaken chopping block. In fact, Dr. Packard himself throws some 

 doubt upon the destructive habit of P. latiocollis, for in his note he quotes 

 the report for 1872 of Prof. S. J. Smith, Entomologist to the Connecticut 

 Board of Agriculture, as follows: " I have noticed it in logs of poplar, bass- 

 wood, and oak, and in the trunks of old, decaying apple trees." 



On page 137, op. cit., is the following: "We have found Buprestid and 

 Longicorn borers in a dead sweet gum tree." The caption at the head of 

 the page, " Insects Injurious to the Sweet Gum," seems designed to lead to 

 the inference that these borers killed the tree. But my observation is that 

 the larvae of insects of the two families noted feed only on dead wood. 



Again, on the same page (137), Ptilinus basalis and Micracis hirtella 

 are listed as injurious to the California bay. These species are both found 

 in Berkeley, and I have observed their habits for the last seven years, and 

 as a result of such observation I am in a position to assert that they bore 

 into the twigs of the tree mentioned only when dead, dried, and decaying. 



On page 71, op. cit., we find a figure of Oncideres cingulatus in the act 

 of girdling a hickory twig. In connection with this insect we meet with 



*U.S. Entomological Commission, JMfetm V^Sington, 1881. 



