THE MONTHLY BULLETIN. 113 



THE DISTRII5UTI0N OF CALIFORNIA INSECTS. I. 



E. O. EssiG, University of Califoriii;i, Berkeley, California. 



Uuder the above heading the writer desires to present from time to 

 time a series of maps showing as accurately as possible the known 

 distril)ution of soiiu^ of the coinnion cconninic insects of this State. In 

 considering the subject from this viewpoint the economic insects may 

 be placed into two large groups. In the first group might be included 

 the native insects which are abundant throughout the State, such as 

 the western 12-spotted cucumber beetle, Diahrotica soror Lee, the alfalfa 

 semi-looper, Fhytometra calif ornica (Speyer), the muck or carrot beetle, 

 Ligyrus gibhosus DeGeer, etc., and those introduced insects which have 

 become widely distributed and persist in large numbers, like the black 

 scale, Saissetia olece (Bern.), the woolly apple aphis, Eriosoma lanigera 

 (Hausm.), the imported cabbage worm, Fontia rapce (Linn.), the San 

 Jose scale, Aspidiotus perniciosus Comst., etc. The common occurrence 

 of such insects is so generally known that it is not thought necessary to 

 include this group at all. In the second group might be placed the 

 native insects which are limited in their distribution to more or less 

 definite areas, and have become quite serious pests in those districts, 

 like the California peach borer, jEgeria opalescens H. Edw., the pear 

 thrips, Tceniothnps pijri (Daniel), the California oak moth. Phryganidia 

 calif ornica Pack., etc., and those introduced insects which, because of 

 prevention, lack of time or some other reasons, are still confined to small 

 or scattered areas, such as the citrus white fly, Dialeurodes citri (R. & 

 H. ) , which has been persistently fought to blot out the infested districts 

 and to prevent further spread; the purple scale, Lepidosaphes heckii 

 (Newm.), which likewise has been constantly fought; the Argentine ant, 

 Iridomyrmex humilis Mayr, which will probably continue to spread as 

 rapidly in the future as in the past if let alone, etc. Much of the state 

 and county horticultural legislation has been concerned with the mem- 

 bers of this group and it is also this group that the writer wishes 

 to include in this series of distribution maps. In doing this he realizes 

 the difficulty of securing complete and exact data, and takes this oppor- 

 tunity to invite the most rigid criticism in the form of corrections and 

 additions. In some cases quite large areas may be marked on the maps, 

 when in reality the infestation consists of a number of small places, 

 and it has been impossible to definitely ascertain all of the individual 

 localities. In all cases the idea is to give the general infested area 

 rather than the numerous small isolated places, so as to conform with 

 the custom of quarantine regulations covering such situations. 



The data has been compiled from many sources, including observa- 

 tions and printed matter from the officials of the State Commission of 

 Horticulture, the University of California, the United States Depart- 

 ment of Agriculture, the County Horticultural Commissioners and 

 others, as well as the observations of the writer. 



