70 
THE PAN-PACIFIC ENTOMOLOGIST 
western Arizona deserts, since they surely must have the ability to avoid poisonous food 
plants indigenous to their own habitat. However, the fact that they fed on oleander and 
were apparently killed by it suggests that their avoidance behavior is specific to the set of 
plants native to the habitat rather than some kind of generalized behavior which would 
allow them to recognize oleander as a poisonous plant. Judging from the miniscule pro¬ 
portion of oleander in the total biomass of plants fed on by the total cicada population, it 
seems extremely unlikely that these cicadas would ever evolve resistance to oleander, 
even if the relevant mutant were to appear. 
Ackowlegements 
I thank Tom Moore for identifying the cicada and comments on the manuscript. This 
study was supported by grant number BMS 75-14268 from the National Science Founda¬ 
tion. — D. H. JANZEN, University of Pennsylvania, Biology, Philadelphia 19104. 
SCIENTIFIC NOTE 
Population increase of introduced Elaterids, Conoderus exsul and C. falli. (Coleoptera: 
Elateridae).— Since its interception at Alameda, CA. in 1937 the sugarcane wireworm 
Conoderus exsul (Sharp) has currently been recorded from 14 counties in California. The 
southern potato wireworm, Conoderus falli Lane first intercepted in 1963 near Palm 
Springs has been reported from 4 counties. To learn more of the build-up of these 
elaterids records were kept of adults trapped at a 15 watt survey type fluorescent black 
light, located at Riverside and at Olive, CA. (Orange Co.), about 30 miles from Riverside. 
Adults were collected daily or on alternate days during the months May to November 
1977. In the years 1974-76 inclusive the adults were collected between 9 and 10 p.m., from 
a suspended canvas at the top of which was placed a portable type black light of the same 
size and wattage as above. 
Table 1 shows that the regulation survey type trap used in 1977 was either superior to 
the hand method of recovering adults, or was an indication of the tremendous build-up of 
both species in the 4 year period of these studies. At Olive in the years 1974-76 catches of 
C. exsul adults increased gradually, a trend to be expected, whereas at Riverside there 
was but slight difference in numbers of adults collected annually. The sizeable increase 
in numbers of C. exsul adults trapped at both locations in 1977 is an indication that this 
species has become well adapted climatically to this area. 
The peak of C. exsul adult catches at both locations in 1977 occurred during July and 
August, a total of 30 and 37% were trapped at Riverside, respectively and 31 and 49% at 
Olive. 
Table 1.—Yearly catches of Conoderus exsul and falli adults at black light. Riverside and 
Olive, CA. 1974-77. 
C. exsul 
C. falli 
Riverside 
Olive 
Riverside 
1974 
286 
518 
436 
1975 
211 
1238 
440 
1976 
219 
1564 
401 
1977 
3106 
3652 
2289 
The Pan-Pacific Entomologist 54:70-71. January 1978 
