June, ’24] 
severin: beet leafhopper enemies 
369 
Tiphia cocoons was likewise reduced 95 per cent; while the number of 
Popillia larvae was increased 94 per cent. It might at first be assumed 
that the Ochrosidia larvae were reduced entirely by parasitism. This of 
course was the largest factor causing the reduction; but disease and 
winter kill also helped in the decrease as was before mentioned. 
Conclusions 
It has been observed during the past several years that the larvae of 
Ochrosidia immaculata became very numerous on a golf course in the 
vicinity of Moorestown, N. J. Within the past two years, the abun¬ 
dance of the larvae has been reduced approximately 93 per cent by a 
native species of fossorial wasp belonging to the genus Tiphia. In the 
same manner the parasite increased in numbers and as the abundance 
of the host was reduced the numbers of the parasite decreased nearly 
95 per cent. At the same time a related Scarabaeid, Popillia japonica, 
became very numerous in the same locality. Under conditions in the 
field only two Popillia larvae were found to be successfully parasitized 
by the native Tiphias. Experiments which were conducted indicated 
that the female Tiphia deposited her eggs, by preference, on the Ochro¬ 
sidia rather than on Popillia larvae. The life histories of Ochrosidia 
immaculata and Popillia japonica are similar in this region, but the former 
larvae are larger than the latter, when both are full grown. Neverthe¬ 
less during the latter part of August, when the Tiphias are present, 
many Popillia larvae have reached the third instar in their development; 
while many Ochrosidia larvae are in the second instar and are smaller 
than the Popillia larvae which have reached the third stage. 
It is evident that, at present, this species of Tiphia is selective in its 
preference for its native host; but since it is possible for some indi¬ 
viduals to develop successfully on the Popillia grubs, it is possible the 
Tiphias may develop a strain which will become parasitic on this in¬ 
troduced species. 
NATURAL ENEMIES OF BEET LEAFHOPPER (EUTETTIX 
TENELLA BAKER) 
By Henry H. P. Severin, Ph.D., California Agricultural Experiment Station 
Abstract 
Among the natural enemies of the beet leafhopper (Eutettix tenella Baker) are a 
large number of predaceous insects which prey upon the nymphs and adults. Seven 
species of egg parasites, two species of Pipunculus flies, a Dryinid and a hair-worm 
were bred by various entomologists in California. The percentage of parasitized 
