372 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
of the host, leaving a large exit hole usually at the junction of the meta¬ 
thorax and abdomen. The hopper is killed after the larva emerges. 
After escaping from its host, the larva buries itself beneath the soil and 
pupates. At Spreckels the flies issued after remaining in the pupal 
stage for a period of 22 days. 
The female of Gonatopus contortulus is a wingless, ant-like parasite of 
the family Dryinidae. Mr. S. A. Rohwer determined “the two parasites 
bred from the beet leaf hopper as Gonatopus contortulus Patton, and 
Labeo sp. n. He says that this male is no doubt that of the above female. 
There is much confusion about the males of Labeo, of which no female is 
known. Some male Labeo are males of females described in Gonatopus 
and Dryinus.” 
The ant-like female is a very active creature, capturing and partly 
devouring a large number of hoppers. A single parasite emerging in a 
cage will kill most of the leafhoppers, but it is only in an occasional leaf- 
hopper that an egg is deposited. The presence of the parasite in its later 
development can be determined by the external dark brown sac in the 
nymph or beneath one of the wings in the adult leafhopper. After the 
parasitic larva quits its ho£t, it spins a white cocoon (length 3 mm. 
width 1.5 mm.) on the foliage of the saltbush or beet leaf. Forty days, 
after spinning its cocoon, the wingless parasite emerged on October 24, 
1914 at Spreckels. 
Percentage of Parasitism. —We (6) have published a paper on the 
natural enemies of the beet leafhopper and in 1913, about 3.2 per cent 
and in 1914, about 33.6 per cent of the leafhoppers collected in beet fields 
were found to be parasitized by P. vagabundus , P. industrius and G. 
contortulus. 
During 1918-1920, a comparison was made of the percentage of 
parasitized beet leafhoppers collected on the plains and foothills with 
those captured in the cultivated areas of the San Joaquin Valley. 
Records obtained by dissecting the adults are more reliable than those 
secured by breeding the parasites, since a high mortality of the insects 
occurs in the breeding jars. The average percentage of parasitized 
adults of various broods by Pipunculus and Gonatopus is indicated in 
Table 1. 
The weak point in the parasitism of the adults occurs on the plains 
and foothills. Dissections show that only those winter brood adults, 
which are parasitized by a tiny larva, fly to the foothills resulting in an 
extremely low percentage of parasitism of the spring brood. It 
is evident from Table 1, that the percentage of parasitism gradually 
