3o6 Journal of Agricultural Research voi. iv, No. 4 



LABORATORY EXPERIMENTS 



Several of the adult parasites, captured and confined with the eggs of 

 the asparagus beetle in the laboratory, were noted shortly afterward, 

 ovipositing and feeding on the beetle eggs. A few days later all eggs 

 of Crioceris asparagi which had not been eaten by the parasites had 

 hatched. At the time this could not be accounted for, since this insect 

 had previously been considered an egg parasite and many of the eggs 

 which hatched were known to have been subjects of oviposition. None 

 of the young beetle larvae that hatched from these eggs were carried 

 through to maturity. The cause of their death appeared to be a lack 

 of proper food. 



On the first day that the parasites were observed in the field, Mr. 

 Russell collected nearly mature larvae of the asparagus beetle from volun- 

 teer asparagus plants in a field which had been planted to asparagus at 

 some prior date. The larvae were taken to the laboratory and placed in 

 rearing cages that they might form their cells. A few days later, while 

 the cocoons were being examined, six small whitish larvae were found in 

 one cocoon. Some of these larvae at a later date pupated, but died 

 before the adult stage was reached, so there was no certainty that these 

 v/ere the larvae of T. asparagi. 



About July 10 the writer collected asparagus-beetle larvae from a field 

 in which parasites had been previously noted in abundance and, bringing 

 them into the laboratory, supplied them with food and confined them in 

 vials without earth. 



Upon examining the vials on July 24 it was seen that five beetles had 

 emerged and in one vial there were three small pupae. In another vial 

 was a small whitish larva similar to those which Mr. Russell had previ- 

 ously taken from a beetle cell. 



The three pupae were placed in a separate vial, and on July 30 and 31 

 they emerged as adults, which were later identified by Mr. Crawford as 

 T. asparagi. 



On June 20 the writer dissected the egg of T. asparagi from the aspara- 

 gus-beetle egg, and the peculiar life history of this parasite was at length 

 established. 



For nearly two weeks after the parasites were first observed in the field 

 they were to be found in considerable numbers, after which they suddenly 

 disappeared; by June 24 none could be found. During the latter part 

 of July they again made their appearance in the field but were much 

 harder to locate, since the entire asparagus field by this time had been 

 allowed to grow, and, in consequence, the parasites were scattered over a 

 much larger area than before. 



On August 5 the first parasites of a second generation were captured in 

 the field and brought into the laboratory. They were confined in large 

 vials and each day were given a fresh supply of beetle eggs, which were 

 treated as noted before. On hatching, the beetle larvae were removed to 



