BIOLOGICAL NO IKS ON THE PARASITES. 35 



ecrobicoUis, which breeds in great abundance in the stems of the com- 

 mon road weeds Ambrosia trifida and A. psilostachya, at Victoria,Tex., 

 April 5, 1905 (1 female). In a personal letter dated August 30, L906, 

 Dr. Win. II. Ashmead writes of this species: " Eurytoma tylodermatis 

 Ajshm. is another similar case [referring to his remarks <>n Ceramby- 

 cobius, giveD later]. I have had several species of Eurytoma bred 

 by Hopkins, Marlatt, etc., from beetles, and I can only quote their 

 records. The genus seems to he primary and secondary as well as 

 phytophagous, unless we can find characters to still further subdivide 

 it generically." 



This parasite is quite abundant throughout the season and is a con- 

 tinuous breeder. The number of generations is probably Little less 

 than that of the weevil. There is but one individual to each host, and 

 the latter may be in the larval or pupal state when attacked. The 

 sexes are in the proportion of 29.1 per cent male and 70.9 per cent 

 female. The females are very much larger than the males. 



Proceeding in the same manner as for the preceding species it is 

 ascertained that the total developmental period is over 12 to 15 days, 

 that the larval plus pupal period is over 11 to 14 days, and that the 

 pupal period alone is at the minimum 6 days and maximum 13 days. 

 Judging from this last period, for which the figures are definite, it 

 may be safely said that the estimates for the larval and e^g periods 

 are very low. The increase in the length of the pupal period in 

 October is noticeable. 



The data upon the biology of Eurytoma tylodermatis are compara- 

 tively continuous from July 18 to October 19. In studying the length 

 of the various stages the same methods were used as outlined for 

 Microdontomerus. The only stage which could be definitely limited 

 as to the period of development was the pupal stage, which was found 

 to last from 7 to 8 days in the latter half of July, 6 to 9 days during 

 August, 7 to 9 days in September, and 11 to 13 days in October. 



The larvae of Eurytoma were described in the notes as smooth, 

 transversely lineolate, and with wrinklings at the sutures. The 

 pupae are white, pink-eyed, 'turning black toward maturity. They 

 may be easily distinguished, by the lateral compression of the abdo- 

 men and the straight venter, from the pupae of Catolaccus with their 

 dorso-ventra) compression and obtusely angulated venter. The 

 exuvium is cast in parts and is never found intact as in the case of the 

 other chalcidoids studied; the remains are yellowish transparent. 

 (See figure of pupa, PL I, fig. 1.) 



Secondary parasitism: One male was bred from material collected 

 August 9 at Trinity, Tex., and two males from material collected 

 September 19 at Waco, Tex., as secondary parasites in the cocoons 

 of Bracon mellitor. In each case the cocoon was isolated when first 



