REVISION OF STEEPSIPTEEA PIEECE. 17 



The parasites do not penetrate the vital organs of the hosts, but 

 adjust themselves between the organs and crowd these out of position 

 or crush them. The nourishment seems to be by osmosis — that is, 

 by absorption of the juices of the host, although this point is not defi- 

 nitely established. Sometimes the number of parasites becomes so 

 great that the host becomes seriously injured and death results. 



The location of the parasites in the body of the host is as a general 

 rule indifferent, although the males generally occupy the basal seg- 

 ments and the females the apical segments. These remarks are based 

 primarily upon a study of Polistes annularis. A notable exception 

 was found in Andrena crawfordi, in 92 parasitized individuals, of which 

 every parasite was located between the fourth and fifth segments. 



With Homoptera there seems to be more definite location for the 

 parasites, according to Perkins (1905). He treats this subject as fol- 

 lows: 



It is perhaps worthy of notice that the male puparia of the species of Halictopha- 

 gus(7), parasitic on jassids, pierce the dorsum or even the venter of the abdomen of 

 these leaf-hoppers, but the head of the female is always, or nearly always, thrust 

 through the pleura. On the contrary, in Elenchus and Deinclenchus, parasitic on 

 fulgorids, the male puparium (as well as the head of the female parasite) is exserted 

 from the pleural region only. 



In the case of the Halictophaginae we found only mature leaf-hoppers to contain 

 mature female parasites and puparia; but in the case of Elenchus ten uicornis the nymph 

 or adult delphacids will alike produce mature parasites of either sex. 



In the following pages are brought together definite statistics, pub- 

 lished and original, on the percentage of infestation of several species 

 and on the location of the parasites in the bodies of the host. 



POLISTES ANNULARIS Linnaeus. 



At Rosser, Texas, on September 23, 1905, Mr. F. C. Bishopp and 

 Mr. C. R. Jones, both of the U. S. Department of Agriculture, col- 

 lected two large nests of Polistes annularis, abundantly parasitized by 

 Acroschismus pallidus Brues. 



The nests contained, respectively, 1,575 and 1,212 cells, or a total 

 of 2,787 cells, from which at the time or by subsequent breeding 1,553 

 wasps were obtained. 



On these wasps the following data were obtained, as tabulated: 



1,311 male wasps, 1,052 unparasitized, 259 parasitized. 

 242 female wasps; 235 unparasitized, 7 parasitized. 



1,553 wasps; 1,287 unparasitized, 266 parasitized. 



84.4 per cent of the wasps were males, 15.6 per cent females. 



97.3 per cent of the parasitized wasps were males, 2.7 per cent females. 



80.3 per cent of the male wasps were unparasitized, 19.7 per cent parasitized. 



97.2 per cent of the female wasps were unparasitized, 2.8 per cent parasitized. 



82.8 per cent of all the wasps were unparasitized, 17.2 per cent parasitized. 



