REVISION OF STREPSIPTERA PIERCE. 39 



3. The enmity of ferocious hosts may result in the death of some 

 males, as is evidenced by Hubbard's records of Polistes (americanus) 

 crinitus. 



4. An accidental event was noted by Mr. Dury of a male breaking 

 its pupa-case and emerging into the body cavity of the host, where 

 it died. 



5. Fungus attack, in the case of Homoptera, following the exit of 

 a male parasite means death to the remaining parasites. 



6. Perez noted a case of the exclusion of a parasite, which had 

 forced its cephalothorax through the pellicle of the pupa at the time 

 of transformation. 



7. The sex of the host in a measure determines the mortality of 

 the parasites. In the case of Polistes at least the males do not 

 hibernate, while a fair per cent of the females do. By a glance at 

 the paragraphs on extent of parasitism it will be noted that in the 

 autumn the greatest per cent of the parasites were found in the male 

 hosts and that not more than 1 per cent of the female parasites 

 could be expected to exist through the winter, as only such hosts 

 as contained females alone can as a rule stand the rigor of the winter 

 season. (See Polistes annularis on pp. 17-20.) 



4. BIOLOGY OP THE HOST AS INFLUENCING THE BIOLOGY OF THE PARASITE. 



1. Biology of the host. 



a. In order to invite attack the host must be in the larval state as 

 demonstrated by Saunders (1852) with Polistes larva?. 



b. The development of host and parasite is generally parallel, the 

 exsertion of the puparium of the parasite occurring very shortly 

 after maturity, and being followed in a few days by the exit of the 

 adult. This point will be discussed more fully under the biology of 

 the male parasite. In Homoptera, however, the reverse may often 

 occur. Perkins (1905) writes: 



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

 mature female parasites and puparia, but in the case of Elenchus tenuicornis the nymph 

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



2. Social economy of hosts. 



The economy of the parasites is directly related to the economy of 

 the hosts. It is somewhat remarkable that among the latter are found 

 very nearly all of the important conditions of social economy known 

 among insects. As the general subject falls under several distinct 

 heads, the exact bearing on the present problem may be better shown 

 by so dividing the discussion. 



a. Interrelationship of hosts. — Gregarious insects. — Very little is 

 known of the parasitism in the Gryllotalpidse and Scutellaridse, but 



