Feb. 2. I920 Life History of Euhiomyia calosomae 493 



field. From adults of C. sycophanta collected in the field in late July, 

 1 91 5, and allowed to hibernate in large cages the following winter, one 

 parasitized female emerged on May 25. On May 26 it was dead, and 

 when dissected contained a puparium. The fly issued June 6, 191 6. 

 Between August 4 and 10, 191 6, eggs were deposited upon two beetles 

 and the latter allowed to hibernate in ground cages. On June 5, 1917, 

 the two beetles were found dead on the surface of the earth from which 

 they had recently emerged. Each contained one puparium. One fly 

 issued from these on June 9, 1917. The flies mentioned above were of 

 the winter generation, or parent stock of the summer generation or 

 generations. The first issuance of the summer generation from para- 

 sitized adults of C. sycophanta from field collections was on July 6, 19 15, 

 July 10, 1916, and July 11, 1917. The corresponding last dates of 

 issuance for these years were August 21 for 191 5, July 28 for 191 6, 

 August 3 for 1 917, and as late as August 21 in a reproduction experi- 

 ment in 1 91 7. These dates differed both because of variation in the 

 number of parasitized beetles collected each year and because of varia- 

 tion in the seasons. 



Three female specimens of Calosoma sycophanta were parasitized in a 

 breeding cage late on July 26 or early on July 27, 1917, and were trans- 

 ferred to jars of earth for hibernation. The first female soon entered 

 the earth, making its cavity 5 inches below the surface. The other two 

 females remained active on the surface of earth in the jar and fed for 

 about a week. On August 4 the first beetle was removed from its cavity, 

 killed, dissected, and found to contain two second-stage or dormant 

 hibernating maggots. The second and third females were found dead 

 on the surface of the earth in the jar on August 4 and 7, respectively. 

 These latter beetles contained active third-stage maggots from which 

 eight flies issued between August 15 and 21. Similar records were se- 

 cured in 1 91 8. Most of the flies issuing in the field after July 20 to 25 

 probably perish for lack of a suitable host in a species of Calosoma, since 

 practically all the adults of the latter have entered the earth for hiberna- 

 tion by this time. Presumably the first issuing flies of the summer gen- 

 eration oviposit upon beetles, from which, if they remain active for a 

 sufficient period, there later issue flies of the second summer generation. 



Table II shows the daily issuance of flies for three seasons. It will be 

 observed that the maximum issuance of flies during average seasons 

 occurred between July 6 and August i . Adults of Calosoma sycophanta 

 are most abundant in the field from June 15 to July 10, decreasing in 

 abundance very rapidly after the latter date. Active beetles are very 

 rarely met in the field after August i , hence the late issuing flies find 

 a great scarcity of hosts upon which to oviposit. This in turn accounts 

 for the low percentage of parasitism generally found among the beetles 

 emerging from hibernation in late May and June. 



