The Puss Caterpillar. 



13 



was directly responsible for the death of all the specimens under 

 observation. It seemed to spread more rapidly when they were 

 kept in close association, but also attacked them readily when they 

 were scattered on the limbs of a tree. 



Since 1913, when the severe stings inflicted on man by this pest 

 came to the writer's attention, there has been a very noticeable 

 variation in its abundance from year to year. It was very abundant 

 in San Antonio in 1913 and 1914, apparently decreased during the 

 next two years, and waves of unusual abundance have occurred 

 since. At Dallas the caterpillars were fairly numerous in. 1914, but 

 less so for several years follow- 

 ing. There was an imprece- 

 dented outbreak of them dm'- 

 ing 1920 in both Dallas and 

 Fort Worth, and a very marked 

 decrease in their niunber during 

 1921. This periodicity is no 

 doubt rather closely correlated 

 with the effectiveness of the 

 natural control agencies. 



In addition to the bacterial 

 disease, and probably of even 



greater importance, are 



the 



tachinid parasites Exoristajia- 

 virostris v. d. W. (Fig. 11) and 

 Phorocera daripennis Macq. 

 (Fig. 12). The waiter is in- 

 debted to Dr. J. M. Aldrich and 

 H. J. Reinhard for the deter- 

 mination of the many lots of 

 these flies submitted to them. 

 At San Antonio, Tex., in 1914, 

 E. jiavirostris was most abund- 

 ant. As many as eight flies 

 emerged from a single cocoon, 

 and fully 75 per cent of the larvae 

 of the fall generation were para- 

 sitized by the two species. At 

 Dallas, P. claripennis appears to 

 predominate. Only a single 

 specimen of this fly develops in 

 a cocoon. Emergence usually 

 begins earlier in spring than 

 with the other species. 



Both of these species have been observed to overwinter in the larva 

 stage in the host within the cocoon. These flies usually emerged in 

 March and April from cocoons spun in October and November, but 

 some came out in the fall. The shortest period observed from spin- 

 ning of the cocoon by the host to emergence of the flies was 11 days 

 in summer and 22 days in fall. Two specimens of E. Jiavirostris 

 were observed to leave the caterpillar and pupate August 22, and the 

 adults emerged September 8. 



Fig. 10.- 



-Leaf showing skeletonizing due to the feeding 

 of young puss caterpillars. 



