102 BULLETIN 15 7, IT. S. NATION" AL MUSEUM 



When about to molt for the last time the caterpillars usually crawl 

 to the top of the highest available dead cattail or other herbaceous 

 plant, where they often gather in considerable numbers. After the 

 molt they scatter, and they then appear to be much less abundant, 

 for at any given time most of them will be feeding or will be on or 

 near the ground searching for the food plant. 



In the chief locality for this insect at Cabin John it was very 

 abundant in 1926. But in that year the main patch of turtlehead 

 was mowed down during the summer. In the following spring, when 

 I visited the locality in company with Dr. Karl Jordan, there was no 

 trace of the insect where previously it had been abundant, though a 

 few of the caterpillars were found on some small groups of turtle- 

 head some distance away. In 1927 extensive and continued search 

 of the whole area, on one day in company with Irvin N. Hoffman, 

 failed to reveal any trace of caterpillars or of adults, and neither 

 caterpillars nor adults were to be found in 1929. In 1930, however, 

 the caterpillars reappeared in numbers on the main patch of turtle- 

 head, though they were not found on the small groups or on the 

 scattered plants. 



As the search of this area in 1928 and 1929 had been very thorough, 

 it is probable that the insect had been reintroduced in the summer of 

 1929 and had not simply escaped detection in the two seasons in 

 which it was not found. This explanation of its reappearance 

 receives added weight from the fact that in 1930 only a single cater- 

 pillar parasitized by Apanteles ewphyclryadis was found, whereas the 

 normal amount of parasitization by this species here is about 18 per 

 cent. 



Genus BRENTHIS Hubner 



BRENTHIS MYRINA (Cramer) 



Silvered Bog Feitillary ; Myeina 

 Plate 3, Figures 5 to 7; Plate 4, Figure 5 



Occv/rrence. — I have found this butterfly only in the boggy pasture 

 on the south side of the road from the Beltsville, Mel., railroad sta- 

 tion to the experiment farm of the Bureau of Animal Industry, 

 Department of Agriculture, where it is rather common. At the 

 height of the season, in the middle of July, 8 or 10 may be caught 

 in the course of an afternoon. 



Season. — This species first appears in the last days of June or just 

 after the first of July and becomes increasingly common until the 

 middle of July, when worn individuals preponderate, although fresh 

 ones are still to be found. My earliest record is a perfectly fresh 

 specimen taken on June 29, 1929. As the afternoon of June 22 had 

 been spent in carefully searching the bog without result, the insect 



