REVISION MALACOSOMA HUBNER IN NORTH AMERICA 29 



temperature is not known, but the maximum temperature recorded 

 in the U.S. Weather Bureau's Climatological Data for 18 April 1962 

 for nearby localities was 84° F. at Burnet (10 miles east), 90° F. at 

 Llano (20 miles west), and 86° F. at Lampassas (25 miles northeast). 



Sullivan and Wellington (1953) found that last instar disstria larvae 

 became overheated and photonegative at an air temperature of 34.5° 

 C. to 35.5° C. (approximately 95° F.) under laboratory conditions. 

 They also reported mean internal temperatures of 35.4° C. for mature, 

 photonegative disstria larvae engaged in prepupational travel in the 

 field. The air temperatures at Inks Lake State Park on 18 April 1962 

 probably did not reach 95° F., but the day was bright and clear, so 

 larvae exposed to the sun could have been overheated. Since the 

 disstria larvae were found resting in the shade, it is reasonable to 

 assume that they were there because they had become overheated. 



From these observations it seems evident that tigris larvae are able 

 to tolerate warmer body temperatures than disstria larvae, or else they 

 are somehow able to maintain a lower body temperature than disstria 

 under similar conditions of exposure to the sun. It is possible that 

 tigris larvae have a reinforced photopositive reaction similar to that 

 reported for M. americanum and M. [californicum] pluviale by Sullivan 

 and Wellington, but this seems unlikely since their habits are much 

 more similar to disstria's in every respect. 



Of what use is the tent, and is there any advantage in building a 

 large tent, or in building no tent at all? 



One use that all species make of their "tents," whether they be just 

 a mat of silk, or large and spacious, is as a base for attachment when 

 molting. They hook their crochets into the silk, and apparently are 

 more securely anchored than they would be if they did not have the 

 silk. Most individuals of a given colony molt at the same time. The 

 bunches of exuviae which are left behind are often more conspicuous 

 than the larvae, and have sometimes been mistaken for dead larvae. 

 The tentbuilders usually retire inside their tents to molt where they 

 appear to be better protected than their nontentbuilding relatives. 

 Nevertheless, the nontentbuilders do very well, so any protection 

 afforded by a tent during molting is not essential to all species, although 

 it may be important to those which build large tents. This remains 

 to be determined. 



Certainly, those species which build conspicuous tents are at a defi- 

 nite disadvantage as far as predation by man is concerned, since hu- 

 mans notice the "ugly nests" and go out of their way to destroy them, 

 while the nontentbuilders go unnoticed unless they are very abundant. 



The argviment can go both ways as far as other parasites and preda- 

 tors are concerned. Potential enemies may be attracted by the tent, 



