1948] 
Jones — Melanophora roralis 
33 
while, twenty-five apparently healthy adult sowbugs had 
been installed in a gallon jar, with layers of bark for 
shelter and concealment, and pieces of apple and of po- 
tato for food. On August 10 this jar was found to con- 
tain 18 living sowbugs, fragments of 7 others, and 3 living 
puparia of roralis; on August 21, only 13 living sowbugs 
remained, and no additional roralis. That is, at least 
12% parasitism was indicated and a much larger fatality 
through cannibalism, a recognized sowbug trait. Exami- 
nation of the 13 survivors showed that among these, two 
species were represented — Oniscus asellus Linn, and Por- 
cellio scaber Latr. ; and the fragments enclosing roralis 
puparia indicated that both these species had served as 
hosts. Emergences of roralis adults (four) took place on 
August 11 and August 15. 
Adult roralis is diurnal in habit, rarely appearing 
among the overnight captures of the bait-traps, and only 
once in a light-trap operated throughout the season. 
Further experiments with chemical baits (conducted in 
collaboration with Mr. Charles P. Kimball of Rochester, 
New York) forced some modification of the belief that 
isoamyl salicylate possesses a unique attraction for 
roralis , for in 1947 traps baited with other chemicals 
sometimes captured fully as many flies of this species, and 
it became a question whether the entrance of the flies into 
the traps, in part at least, might not be ascribed to their 
habit of penetrating and exploring narrow crevices and 
cavities, rather than a response to attractive odors. A 
few experiments with an unbaited trap tended to con- 
firm that suspicion. 
The almost uncanny ability of roralis to gain entrance 
to screened houses may be attributed to this habit. In- 
doors, these flies do not usually evince strong attraction 
toward food, and their lives are apparently short, for 
their dead bodies occur commonly on window-sills, in 
cobwebs, and not rarely in bathtubs or in bowls of wash- 
stands where perhaps the presence of moisture attracts 
them. 
Long ago it was suggested (W. D. Pierce, 1907, U. S. 
Bull. Ent. 64, pp. 15 and 22) that sowbugs, because of their 
