NOTES ON MELANOPHORA RORALIS 
(LINN.) (DIPTERA) 
By Frank Morton Jones 
Wilmington, Delaware 
In 1903 Professor C. T. Brues published (Entomological 
News, vol. 14, p. 291) an interesting account of liis dis- 
covery, made at Woods Hole, Massachusetts, that the 
larva of the Dexid flv, Melanophora r oralis (Linn.), is an 
internal parasite of “sow-bugs” (Oniscidae, Porcellio 
sp.), pupating within the body-cavity of its deceased 
host. 
Meager European. references had indicated the possi- 
bility of a wider range of larval habits for this insect; 
but in 1934 the careful work of W. R. Thompson (Para- 
sitology, vol. 26, pp. 378-448, pis. 15-22) demonstrated 
that roralis (with related species) occurs regularly as a 
parasite of the Oniscidae, and his taxonomic studies of 
larva, puparium and adult placed roralis on a firm basis 
for future recognition. Of this species his material was 
not abundant, and his few field-records related to Euro- 
pean conditions. 
The following observations on roralis were made at 
Vineyard Haven, Marthas Vineyard Island, Massachu- 
setts, hence only a few miles from the place of Professor 
Brues’ discovery of 1903. In the summer of 1946 I was 
conducting a series of experiments with various chemicals 
to which insect-attractant qualities had been attributed. 
In some of these tests the selected chemical was dropped 
upon a plaster-of-Paris disc substituted for the usual bait- 
receptacle in a Rummel-tvpe trap. On August 28, as I 
uncorked a small vial for rebaiting one of these traps 
with isoamyl salicylate, a small black-winged fly circled 
about the rim of the uncorked vial ; and in the nine days 
terminating on that date, forty-one flies of that same 
species had appeared in the trap thus baited, along with 
only three flies of other species. No comparable response 
to other baits was noted, in the three similar and adjacent 
traps operated through this period. These results seemed 
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