81 
from 15 to 43 days, apparently depending largely on temperature and 
quite likely also on moisture conditions. Although Phyllophaga grubs 
are more often attacked than others, we have reared this parasite also 
from grubs of Cotalpa lanigera, and it seems not unlikely that it may 
infest other large scarabaeid grubs that occur in cultivated fields. The 
maggot and puparium are distinguished from the related dexiids by the 
posterior spiracles, shown in Figure 15. In no case have we found 
more than two larvae infesting a single grub, the number usually being 
one. to a grub. , 
As has been shown, M. disjuncta has a wide range of distribution 
and in certain areas it undoubtedly has a marked influence on the abun- 
dance of grubs. In a collection of grubs taken at Farmington, Mich., 
June 12, 1916, over 25 per cent. showed disjuncta parasitism. We have 
found it especially abundant in the eastern part of Michigan near Lake 
Huron, which would indicate a preference for, and an ability to live and 
seek its host advantageously in, sandy or sandy loam soils, as might be 
expected from our knowledge of its mode of life. 
MIcROPHTHALMA PRUINOSA Coq. 
Eight Phyllophaga grubs were received at the Lafayette Station 
june 14, 1915, from Framingham, Mass., where they were reported to be 
injuring pine and spruce seedlings. They were placed in individual 
one-ounce tin boxes, and on July 16 one was dead, and in the semi- 
liquid remains the anal ends of two dipterous maggots protruded through 
the body-wall, exactly as had already been observed for the parasite 
Microphthalma disjuncta. By ten o’clock the following morning (July 
17) one of the maggots had formed a puparium, which, however, was 
still uncolored. By 2:30 p. m. the puparium had taken on its natural 
reddish brown color, and between 2:30 and 5:30 p. m. the second mag- 
got pupated. One adult, determined by W. R. Walton as M. pruinosa, 
issued August 27, but the record for the second adult which issued was 
lost. From the 7 remaining grubs + adults were obtained, all being 
Phyllophaga anxia (dubia, form insperata), and as the grubs had been 
carefully examined on receipt and no specific difference found, it is very 
probable that the species destroyed by this parasite was P. anxia. This 
seems to have been the first recorded observation (16) concerning the 
host relations of this tachinid. We have since reared a single specimen 
of this species from a grub collected at Chelsea, Vt., May 31, 1916, by 
Mr. H. E. Smith. In this case the grub died July 7, which was coinci- 
dent with the first appearance of the parasitic maggot, the adult fly 
issuing September 1 of the same year. 
M. pruimosa seems to be widely, though sparsely, distributed, for 
it was described from specimens collected in New Mexico and Mexico, 
and Dr. Aldrich has a specimen which he collected at Brookings, S. 
Dak., in 1891 or 1892. Apparently the species is of little economic im- 
. portance in controlling white-grubs, owing to its scarcity. 
