53 
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the greatest importance when we reflect that the larvae must forage, and 
apparently blindly, through the soil in search of grubs which may be 
.few and far between. The Asilidae are also more or less beneficial in 
the adult stage as predaceous on other insects, though not attacking 
May-beetles since the former are diurnal and the latter nocturnal in 
habit of flight. On the other hand, the adult Tabanidae, or horse-flies, 
are well-known stock pests. The various nematodes and the protozoan, 
bacterial, and fungous diseases of Phyllophaga are but little understood. 
None of these agencies are known to be consistent checks on the multi- 
plication of white-grubs, but occasionally one or the other of them 
appears in such force as to wipe out the entire white-grub population 
in some areas. Favorable climatic conditions and abundance of the 
grubs are the two most important factors promoting the appearance of 
the diseases; and, unfortunately, these conditions can not be duplicated 
in the field by artificial means, and they occur too rarely to act as reliable 
checks. The fungous diseases also affect the insect parasites of white- 
grubs. 
The various native mammals and birds are among our most depend- 
able friends, especially such animals as the skunk and such birds as the 
crows and robins, which seem instinctively to scent the grubs and 
May-beetles and search the soil for them. Many of the other animal 
predators, especially birds, are dependent on the plow to turn up the 
grubs. 
Undoubtedly the increase in white-grubs in certain sections of the 
country is due largely, if not wholly, to the destruction of the wild 
mammals and birds which in years past prevented such insects from in- 
creasing to abnormal abundance. 
Respecting the insect parasites of the adult May-beetles, it should 
be noted that all excepting the sarcophagids, most of which are probably 
not true parasites, are nocturnal in habit as is their host. Most May-, 
beetle species are entirely nocturnal, feeding on the foliage of trees at 
night and hiding beneath rubbish or in the soil by day. The tachinid 
parasites of the adult deposit their eggs on the beetles while the latter 
are quietly feeding or copulating and are least likely to be disturbed; 
but the ortalid flies of the genus Pyrgota attack the beetles in flight. The 
Pyrgota species deposit their eggs in the bodies of the May-beetles, the 
opening of whose elytra in flight exposes the only part of the body soft 
enough to be pierced by the ovipositor of the parasite. A few sarcopha- 
gids may be regarded with reasonable certainty as May-beetle parasites, 
and it is interesting to note that they have been reared only from P. 
lanceolata and P. cribrosa, which are day-flying species, as are these 
parasites. 
When we further reflect that these enemies are likewise attacked by 
parasites, that some birds and mammals which destroy Phyllophaga 
may also destroy the beneficial parasites, that the adult of one predaceous 
larva may prey on the adult of a similar predaceous larva, and that the 
oe 
