628 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Famities SCOLIIDAE AND TIPHIIDAE 
The Scoliidae and Tiphiidae families contain closely related wasps, 
many of which are parasitic on the larvae of white grubs (Scara- 
beidae). They are medium- to large-sized, hairy insects, prevailingly 
black, often spotted or banded with yellow or red, and their wings are 
frequently fuscous. 
Tiphia inornata Say is one of the commonest and most important 
parasites of the grubs of the genus Phyllophaga in the United States. 
Wolcott (435) studied the life history of this species in Illinois, and 
reported that under favorable circumstances 7iphia greatly reduced 
the numbers of grubs and in some cases practically exterminated 
Phyllophaga from limited areas. Since white grubs often cause seri- 
ous losses in nurseries, and the adults feed heavily on many forest 
trees, the parasite is of considerable economic importance to our 
forests. The adult is from 14 to % inch long, shiny black, with 
grayish hairs on head, thorax, and abdomen. The wings are short 
and fuscous. The female seeks out grub larvae in the soil and has 
little difficulty in working her way through black, heavy clay soil in 
good tilth and seems to be successful in finding grubs, even where they 
are not abundant. The wasp stings the grub until it ceases to resist 
her attempts to deposit an egg on it, but the effect of the sting is only 
temporary. In fact, the egg or the young maggot is often brushed off 
by the grub as it burrows through the soil. 
The ventral surface of the thorax appears to be the preferred and 
safest position for egg deposition. Incubation of the egg and growth 
of the maggot, which feeds externally, requires several weeks. At 
first the grub does not seem to be affected, but when the parasite 
becomes about one-third grown its movements are restricted and it 
prepares a sort of cell in which the parasite larva spins a tough silken 
cocoon beneath a loose outer network of silk. The winter is spent 
within the cocoon, and the adult emerges about the middle of May. 
A number of factors limit the abundance of 7iphia. The females are 
not strong fliers, and they tend to remain in the field where the imma- 
ture stages were passed. | 
White grubs are usually abundant in fields where there are trees 
on which the adult beetles feed, but in some localities only a single 
generation of the dominant species of Phyllophaga may be present, 
and most species of Phyllophaga require 3 years for the completion 
of their life cycle. In the year that full-grown grubs are abundant 
there is an ample supply of hosts, but the next year only beetles, eggs, 
and very small grubs are present. Therefore, in certain years 7iphia 
finds no suitable host material and must disperse to new territory, 
unless large numbers are to perish without depositing eggs. Other 
factors affecting 77phia abundance are parasites, fungi, and unsuitable 
soil conditions, but when soil conditions are unsuitable for 77phia, 
another parasite, the scoliid wasp Myzine quinquecincta (F.) is fre- 
quently abundant. 
Famity BETHYLIDAE 
The Bethylidae are a large family of parasitic wasps widely dis- 
tributed throughout the world. Our species are of small or moderate 
size. ‘Those of known habits prey upon either coleopterous or lepi- 
