384 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



the maggot died while still very small. The ventral surface of the 

 thorax appears to be a safer and more protected position for the deposi- 

 tion of the egg. 



Incubation of the egg and the growth of the maggot while small takes 

 several weeks, but the growth of the maggot from one-third to fully 

 grown takes only two or three days. The grub seems not at all dis- 

 commoded by the presence of the parasitic maggot while it is small, 

 but when the maggot becomes about one third grown, the grub is less 

 active, its movements being confined to a restricted area. Its feeble 

 movements in the earth appear to have the effect of preparing a cell 

 • which is well adapted for the spinning of the cocoon of the parasitic 

 larva. In practically all cases, all of the softer portions of the grub 

 are absorbed by the parasite, and only the heavily chitinized head and 

 legs and the shriveled skin of the grub are left. 



In the earthen cell, which is practically empty after the destruction 

 of the grub, the Tiphia larva spins its cocoon. This is an elongate 

 pear-shaped affair, or it may be described more exactly as shaped like 

 an Indian club or a summer squash with the neck eliminated. Indeed, 

 comparison of its shape to that of a squash is more nearly correct, as 

 the pointed tapering end is noticeably bent to one side. The cocoon 

 is composed of downy silk of uniform texture, somewhat the color of 

 khaki cloth. Often the color is darker or redder, but the variation 

 is trifling. The silk of the smaller species of Tiphia is light yellow or 

 flaxen in color. The color bleaches quickly in bright sunlight, and 

 cocoons found in fields that have been plowed only one or two days 

 previous show the side exposed to the sun faded to a light gray. The 

 cocoon is loosely suspended in the cell by scattered strands of silk, 

 but from the pointed end it is more firmly supported horizontally by a 

 little button of silk in the outer layer of the cocoon. This little button 

 is firmly attached to the side wall of the cell. Although the cocoon 

 appears soft and downy, it is really quite firm underneath the loose 

 outer network of silk, and the inner cocoon, while composed of silk of 

 the same color, is very tightly woven. Entangled in the loose outer 

 threads of the cocoon, the mandibles, skull (head case) and shriveled 

 skin of the grub are usually to be found. 



It has been supposed that the eggs are often deposited on grubs too 

 small to furnish sufficient nourishment for the parasite maggot to 

 become fully grown and in such cases small cocoons are formed. It 

 is almost certain, however, that these smaller, flaxen colored cocoons 

 are produced by another smaller species of Tiphia, which attacks only 

 small grubs, as these small flabby cocoons are often found in fields 

 where large grubs are abundant. The males of Tiphia are considerably 

 smaller than the females and the cocoons from which they emerge 

 are usually smaller than those of the females. 



