924 
Journal of Agricultural Research 
Vol. XXIII, No. II 
Eggs are laid in large numbers until both the nemas and the wall of 
the nest become plastered with them. Egg counts show that each fe¬ 
male lays, on an average, at least 5,000 eggs. Under the 16 square feet 
referred to in the preceding paragraph, 32 “knots’' were surrounded with 
eggs. If the average number of eggs per nest is 5,000 (probably a very 
conservative figure) there will be, provided all the eggs hatch, 435,600,000 
larvae per acre. Each foot will therefore support a population of 10,000, 
and each square inch of surface will have below it about 70 of these 
young Mermithids 
The egg has the shape of a slightly flattened sphere, and measures 119 
by 105 microns. The rate of its development is influenced by external 
conditions, particularly temperature. At the end of five or six days, 
with average September weather, the embryo takes the form of a single, 
circular coil, almost filling the shell. At this point in its development 
there is a rapid proliferation of cells at the posterior extremity, the ends 
of the loop overlap and in a short time several coils are developed. As 
the length of the embryo increases new coils are formed until, at the end. 
of about a month, the young larva reaches its full length of a dozen or 
more coils—that is, 3 to 4 mm. The development of eggs deposited late 
in the fall seems to be retarded by cold weather, for material collected in 
March still contains the earlier stages of development. The hatching of 
the eggs is probably brought about by the warm spring weather, as eggs 
brought into the laboratory in winter and kept at room temperature 
hatch freely after three or four days. 
After hatching, the larvae work their way to the surface of the soil 
and enter the newly hatched grasshopper nymphs. 
Artificially infested grasshoppers containing six or eight Mermithids 
die in about eight days. In fact it may be doubtful if grasshoppers 
harboring more than one parasite ever reach maturity. The ovaries 
of infested females which do survive are vestigial, never producing 
functional eggs, and it is likely that the males are also rendered sterile. 
The exit of the nemas, sometimes at least, results in the death of the 
grasshopper, and there is every reason to believe that this is always 
the case. 
STRUCTURE AND BEHAVIOR OF THE FREE-LIVING LARVA 
The rear five-sixths of the decaudata larva has a certain uniformity of 
structure. Here the cuticle and body wall are typically nemic. The 
body cavity is filled by a moniliform series of elements, having somewhat 
the general character of nemic intestinal cells, but there is no lumen and 
no trace of an anus. Each of these 50 to 70 cells (trophocytes), in addition 
to its nucleus, protoplasmic network, and minute proteid granules, is packed 
with spherical 3-4 micron fat globules, melting at about 55 0 C., and 
contains a thin-walled catabolic vesicle holding a birefringent crystal. 
As the larva ages, the fat disappears, while the vesicle increases, thus 
pushing all other contents of the cell to one end. In a few weeks no 
fat remains, and the nema has a segmented aspect. By expending the 
fat of the trophocytes, the posterior five-sixths of the nema becomes the 
active mechanism for driving the strongly cephalated anterior sixth to, 
and into, the host. 
On entering the host the driving mechanism is shed at a predetermined, 
elaborately prepared node, and only the cephalic portion becomes par¬ 
asitic. The node at which this automatic amputation takes place is 
prominent in the free-living larva. Persisting as a little altered terminal 
scar, it indicates that no moult occurs during the parasitic life. Usually 
