Mar. 17, 1923 
Agamermis decaudata a Nema Parasite 
923 
A review of the information obtained from the returned questionnaires 
also emphasizes the economic value of Mermithids, a fact surmised earlier 
by a number of entomologists but never proved in a substantial way. Of 
130 returned questionnaires, 53.6 per cent state that Orthoptera were the 
hosts. In 51 cases the writers made observations regarding the effect of 
the parasite, mostly on an individual host. Of these latter observers, 
85 per cent report an injurious effect on the host, 71 per cent stating that 
the normal development of the host was prevented, 47 per cent stating 
the fecundity of the host was reduced, and 53 per cent that the host was 
killed. Most of these statements seem mainly the result of fortuitous 
observation on a limited scale; in general, they corroborate those already 
mentioned in the literature. Hagmeier (3) estimated that on a meadow 
33 per cent of all grasshoppers were infested with Mermis; Glaser and 
Wilcox (2) in this country estimated infestation up to 60 per cent; 
Leidy (4), very frequent; Steiner’s observations (<?, p. 223) showed in a 
garden heavily infested with the snail Limax agreslis, 20 to 30 per cent of 
them mermithized. 
EXPERIMENTS AT THE EASTERN FIELD STATION OF THE BUREAU 
OF ENTOMOLOGY AT FALLS CHURCH, VA. 
During the early part of July, 1922, it was noticed that grasshoppers 
in the vicinity of Falls Church, Va., were infested by a Mermithid para¬ 
site. From that time until cold weather, collections were made over an 
area of several square miles, and a total of 3,332 grasshoppers was 
examined. Of the 824 Tittigonidae included in this number, very nearly 
all were Orchelimum vulgare Harris. Of the remaining 2,508 Acrididae, 
about 90 per cent were Melanoplus femur-rubrum Deg. Mermithid 
infestation was found to average 12 per cent, increasing to about 25 per 
cent in heavily infested regions. 
Records based on the examination of 2,498 grasshoppers, the sexes of 
which were determined before dissection, show the males and females 
to be about equally parasitized. 
As the nemas do not reach sexual maturity in the host, but moult 
once in the soil after leaving the host, the determination of the material 
taken from grasshoppers is a difficult task. However, it is certain that 
the greater number of the nemas were varieties or races of Agamermis 
decaudata , with an occasional species of another kind. 
The parasites begin to leave the hosts by the latter part of August, if 
not before, and are nearly all out by the first of October. Their method 
of exit is by forcing their way through the body wall of the insect. In 
one carefully observed case the parasite issued from the side of the abdo¬ 
men, head foremost, and was free in a very few minutes. The parasite 
was assisted by the kicking of the grasshopper, whose feet became 
entangled in the coils of the nema. 
Once free from the host, the Mermithids make their way into the soil 
to a depth of 3 to 20 cm. The females go down from 4 to 8 cm., seldom 
deeper. Here they coil up in the “nest,” forming a “knot,” and ap¬ 
parently never again move about. The males move through the soil 
more freely, as it is evidently their function to seek out the females. 
The “knots” as dug from the soil during the winter contain one female, 
rarely more, and from one to seven males. 
In order to determine the approximate Mermithid population in an in¬ 
fested region, 16 square feet of soil were examined to a depth of 30 cm. 
(12 in.). The yield was 132 Mermithids, or at the rate of 359,370 per acre. 
