R. W. Glaser and A. M. Wilcox.
On the Occurrence of a Mermis Epidemic Amongst Grasshoppers.
Psyche 25:12-14, 1918.

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1.2 Psyche [February
In all figures only a portion of the terga (which are symmetrical) has been shown, since the missing portions are exactly like those figured.
Fig. 1. Terga and wing bases of a Plecopteron. Fig. 2. Terga and wing bases of the Coleopteron Photuris. Fig. 3. Terga and wing bases of Ernbia major. Fig. 4. Terga and wing bases of the Dermapteron Echino8oma. ON THE OCCURRENCE OF A MERMIS EPIDEMIC
AMONGST GRASSH0PPERS.l
BY R.'W. GLASER and A. M. WILCOX.
While engaged in some investigations on grasshoppersy near Dummerston Station, southern Vermont, this past summer (1917), our attention was attracted to a high mortality amongst these insects (Melanoplus atlanis and M. bivittatus) . The two species,. especially M. atlunis, are extremely bad pests in this region of the countryy attacking corn? wheat? oats and clover to such an extent that during certain summers the farmers become nearly frantic. Therefore? the high mortality amongst the grasshoppers, which appeared during the latter part of Auwst and the early part of September? was exceedingly gratifying.
We soon discovered that this mortality was due to a species of Nematode belonging? as we supposed at the time, probably to the family Mermithid~. Subsequently (Sept. 20, 25 and Oct. 61, we sent large shipments of these worms to Dr. N. A. Cobby of Wash- ington? D. C., for identification, Dr. Cobb was able to give us only a provisional identification on account of the utter absence of males in all of our shipments. . We made collections of parasitized grasshoppers from a large variety of fields and as stated, sent a large number of specimensy but curiously enough no males were found. Dr. Cobb in a letter said: "Nothing I have learned would preclude your specimens from belonging to the same species as that referred to by hidy under the name of Mermis ferruginea, which 1 Contribution from the EntomologicaI Laboratory of the Bussey Institution in eo6peration with the U. S. Bureau of Entomology.
Bussey Institution: No. 146.




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PSYCHE, 1918.
VOL. XXV, PLATE I.
Fig. 1
3 Fig. 3
CRAMPTON-T~X'~~ and wing Bases.




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19181 Gluser and Wilcox-A Mermis Epidemic amongst Grasshoppers 13 he says was common in Locuda carolina near Philadelphia; but
there can be no certainty about the matter until males of the pres- ent species are obtained and a comparison made with Leidy's material, which may or may not be in existence.'' Dr. Cobb
further stated that after the nematodes leave the grasshoppers, they make their way into the soil and that their further history is obscure.
In Vermont the nematodes parasitized both M. ailanis and M. bivittatus. The worms seem to leave the bodies of the grasshoppers when these insects are maturing.
We had not the opportunity
to observe grasshoppers in the early stages of parasitism, but in August and September dissection of a large number of the insects showed that the worms were located within the body cavity. Later in the season, when the worms are about to emerge, the grasshoppers fall over on one side, kick for a time and then die. In the meantime, the worms gradually bore their way through the body wall and reach the exterior after which they make their way slowly into the earth. Usually only one worm parasitizes a grasshopper, but by dissection we have often found two or three and in one case we found forty. Needless to say, that when an insect contains so many worms the abdomen is considerably swollen.
The length of these female worms varied from two to eight inches. It is extraordinary that with hundreds of hoppers dying everywhere, we were unable to find any males. A great many nematodes, at one stage of their life cycle, seek water on leaving their hosts and there mature, or wait until another host presents himself. We placed about two dozen of our worms in a bowl of water in which they seemed to flourish for about two weeks. However, the localities where the hoppers, and conse- ,quently the worms abounded were free from streams, ponds or marshes of any kind. The Connecticut River flows through a val- ley at a distance of about one-half mile so it seemed unlikely that the worms would travel so far. In all probability, we thought, the worms make their way into the soil on leaving the insects and this we found true. We placed recently dead parasitized hoppers in boxes containing earth. In about three days the boxes were ex- amined and the worms were found coiled up at a depth of about one foot. Often a number would be coiled up together in one



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14 Psyche [February
spot. An examination of the soil in the fields revealed quantities. of the worms below the surface at a distance of six inches to one foot. November the 7th and 8th, long after the grasshopper sea- son, the ground now cold was again broken and the nematodes wereafound coiled up at about the same distance below the surface. Undoubtedly they hibernate in these positions. During the highest mortality we made a series of dissections in order to determine the per cent. of parasitism. On a place called the Halladay Farm, we obtained the following astonishing high figures by the dissection of M. bivittatus. Sept. 8. 100 Q Q dissected and worms found in 59y0. " 10. 80Q Q
< 6 66 6 6
" '' 76y0.
" 12. 50 Q Q "
6 6 6 6
" " 62y0.
" 8. 4033.
66 66 CC
" " 12y0.
" 10. 6038
66 66 6 6
'< '< 21y0.
" 12. 100d 8 "
& c $6
6' '< 12y0.
On a place called the Tarbox Farm, we dissected about equal! numbers of M. bivittatus and M. atlanis and obtained the following:. Sept. 8. 100.9 Q dissected and worms found in 22y0. " 10. 75 Q Q "
6 6 6 6
" " 2570.
" 12. 60 Q Q
66 & 6 66
'' " 25y0.
" 8. 9083 "
66 66
'' " 370.
'' 10. 8033 "
66 66
" " 5y0.
" 12. 1003 3 "
66 66
" " 2%.
In both series of dissections it will be noticed that the percentage of parasitism in females is much higher than in males. Since the
life-history of the worm is still so obscure we are at present unable to offer any explanation for this fact.
How the grasshoppers become infected is unknown. Since the
nematodes are so large when they leave the grasshoppers in order to burrow into the soil, we are under the impression that grass- hoppers are the secondary hosts. It is difficult to imagine what animal might constitute the primary host. Perhaps some other insect may furnish the clue to this interesting question. Next summer we hope to extend our observations and attempt to gain a more complete insight into the life-history of this Merrnis* parasite. Some parasites fluctuate so numerically from one season



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