1933 ] 
Mermis Parasitism in Ants 
31 
tinctly notched in the middle, so that it is very similar to 
the petiole of the female. Gaster very large and swollen, 
even larger than in the virgin female, with the dorsal scle- 
rites more or less separated, revealing the coils of one or 
more Nematodes through the tense intersegmental mem- 
brane. Legs longer than in the maxima, median and hind 
femora more slender. Sculpture, pilosity and color as in 
the maxima but the sides of the pro- and mesonotum with 
some coarse elongate grooves which are found neither in 
any of the normal worker forms nor in the female. Similar 
but finer, parallel grooves occur on, the dorsal sclerites of 
the three first gastric segments. Traces of these grooves 
occur, however, on the first gastric segment of some maxi- 
mse and on the first and second segments of the female. 
The thirteen known mermithergates, representing five 
species of Camponotus, namely the three above described, 
C. (Tansemyrmex) punctulatus Mayr subsp. minutior Forel 
of the Argentine and C. ( T .) pompeius Emery subsp. 
cassius Wheeler of the Congo, are all very similar, if we 
omit the last, which is merely a parasitized worker minima. 
Each of them exhibits a combination of worker maxima, 
worker minima and queen characters in the structure of 
the head, thorax, petiole and appendages, and may be said, 
therefore, to represent a pathological “intercaste” produced 
by Mermis infestation. The queen characters are less pro- 
nounced in the mermithergates of Camponotus than in those 
of Pheidole, which may even possess small ocelli. The late 
Dr. N. A. Cobb showed that the young Nematodes enter 
the body-cavity of the ant-larva. They probably undergo 
little growth or development till the larva is well advanced, 
but the disturbance they set up in the prepupal and pupal 
development of the host suffices to bring about a consider- 
able diminution in the size of the head and thorax and a 
simultaneous greater differentiation of the latter region in 
the imaginal ant. The series of nine mermithergates of 
C. consobrinus probably arose from a series of larvae that 
were, when attacked by the Mermis, at various points on the 
road to development as normal media and maxima workers 
or had even begun to develop as queens. 
