NOTES ON A SPECIES OF BARNACEE (DICH ELASPIS) PARASITIC ON THE 
GILLS OE EDIBLE CRABS. 
By ROBERT E. COKER. 
Iii the summer of 1900 Prof. H. V. Wilson, at that time director of the Beaufort 
Laboratory, suggested that, in view of the economic importance of the edible crabs, 
a fuller knowledge of the life histories of the ectoparasites of these forms was 
desirable. The following notes on one of the most interesting of such parasites 
are the outcome of an investigation carried on during parts of that and the following 
summer. 
It is a pleasure to express my thanks to Professor Wilson for many helpful 
OCCURRENCE AND HABIT OF ADULT. 
A large number of the common edible crabs, or blue crabs ( Callinectes sapidus 
[Ordway] Rathbun), of Beaufort, N. C., are found to be infested with a small lepadide 
barnacle, ectoparasitic on the gills (tig. 1). This form was first observed at Beaufort 
by Mr. T. G. Pearson. To ascertain somewhat definitely the proportion of crabs 
containing this parasite, record was made of 180 mature crabs examined during 
August and the first half of September, and barnacles were found in 128, or in 71 per 
cent. These crabs were taken just as they were brought into the laboratory, no 
selection being made except that soft crabs and evidently young - crabs were disre- 
garded. The barnacles were much more abundant later than earlier in the summer. 
The sexes were found to be unequally burdened; the percentage for males 
infested was only 56, while for females it reached 89 per cent. It was also easily seen 
that the average number of barnacles in infested females was considerably above the 
corresponding average for males. A possible explanation of this difference is that 
F. C. B. 1901—26 
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