use of chelae by green crabs, and Borradaile, Potts, 

 Easthani, and Saunders (1958) described the hold- 

 ing, severing, and chewing action of the green 

 crab's niouthparts. 



Cai'thy (1958) discussed accessory sense organs 

 other than eyes which may help to direct green 

 crabs to food. I observed how the chemical senses 

 arouse green crabs in the laboratory. Ten crabs, 

 from which the eye stalks had been removed, were 

 held in an aquarium where 54 Mya lived in the 

 sand. During 18 days of observation, all the crabs 

 remained buried in the sand and did not search for 

 the clams. On the 18t.h day, when juice of the 

 quahog {Mercenaria meyxenaria) was poured into 

 the aquarium, the crabs almost immediately rose 

 out of the sand and moved about, as if in search 

 of food. Such an imoriented reflex action of the 

 whole animal or kinesis to chemical stimuli was 

 discussed by Allee, Emerson, Park, Park, and 

 Schmidt (1949). 



Abundance of certain foods undoubtedly affects 

 predation by green crabs and is interrelated with 

 their food-getting capabilities. Bottom samples 

 taken in 1954 by Smith (1955) from areas pro- 

 tected from crabs by Saran screening had more 

 Mya per square foot at Hales Cove than at Hamp- 

 ton Harbor. During the saine year, more crabs con- 

 tained Mya at Hales Cove than at Hampton 

 Harbor. Thus, the crabs at Hales Cove reacted to 

 the greater relative abundance of Mya by eating 

 more of them. 



Small animals were most numerous in the 

 stomachs. Many crabs consumed large numbei's 

 of such small mollusks as Gemma and Hydrobia 

 (table 4). Some pelecypods were ingested soon 

 after setting, when they were very small. Smith 

 (1955) observed that clams 2 to 12 mm. long 

 were most abundant at Hales Cove in September 

 and October and deduced that this phenomenon 

 was probably an annual event. Mya occurred most 

 frequently in green crab stomachs during Sep- 

 tember to November. 



Some foods were eaten frequently by certain 

 groups of crabs. S-partina was found most often in 

 intertidal crabs (fig. 4), although crabs from both 

 the intertidal and subtidal zones usually contained 

 more animals than plants. Plant foods, especially 

 Spartina, were abundant near the caves inhabited 

 by green crabs and on islands that were relatively 



' M = male; F = female. 



2 The stomach of the crab also contained one Nereis. 



ngar the subtidal zone. Subtidal crabs contained 

 animal foods, apparently from the clam flats, 

 rather than Spartina. 



THE INFLUENCE OF CRAB SIZE 

 ON FEEDING HABITS 



I analyzed the relation of crab size to stomach 

 contents because food habits sometimes change as 

 an animal grows. The stomach contents differed 

 between crabs less than 30 mm. wide and those 

 30 mm. wide and larger (fig. 5). The groups are 

 designated as small and large in the text to 

 simplify presentation. The original data on food 

 occurrence are separated by size intervals of 10 mm. 



In general, all sizes ingested the same kinds of 

 foods and differences in food were minor. The 

 smallest crabs were perhaps exceptions because 

 fewer different kinds of food were eaten. 



Plants and soft-shelled animals were most fre- 

 quent in the stomachs of small crabs. More small 

 than large crabs contained Spartina, but the fre- 

 quency of algae was nearly equal in crabs from 

 the two size groups. Small crabs also ate animals, 

 but only small arthropods and insects were more 

 common in small than in large crabs. Numerous 

 stomachs of small crabs contained small, chitinous 

 fragments, probably from small arthropods. 



Large crabs contained hard-shelled foods, such 

 as mollusks, more often than did small crabs. Large 

 crabs concentrated on the clam flats when feeding. 



FEEDING HABITS OF GREEN CRAB 



189 



