intact. Because of their frequent occurrence in the 

 stomaclis, the si>ecies Mya avenaria, Geimiui 

 gemma^ and Mytilus edidis were separated in the 

 analyses; otlier species of pelecypods were com- 

 bined. Gastropods were identified from the shells, 

 operculi, and sometimesthe radulae. Annelids were 

 identified by their jaws (whole worms were rarely 

 found). Arthropods could rarely be identified to 

 species but were separated into three general 

 groups: (1) crabs — the hea\'y, pigmented exoskele- 

 tons of green crabs, rock crabs, and horseshoe 

 crabs; (2) small arthropods — ^the light, translu- 

 cent exoskeletons of amphipods, isopods, and small 

 shrimp; and (3) baniacles (shells and bodies). 

 Insects, fish remains (mostly bones), Foramini- 

 fera, and colonial hydroids were also found. Only 

 two plant foods, algae and cordgrass {Sjym'tin-a), 

 were identified. Many stomachs contained food 

 remains that were classified as unidentified tissues. 



THE RELATIVE FREQUENCY OF FOODS 

 IN GREEN CRABS 



Mya was only 1 of ;!1 kinds of food identified in 

 the stomach contents during this study (table 3). 



Table 3. — List of organisms in the stomachs of 3,979 green 

 crabs collected in 19S4-56 



Both animal and plant foods occun-ed in the stom- 

 achs, but not with equal frequency (fig. 3) ; only 

 one-third of the 3,979 stomachs with food con- 

 tained plants, whereas 88 percent contained ani- 

 mals. Mollusks, and especially pelecypods, were the 

 most frequent animal foods in the stomachs, and 

 Mytiliis was the most frequent species. Mya, 

 Gemina. and other pelecyix)ds occurred in about 



one-fourth of the stomachs. Only the plant food 

 Spartina was found in as many stomachs as some 

 of the pelecyix)d species. Remains of large arthro- 

 pods and fish, probable indicatoi-s of cannibalistic 

 and scavenging food habits, respectively, were in 

 few stomachs ; obviously green crabs are essentially 

 omnivorous. 



THE FEEDING CAPABILITIES 

 OF GREEN CRABS 



Certain items in the stomachs and observations 

 of feeding in the laboratory provided informa- 

 tion on the food-gathering capabilities of green 

 crabs. A few stomachs contained the bodies and 

 tlioroughly crushed shells of bai'uacles. The pres- 

 ence of mussels with the barnacles in some stom- 

 achs suggested that one food was eaten incidentally 

 to the other. In the laboratory, however, green 

 crabs ate barnacles alone; they used their chelae to 

 tear individual barnacles from clusters adhering 

 to wood and glass. The eating of barnacles, thus, 

 was not necessarily contingent upon the ingestion 

 of another food. Occasionally a stomach contained 

 gastropod meats, identified by the presence of a 

 radula but no shell fragments. Green crabs were 

 not seen eating gastropods in the laboratory, but 

 perhaps the snails were eaten in the same fashion 

 as Mya. The crabs usually exposed the meats of 

 3Iya. 10 mm. long or longer by crushing or chip- 

 ping off pieces of the shell with the chelae. Then 

 they easily severed the adductor muscles, tore out 

 pieces of meat, and ate them. Only the largest 

 clams resisted attacks by green crabs. MacPhail 

 et al. (1955) and Dearborn^ found that 3Iya with 

 shells equal in length or shorter than the width of 

 the carapace of a green crab were successfully 

 broken into and devoured. In the laboratory, I 

 saw clams shorter than 10 mm. picked up, crushed 

 by the chelae, and then ingested nearly whole. 

 Many nearly intact valves were found in the 

 stomachs — some in crabs as small as 10 to 19 mm. 

 These results suggested that green crabs probably 

 ate whole animals more frequently than Dearborn 

 believed. Crescent-sjiaped pieces of Sparthia were 

 sometimes found in green crab stomachs. In the 

 laboratory green crabs ate the stems of Spartina 

 by holding them in their chelae so that the mouth- 

 parts surrounded one end. Dow and Wallace 

 (1952) provided additional observations on the 



^ Footnote 1. 



FEEDING HABITS OF GREEN CRAB 



187 



