396 INSECTS OF MASSACHUSETTS. 



themselves comfortably bedded within the pulpy tumors, and 

 plentifully supplied with food on every side. They feed on the 

 vegetable substance immediately around them, come to their 

 growth in due time, cast their skins, and appear first in the chrys- 

 alis and then in the winged form, and finally gnaw their way 

 through the hard shell of the galls, and come out into the open 

 air. There are a few of the grubs, however, that leave the galls 

 when fully grown, and finish their transformations in the ground. 

 The grubs or young of the gall-flies are of a whitish color, and 

 somewhat resemble maggots, but are shorter and thicker, and have 

 a small, distinct head. They are without proper legs, and move 

 only by means of the swollen edges of their rings, with the aid, 

 it is said, of certain little contractile warts, on their bodies, that 

 serve them instead of feet. There are almost as many kinds of 

 galls as there are species of gall-flies ; and each species confines 

 its attacks to some one sort of plant, and to some particular part 

 thereof. It is wonderful that there should be such a diversity in 

 the forms and texture of the galls of insects so nearly resembling 

 each other in form and structure ; and, on the other hand, that 

 each species of gall-fly should invariably produce galls of the 

 same kind. Many galls are very irregular and uneven, others are 

 round and resemble fruits ; some are smooth, others are beset 

 with prickles, or covered with a woolly substance ; some hang by 

 little stems, others are perfectly flat, and adhere closely to the 

 surface of leaves. At first they are soft or spongy within, but, 

 after some time, they become hard and almost or quite woody. 

 The eggs of some gall-flies do not hatch till the galls begin to 

 grow hard on the outside ; this is the reason why we do not find 

 any insects within certain kinds of galls, so long as they remain 

 soft and unripe. Of this description are the galls called swamp- 

 apples and cedar-apples. The former grow on the small twigs 

 of the swamp-pink, or Azalea viscosa ; they are irregular in 

 shape, of a greenish while color, and fleshy consistence, like an 

 apple, and are sometimes eaten, but are rather too astringent to 

 be pleasant. Cedar-apples are found on the twigs of the red 

 cedar (Juniperus Virginiana)] in their unripe state they are 

 large, irregular, and coarsely fringed lumps, of an orange color, 

 and as soft as jellv ; they afterwards shrink, become hard and 



