170 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



been waged over them. Yet sufficient is known to have a very 

 distinct bearing upon practical forestry. 



Speuce-gall Aphis. 



On the Spruce the Gliermes appear in the spring as short, 

 oval, wingless insects of an ochreous colour, furnished with a 

 bristle-like rostrum. They have passed the winter in crevices 

 and under bark-scales, and early in April attach themselves 

 each to the base of a young leaf, which reacts by a small swell- 

 ing. These forms are parthenogenetic females, the foundresses 

 of the colony, and lay a mass of eggs at the spot (generally 

 at the junction of two branches) to which they attach themselves. 

 The larvae, hatching, penetrate the surrounding parts of the 

 shoot with their beaks ; the shoot swells, as do the bases of the 

 needles, and a growth commonly known as a " Pineapple-gall " 

 or " Spruce-gall " results. This gall somewhat resembles a small 

 Fir-cone about an inch long, with the surface divided into small 

 convex areas, each bearing a short needle-like projection in the 

 middle ; these are deformed needles, which, becoming swollen, 

 touch each other on the outside of the gall, but which are 

 separate inside, so that the gall contains a series of cavities or 

 chambers. In these cavities the larvse live in numbers, either 

 entering the chambers during the growth of the gall or being 

 enclosed by the swelling of the surrounding needles ; on this 

 point there is a difference of opinion. 



The galls sometimes completely surround the base of the 

 shoot, sometimes they are only developed on one side. The 

 larv^ are closely packed in the chambers, from twenty to fifty 

 being found in each one. When they are fully grown in August 

 they acquire wings and leave the chambers by apertures left by 

 the shrinking apart of the leaves. These insects are winged 

 females, and their special function is that of spreading the 

 species on to other trees. The effect of the galls on the tree is 

 to cause crippling of the attacked shoot, and when they are 

 abundant the general growth of the tree is much impaired. 



Laech-bug. 



The females of Chermes Lands, which also pass the winter 

 under bark, &c., appear in the spring like those of C. Abietis ; 



