GALLS INDUCED BY PLANT-LICE 79 



They resemble immature cones in size and shape, and are 

 often alhided to as " Pineapple " galls. It has been dis- 

 covered within recent years that several insects were at one 

 time comprised under the name of Chermes abietis, and even 

 now there is much that is obscure concerning their life- 

 history. 



In the true Chermes abietis the life-cycle is confined to the 

 alternation of two parthenogenetic generations on the Spruce. 

 The larva hatched from an egg in autumn pierces a bud or 

 its vicinity with its long proboscis, and thus firmly anchors 

 itself for the long winter sleep. These larvae, or fundatrices, 

 as they are often termed, may be easily found in winter 

 by carefully examining the base of the shoots with a good 

 pocket-lens. They are a dirty -yellow colour. In spring, 

 about April — but the time depends upon meteorological con- 

 ditions — without moving its position, the Fundatrix begins to 

 suck, and attains maturity in about a month. It undergoes 

 three moults, one every ten days or thereabouts. As soon 

 as it begins to suck, and not before, precocious growth 

 arises in the cells in the neighbourhood of the cambium, at 

 the point where the apex of the deeply buried proboscis lies, 

 and spreads rapidly outwards. In the early stage there is 

 little or no external evidence of altered growth, but a section 

 cut through the bud will at once reveal it : the affected part 

 looks bleached. Later the needles become swollen at the 

 base. Being closely crowded they quickly begin to press 

 upon one another, and four grooves result at the base of 

 each needle. As elongation proceeds, the needles separate 

 slightly, leaving a space above each. These spaces are 

 afterwards occupied by the larvae. At this stage the gall 

 is easily seen with unaided vision. In the meantime the 

 Aphis has been steadily sucking and waxing fat, at the same 

 time secreting much white, waxy, wool-like matter which 

 covers her up, yet makes her presence more apparent. She 

 has undergone her three moults (ecdyses) and arrived at 

 maturity. It is now about the second week in May, and 

 she commences to lay her eggs, continuing to do so through- 



