62 



While the writer does not attempt an explanation of the difference 

 in results obtained with the same insecticide in the two cities, it is 

 possible that one may be found in the fact that the insecticide, being 

 applied as a spray to the the trees in Holyoke, reached more of the 

 limb surface and killed a greater percentage of the insects than did the 

 application with whitewash brushes in Springfield. 



At the time of the writer's visit to the trees in Springfield on July 

 20 the adult females were laying eggs and a part of those laid had 

 already hatched. The young lice, however, had not migrated far, being 

 still clustered around the parent insect. In the cottony masses envel- 

 oping the eggs and crawling about over the leaves and branches were 

 great numbers of the larvae of the Ooccinellid beetle, Ryperaspis signata. 

 These larva3 were feeding voraciously on the eggs, larvse, and adults of 

 Pseiiclococcus aceris. Fully 75 per cent of the cottony egg masses which 

 I saw contained either a larva or a pupa of the beetle or had been 

 devastated and abandoned. Dr. Howard has already recorded this bee- 

 tle as an enemy to Pseudococcus aceris in Insect Life, Vol. VII, page 

 239. Desiring to learn if the beetle had appreciably reduced the col- 

 ony of the Coccid, the writer paid another visit to the city on August 

 6, as has already been stated, and found that a remarkable change had 

 taken place. A majority of the trees had only here and there an 

 infested leaf, while others showed no signs of the insect whatever. 



The " imported elm bark-louse," Gossyparia ulmi, is a very widely 

 distributed and well-established enemy to elms in the State, ranking in 

 importance second to none, with the possible exception of the San Jose 

 scale. It is a noticeable fact that as common as this insect is in Mas- 

 sachusetts, with very few exceptions it has never been sent to the 

 experiment station at Amherst. An explanation of this may be found 

 perhaps in the fact that the species, being fixed to the bark and some- 

 what resembling the lichens on the tree, bears but little resemblance to 

 what the ordinary observer recognizes as an insect. Were legs and 

 antennas visible, and did the creature move, without doubt it would 

 more often be recognized as a pest. 



This difficulty in detecting the insect is obviously an important factor 

 in the problem of its control. It is often the case that a tree or row of 

 trees infested with the species is known to be turning yellow or losing 

 here and there a limb, while the owner sees no cause for the damage 

 and takes no action. Meanwhile the trees are being destroyed and the 

 pest is spreading. Precisely these conditions existed in a block of a 

 number of thousands of elms in a large nursery located at Concord. 

 The owner was aware that the trees were in a sickly condition, but did 

 not know the cause, until the writer, visiting the nursery, called his 

 attention to this insect, which was there in great numbers. 



As has been stated by many authors, trees previously weakened by 

 other causes are more liable to be attacked by this insect than those 

 which are healthy. The writer has observed that trees located in the 



