FRAGMENTS OF SCIENCE. 



xrf 



Ups and Downs of the Tnssoek Moth. 



After the English sparrows had quite ex- 

 terminated the voracious measuring worms 

 that used to make our city trees naked, the 

 uneatable tussock moths took advantage of 

 the opportunity and filled the trees for a few 

 years with their uneatable larvae. Now the 

 tussock moths have nearly disappeared, and 

 A Study in Insect Parasitism, by L. 0. How- 

 ard, entomologist of the Department of Agri- 

 culture, tells us how it came about. It ap- 

 pears to be a kind of process of Nature that 

 as soon as any living thing becomes numer- 

 ous parasites find it, and shortly reduce it to 

 its normal proportions or below. These in 

 turn are subject to secondary parasites which 

 keep them in check. Thus twenty one para- 

 sites have been found upon the tussock moth, 

 with fifteen hyperparasites. While, after 

 having passed its culmination in the farther 

 Eastern cities, the proportion of tussock 

 moths has been about the same, it took a 

 rapid and enormous increase in Washington 

 in 1895. But the parasites appeared in force 

 with the third generation of that year ; and 

 when in September several species of trees 

 had been cleared of leaves and others badly 

 injured, " it was an exception to find a 

 healthy caterpillar which one of them was 

 not engaged in stinging." There was a 

 moderately abundant hatching of caterpil- 

 lars in 1896, but the parasites were ready for 

 them, and the first generation was practically 

 exterminated by them. In the later months 

 of 1896 the hyperparasites took their turn, 

 and the tussock-moth caterpillars were not 

 so hard to find, but were still rare. Even 

 where parasites do not step in to keep down 

 increase, the excessive multiplication of ani- 

 mal pests is at length inevitably checked by 

 disease. Thus the chinch bug has no para- 

 sites, " but when it increases beyond the 

 bounds of what may be called Nature's law, 

 for want of a better term, bacterial and fun- 

 gous diseases speedily carry it off." 



Objects of National Forestry. The policy 

 and aims of those who are peeking the es- 

 tablishment and maintenance of a national 



forest policy have been misunderstood and 

 misrepresented; and the misapprehension 

 has been strengthened by some glaring de- 

 fects in some of the forest laws, which the 

 friends of forestry do not approve and desire 

 to have remedied. It is not by their work, 

 but contrary to their intentions, that these 

 laws embody no provisions by which citizens 

 can obtain wood from the public domain by 

 purchase, and that timber- stealing flourishes 

 under their operation. The laws which they 

 propose are designed to remedy these evils. 

 Reservation is the first purpose sought in 

 them, regulation of the use of the timber the 

 second ; perpetuation of a valuable resource 

 for coming generations the object. The pro- 

 gramme of those urging these laws, as de- 

 fined by Mr. B. F. Fernow, chairman of the 

 American Forestry Association, is to with- 

 draw from sale or entry all lands not fit or 

 needed for agriculture and to constitute as 

 objects of special care by the Government 

 the lands at the head waters of streams and 

 on mountain slopes in general; to permit 

 prospecting, mining, and other operations 

 under such regulations as will prevent un- 

 necessary waste, and to cut and sell the tim- 

 ber under such methods as will secure per- 

 petuation and renewal of the forest growth ; 

 to provide for protection against fire, theft, 

 and unlawful occupancy ; to respect all exist- 

 ing vested rights and arrange an exchange, 

 if necessary, for private lands included in 

 reservations ; and, finally, to restore to the 

 public domain for entry all lands that are 

 found in the reservations fit for agriculture. 

 The interests of the miner, the lumberman, 

 the settler, and every citizen in the present 

 and the future are regarded in the policy they 

 advocate ; the free herding of sheep, by 

 which forest tracts are destroyed and ren- 

 dered unfit for renewal, being the only indus- 

 try not considered. " Just like the proverbial 

 incompatibility of the goat and the garden, 

 the growing of wool and wood on the same 

 ground is incompatible." 



Sewage Purification by Filtering. Fil- 

 tration through the soil is regarded by M. 



