42 



A wholesale firin in this city offer to fiiruisli either of the brands of J 

 cyanide mentioned above at the rate of Go cents per pound when pur- 

 chased in quantities. 



The second or drying vessel of the gas generator should be much 

 larger than the one shown in Phite YI of my report. This vessel should 

 be at least 10 inches in diameter. The leaden pipe which conveys the 

 gas from the generator proper to this second vessel should enter one 

 side of the latter near the top and then curve downward until its lower 

 end is within about an inch of the bottom of the vessel. When in use 

 the bottom of this vessel should be covered with sulphuric acid to a 

 depth of 3 inches, and after the gas has passed through it enough of the 

 acid should be drawn out of this vessel to generate the gas the next 

 time, and fresh acid be added to replace that drawn out. 



The generator proper should be furnished with two vessels above, 

 instead of one — one for the acid and the other for the solution. 



EXTERNAL SPIDER PARASITES. 



By L. O. Howard. 



Tn Hardwicke's Science Gossip for July, 1888, a spider from Ceylon is 

 figured with a parasitic Ichneumonid larva in situ upon its back. The 

 adult i^arasite is also figured, and the accompanying note, which is by 

 Mr. E. Ernest Green, of Pnndiloya, Ceylon, states that the Ichneumon 

 appears to oviposit upon the female spiders only, and that the spider 

 continues to feed and remains in apparently good health until the larva 

 is full-grown. The larva then spins a flask-shaped silken cocoon and 

 attaches it to a leaf. IsTo identification of the spider or the parasite is 

 made by Mr. Green, although he states that the latter is possibly allied 

 to the Pimpla mentioned by Packard as being parasitic upon a spider 

 in P^urope. A glance at his figure, however, shows that the parasite 

 belongs to the Ichneumonid genus FoJi/sphiucfa, the species of which 

 are well known to be parasitic upon spiders, their larvie feeding ex- 

 ternally, as pointed out by Mr. E. A. Fitch in the Entomologist some 

 six years ago. xV similar case in America was for the first time men- 

 tioned by the writer in a communication to the Entomological Society 

 of Washington, not yet published. In this case the parasitic larva 

 was apparently less than half grown, and it was killed without rearing 

 the adult. The specimen was captured by Dr. W. 11. Fox, of Wash- 

 ington, in February, which would indicate a larval hibernation of the 

 parasit(\ Dr. Fox's larva differed greatly from the full grown Pol}/- 

 sphincta larva as figured by I^itch, but this may be due to the fact that 

 it had not reached hall" its ultimate size. The spider upon which it 



