4 BULLETIN 167, U. S. DEPARTMENT OF AGRICULTURE. 



mealworm (Tenebrio molitor L.), and a few others less common are 

 particularly hard to kill when in the adult stage. The larvae of the 

 mealworms, Tenebrio molitor L., Tenebrio obscurus L., and closely- 

 allied species, are likewise found by experiment' to possess great 

 tenacity of life. It is therefore recommended that a proportionately 

 larger amount of para-dichlorobenzene be used when combating these 

 species. Moths, flies, roaches, ants, and aphides are readily killed 

 by para-dichlorobenzene when used in the ordinary strength recom- 

 mended under the heading " Para-dichlorobenzene as an insecticide." 



The action of para-dichlorobenzene on insects is primarily upon 

 their nervous systems. This property is readily manifested when a 

 moth is exposed to the vapors for a few seconds. It first displays 

 great excitement and uneasiness, followed closely by spasmodic con- 

 vulsions, and finally turns ever on its back. While in this position 

 violent nervous and muscular reflex action is noticed until life is 

 extinct. 



The moths on which this gas has been tested include the Angoumois 

 grain moth (Sitotroga cerealella Oliv.), Mediterranean flour moth 

 (Ephestia leuehnietta Zell.), Indian meal moth (Plodia interpunctella 

 Hbn.), meal snout moth (Pyralis farinalis L.), and the case-bearing 

 clothes-moth (Tinea peUionella L.). 



EXPERIMENTS WITH PARA-DICHLOROBENZENE AS A FUMIGANT. 



During the spring of 1914, while stationed at Washington, D. C, 

 the writer, working under the direction cf Dr. F. H. Chittenden, per- 

 formed a series of experiments with para-dichlorobenzene as a fumi- 

 gant for stored-product insects. The chemical was first used on a small 

 scale, and results were afterwards checked up in a specially con- 

 structed air-tight fumigating box having a capacity of 100 cubic feet 

 (PI. I.) The average temperature was computed from the records of 

 a thermograph placed in the box, and the para-dichlorobenzene 

 exposed in shallow piepans or the tops of 5-gallon lard cans, since 

 these shallow receptacles present a much larger surface of the chemical 

 for evaporation. These pans were placed about 4 feet above the 

 material to be fumigated, which was contained in muslin bags of 

 variable capacity (see PI. II) and which had previously been ascer- 

 tained to be free from live insects. Into this material, consisting of 

 wheat, cornmeal, flour, rice, and other cereals, were then introduced 

 living insects, the number and species of each being recorded on an 

 attached tag. 



The respective amounts of para-dichlorobenzene used in each 

 experiment and the tabulated results follow. 



