45 



THE ARMY WORM. 

 (Leucania unipuncta Haw.) 



With the rapidly increasing area of low, wet lands, which are being 

 under-drained and brought into cultivation, the natural haunts of this 

 species becomes more and more encroached upon. What the ultimate 

 effect of this change of natural conditions will amount to in the future, aud 

 whether or not it will have a tendency to scatter the spring brood of 

 moths in their selection of places of oviposition, only future years will 

 answer. In accordance with the characteristic partiality of the species 

 for low, damp localities, the outbreaks in Indiana this year have been 

 restricted to the lower laying and flatter portions of the State, where a 

 very considerable part of the land remains undrained, except by open 

 ditches. While this state of affairs has been going on, the fact that dry 

 seasons are favorable to the increase of the species has been amply 

 demonstrated. The last two summers have been unusually dry, and 

 the spring of the present year, up to May 30, was exceedingly dry, mak- 

 ing three consecutive years of drought, during all of which this pest has 

 appeared in various portions of the State, the maximum injury being 

 caused the present summer. During this period, also, we have had wet 

 springs and dry summers and dry springs and wet summers, proving 

 conclusively that wet weather has little if any direct influence upon the 

 increase or decrease of numbers. In short, it is difficult to resist the 

 suspicion that this ebb and flow, so to speak, may be due more to the 

 fluctuation of natural enemies than to the direct influence of meteoro- 

 logical conditions, severe droughts excepted. 



In the vicinity of Princeton, Ind., where considerable damage was 

 done last year, there occurred this season only one weak, aborted out- 

 break, in a small field of rank growing timothy grass. A slight attack 

 three years ago on the borders *>f a large tract of swampy land in 

 the vicinity of La Porte, Ind., was not followed by others, either last 

 season or this, although this year similar and more serious outbreaks 

 occurred in that immediate section of the State, and within a few miles 

 of the same locality. Such phenomena can not be wholly attributed to 

 meteorological conditions, most certainly. The most efficient parasites 

 of the army-worm are two species of Tachinw, and we have reared both 

 plentifully this season. The local effects of these parasites is probably 

 more lasting than we are given to suppose. A circumstance came under 

 our observation recently where the attack of a similar species of Tachina 

 on the larvas of Batana ministra, infesting an isolated walnut tree, was 

 such that the tree has been free of the caterpillars since 1885. If the ef- 

 fects are equally lasting in the case of the army- worm it will be difficult 

 to foretell their appearance in dangerous localities, even in seasons sup- 

 posed to be most favorable. 



Again, the secret of the power of the army-worm to destroy is in their 

 massing together in endless numbers. Were it not for this they would 



