JOURNAL OF PROCEEDINGS. 159 



Rep. Pacific Railroad Surveys, Vol. XII., Pts. I. & II., 4to, 1860, from 

 the Hon. Trusten Folk; Bull, de la Soc. Imp. zool. d'Acclimatation, Paris, 

 T. VIII., No. 4, April. 18(31, from the Society ; Proc. Entomological Soc, 

 Philad., Mar.-May, 1861, from the Society; Proc. Boston Soc. Nat. Hist, 

 April & May, 1861, from the Society. 



Dr. H. A. Prout presented a paper for publication, entitled 

 "New Species of Uryozoa, 5th series, containing descriptions 

 of Fenestella nodosa, F. dilatata, F. bifurcata, and Hetepora 

 Jlamiltonensis. 



July 1, 1861. 



The President, Dr. Engelmann, in the chair. 



Seven members present. 



Dr. Wislizenus communicated the following remarks on 

 the so-called " army worm :" 



This insect now devastating our fields is, properly speaking, a cater- 

 pillar, described in works on Natural History as Bombyx graminis or 

 grass caterpillar. Its destruction of grass fields is dreaded as much in the 

 North of Europe as in this country. In Sweden and Norway these 

 insects in some years eat off the grass so thoroughly that not a blade is to 

 be seen It made its appearance in St. Lcuis county in the early part of 

 May, and is now gradually leaving us. On a farm near the city, where I 

 observed its mode of life, it showed a decided predilection for timothy, of 

 which it left only the lower part of the bare stem, giving it the appear- 

 ance of a field of rushes. Timothy growing on high ground was less 

 attacked by them than that growing on low ground. In lack of timothy, 

 they devour Hungarian and blue grass, and the young shoots of all cere- 

 als, even Indian corn. 



Their numbers seem to diminish, not because they die, as many sup- 

 pose, but. because their time has come to be changed into the chrysalis 

 state. For this transformation the caterpillar hides itself superficially 

 under the ground, and lies there for awhile, in a torpid, contracted state, 

 until it is changed into a small brownish pupa, from which in a couple 

 of weeks a butterfly is developed, a dark brownish moth. This moth, 

 during its short life, lays numerous eggs on and below the ground, 

 to preserve the grass-caterpillar for the next spring, when the young 

 army-worms will, as by magic, come forth in a new generation. From 

 the millions of eggs which tne moths will lay this summer, it is feared by 

 some that we may be overrun next spring by a still larger levy of the 

 army-worm. But this is by no means certain. Experience, on the con- 

 trary, has proved that such a year of warfare upon our fields is generally 

 followed by a peace of many years, since it requires peculiar climatic 

 influences to develop these insects so freely. Their development is 

 favored by a dry and warm summer, followed by a mild winter. In such 

 years two generations of those insects will sometimes be procreated in 

 one year ; at any rate they thrive better, and millions of eggs that would 

 otherwise perish are preserved in such years. The insect, with its 

 regular transformation from the egg into the caterpillar, the pupa and the 

 butterfly, or moth, exists always, but in some years they are nearly 

 all killed ; in others they are preserved and developed by climatic influ- 

 ences. Such influences, favorable to their preservation, exis'ed last year 

 and this spring. After a warm and dry summer and a mild winter we 

 had a fine spring, with gradual development of heat and frequent warm 

 rains, influences that not only aid vegetation, but also the existence of 

 insects and lower animals generally. But since the exact repetition of 



