GEOLOGICAL DISTRIBUTION. 77 



insect is unusually common. The Army-worm, Leucania uni- 

 juinrfii, swarms in countless numbers in a summer following 

 a dry mid warm spring. After a cold and rainy spring, insects 

 aiv less abundant. Mr. F. Smith remarks that in England the 

 suinnuT and autumn of I860 were unusually wet, which dis- 

 abled the bees, wasps, and fossorial hymenoptera generally, in 

 building their nests. We know how ants are hindered from 

 building their nests by rain, and in a very rainy season num- 

 bers probably die. A succession of rainy seasons caused the 

 Andrenae, or Spring bees, to disappear from the vicinity of 

 London. While a severe winter, if the cold be continuous, is 

 not injurious to insects, mild periods in winter, when it is warm 

 enough to rouse them from torpidity, are as fatal to insects as 

 to vegetation, should severe cold immediately follow. 



GEOLOGICAL DISTRIBUTION. The geological distribution of 

 insects corresponds generally with that of other animals, 

 though insect-remains are few in number, owing naturally to 

 the difficulty with which their fragile forms are preserved 

 in the rocks. Professor C. F. Hartt has discovered near St. 

 John, New Brunswick, the oldest insect-remains in the world. 

 They occur in some plant-beds of the Upper Devonian forma- 

 tion, and consist of six species of Neuroptera. Mr. Scudder, 

 who has referred to them in vol. 1 of the American Naturalist, 

 states that with the exception of one or two Ephemeridte, or 

 May-flies, they mostly represent families which are now extinct. 

 He describes a gigantic May-fly, Platepliemera antiqua (PL 1, 

 fig. 3) ; Lithentomum Harttii (PL 1, fig. 5) ; Homothetus fossi- 

 lis (PL l,fig. 7) ; and Xenoneura antiquorum which is supposed 

 to bear a stridulating organ like that of the Grasshoppers, 

 so that he "is inclined to believe there were chirping Neu- 

 roptera in those days." 



Ascending to the Carboniferous rocks, insect-remains appear 

 more abundant. At Morris, Illinois, have been collected some 

 remarkable forms. Among them are Miamia Bronsonii Dana 

 (PL 1, fig. 1), allied to the White Ants arid Hemeristia occi- 

 dentalis Dana, allied to Hemerobius and Cln-ysopa; with these 

 occurred remains at first supposed by Prof. Meek to be those 

 of a caterpillar (Fig. (>8), but now thought to belong to 

 some worm. 



