GEOLOGICAL DISTRIBUTION. 77 



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

 piincta, swarms in countless numbers in a summer following 

 a drj' and warm spring. After a cold and rainy spring, insects 

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

 summer and autumn of ISGO were unusually wet, which dis- 

 abled the bees, wasps, and fossorial hymenoptera generalh*, in 

 building their nests. AVe know how ants are hindered from 

 building their nests b}' rain, and in a very rain}- season luun- 

 bers probabl}' die. A succession of rainy seasons caused the 

 Andrena?, 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 wintei', when it is warm 

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

 to vegetation, should se\ ere 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. Ilartt has discovered near St. 

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

 The}' occur in some plant-beds of the Upper Devonian forma- 

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

 who has refen-ed to them in vol. 1 of the American Naturalist, 

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

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

 He describes a gigantic May-Qy, Platejihemera antiqtia (PL 1, 

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

 lis (PL. 1, 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 and Hemeristia occi- 

 dentalis Dana, allied to Hemerobius and Chrysopa. From the 

 same locality Mr. ITarger has described Arthrohjcosa anVqua 

 (Fig. 68), a singular form with a jointed abdomen. 



