GEOLOGICAL DISTRIBUTION. 77 



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

 puncta, swarms in countless numbers in a summer following 

 a dry 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 1860 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. Ilartt 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 Ephemeridas, or 

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

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

 fig. 3) ; Lithentomvm Harttii (PL 1, fig. 5) ; Ifomothetus fossi- 

 lls (PL l,fig.*7) ; and Xenoneufa, anti quorum which is supposed 

 to bear a stridulating organ like that of the Grasshoppers, 

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

 roptera in those days." 



Ascending to the Carboniferous rocks, insect-remains appear 

 m6re 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 Clirysopa; with these 

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

 of a caterpillar (Fig. (58), but now thought to belong to 

 some worm. 



