GEOLOGICAL DLSTRIBUTION. 77 



insect is unusually common. The Army-worm, Lencania iini- 

 2-)nncta, swarms in countless numbers in a summer followino- 

 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- 

 al)led the bees, wasps, and fossorial hymenoptera generally, iu 

 l)uilding their nests. We know how ants are hindered from 

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

 bers probably 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 winter, when it is warm 

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

 to vegetation, should se\ere cold immediately follow. 



Geological DLSTniiuTTiON. The geological distribution of 

 insects corresponds generally with that of other animals, 

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

 the difficulty with whicli 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 Neurojitera. Mr, Scudder, 

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

 states that with the exception of one or two Ephemerida?, or 

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

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

 fig. 3) ; Lithentomimi Harttii (PL 1, fig. 5) ; Homotlietus fossi- 

 lis (PI. l,fig. 7) ; and Xenoneura cmtiqiiorum which is supposed 

 to bear a stridnlating organ like that of the Grasshoppers, 

 so that he ''is inclined to believe there were cliirping 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 

 (PI. 1, fig. 1), allied to the White Ants and Hemeristia ocd- 

 dentalis Dana, allied to Hemerobius and Chrijsojxi. From the 

 same locality Mr. Ilar-^c-r has described Arthrohjcosa antiqua 

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



