GEOLOGICAL ANTIQUITY OF FLOWEKS AND INSECTS. 
45 
larvse. One species of Thrips has been found whose minute 
fringed wings, characteristic of its order, are visible under the 
microscope. Fossil ants occur here, so that their peculiar 
specialization had already been effected. Only one species of 
moth, however, has hitherto been met with out of the sixty or 
seventy fossil insects described. 
Later tertiary beds always contain fossil insects where the 
conditions are favourable to their preservation ; but it would 
appear as if all the great orders had assumed their modern distinc- 
tiveness before the close of the Miocene period. What has since 
occurred has been chiefly their changed geographical distribution, 
and the breaking up and differentiating of two of the orders, 
Hymenoptera and Lepidoptera, so as to adapt many of the 
species of each to the most abundant or most frequented of the 
flowers where such insects have been distributed. 
We see that a comparison of the order in which insects 
have appeared leads us to infer the absence of true flowers 
until the later geological epochs. A parallel development 
has taken place in insects and flowers during geological times, 
so as to slowly and mutually adapt each to the other. The 
order in which the various families of flowering plants have 
appeared bears a relation to that in which the different groups 
of insects have succeeded each other. Thus we have first the 
conifers and cycads, wind-fertilized plants, producing a super- 
abundance of pollen so that some of it may surely take effect. 
The grasses and sedges probably appeared during the Triassic, 
Liassic, and Oolitic periods, although in no very great abun- 
dance or variety, or we should have more fossil remains of them 
than we have in the doubtful Cyperites. The Antholithes of the 
coal measures, once believed to be a grass, is now known to be 
merely a fruit-bearing spike of some coniferous plant. During 
the “ age of conifers ” a large differentiation took place in this 
order. There were coniferous trees living during the Carbo- 
niferous period which bore adiantum-like leaves, similar to those 
still produced by the peculiar conifer from Japan known as 
Salisburia , and 64 stone fruit,” almost like plums, or rather 
resembling the fruit of the yew, which has long been familiar 
to geologists under the name of Trigonocarpum. These fruits 
are found in such abundance in some sandstone beds of the 
Upper Coal Measures as to make them appear almost composed 
of nothing else. Pines with the ordinary needle-shaped leaves, 
and cone-bearing, have always been abundant. The fossil plant 
known as Pothocites , found in the Scottish Coal Measures, and 
supposed by Carruthers to be the spike of an aroideous species, 
is imperfect, and some botanists deny its phanerogamous 
character altogether. Only eighteen species of fossil monoco- 
tyledonous flowering plants are recorded as having been dis- 
