F. M. Carpenter.
Early Insect Life.
Psyche 54(2):65-85, 1947.

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PSYCHE
VOL. 54 JUNE, 1947 No. 2
EARLY INSECT LIFE*
BY FRANK M. CARPENTER
Harvard University
Most entomologists, whether concerned with insect con- trol or taxonomy, are convinced that we have enough living insects to contend with, without bothering about those of prehistoric times. Paradoxical as it may be, how- ever, man apparently owes his very existence to the early insects. Some three hundred million years ago, as the first Amphibia abandoned the aquatic environment of their ancestors and explored the possibilities of terres- trial life, they were obliged to find a new source of food. By that time, the insects had already become established on land and, being especially abundant near water, were readily available to them. The amphibians were thus able to survive in their new environment and eventually their descendants gave rise to reptiles, birds and mam- mals,. Many geologic periods later-only a few million years ago, in fact-man evolved within the mammalian complex. Cannot the insects claim, therefore, that if it were not for their early ancestors, the vertebrates might have failed to gain a foot-hold on land and man might not have come into existence?
Let us consider the nature and extent of the early insect life to which we presumably owe so much. "Early" is of course a relative term, and to define my present use of it, I must refer to the conventional geologic timetable. Figure 1 lists the eras and periods of that part of geologic time with which paleontology is chiefly concerned. Of the three eras, the Paleozoic is the earliest and longest, * Annual Public Address of the Entomological Society of America, Rich- mond Virginia, December 9, 1946. Published with the aid of a grant from the Museum of Comparative Zoology at Harvard College. 65
Pu&e 54:&85 (1947). hup Ytpsychu einclub org/S4/54-065 html



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66 Psyche [June
beginning about 550 million years ago and extending up to some 190 million years ago. For convenience, it is divided into six periods of unequal duration, their limits being arbitrarily set with reference to extensive geologic events. In this account of early insect life, I am refer- ring only to the insects of the Paleozoic era-from the first appearance of the group through the Permian Period.
The question of the oldest geologic occurrence of any group of organisms is always a controversial one, for much depends on interpretation of fragmentary material TABLE OF GEOLOGIC PERIODS
APPROXIMATE TIME
ERA 1 PERIOD
1 IN MILLIONS OF YEARS)
SINCE BEGINNING
OF PERIOD
CENOZOIC QUATERNARY
(AGE OF MAMMALS AND MAN)
T~RTIARy 1 6;
TRIASSIC 35
PERMIAN 1 25
PALEOZOIC
(AGE OF INVERTEBRATES AND
PRIMITIVE VERTEBRATES)
DEVONIAN
SILURIAN
ORDOVICIAN
Figure 1. Table of ~eolo~ic Periods. (Adapted from Rorner's Verte- 'brute Paleontology, University of Chicago Press.) and the definition of the group.
Handlirsch showed in
1906 that the fossils described as insects from strata older than those of the Upper Carboniferous Period were not insects at all; and he concluded that the earliest record of the class was in the lower part of that period. During the past forty years discovery of three older insects has been announced. Two of these, identified as Collembola, have been described from Devonian rocks, the Rhynie Chert, of Scotland.' Without going into details, we can 1 R. J. Tillyard, Trans. Ent. Soc. London, 1928: 65-71; H. Womersley, Victorian Naturalist, 1934, vol. 51: 159-165; D. J. Scourfield, Proc. Linn. Soc. London, 152 sess., 1939-40 : 113-131.



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19471 Early Insect Life 67
state that these fossils are very fragmentary, the largest specimen being only about a millimeter long. Many parts of the head and thorax have been found, but since only the first three abdominal segments are known, there is no evidence that the collembolan "spring" was present, or that the abdomen consisted of but six segments, as in living Collembola. Consequently, although such eminent authorities as G. H. Carpenter and H. Womersley have accepted the specimens as Collembola, I believe that doubt about their relationship will exist until additional fossils have been found showing those two characteristic fea- tures of the Collembola. As a matter of fact, as Imms and others have pointed out, the Collembola are not true insects-that is, although hexapodous arthropods, they arose independently from pre-insectan types. The possi- ble occurrence of Collembola in Devonian rocks, there- fore, has no direct bearing on the earliest record of true insects.
The other discovery of an insect in rocks older than the Upper Carboniferous was announced by the French paleontologist, Dr. Pierre Pruvost, in 1919. The speci- men concerned was found in Lower Carboniferous strata of Nova Scotia (Horton's Bluff), and identified by Pru- vost as a member of the extinct Order ~a1ffiodict~o"ptera.~ However, examination of this fossil, which is now in the Peabody Museum at Yale University, convinces me that it is in reality part of a plant stem. A similar conviction was expressed by Dr. David White,3 then paleobotanist of the United States Geological Survey, who studied the specimen shortly after it was found, although he did not publish his conclusion.
According' to our present knowledge, therefore, the earliest unquestionable insects occur in Upper Carbon- iferous strata. This first occurrence is not extensive, but it does indicate the approximate time of origin of the insects. Let us return for a moment to the geologic time- table, and examine in more detail the Upper Carbonifer- ous Period (Figure 2). This represents an interval of 2 La Faune continentale du terrain Houiller du Nord de la France, p. 283. 3 In a letter dated May 11, 1914, and on file in the Peabody Museum.



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PERIOD STAGES
Psyche [June
INSECT ORDERS
Coleoptera
Thysanoptera, Perlaria
Protope~la~ia, P~otelytroptera~
Ephemerida, Odonata,
Corrodentia, Hemiptera,
Mecoptera, Neuroptera
Megasecoptera, Calonewodea
Palaeodictyoptera, Blat taria
Protodonata, Protorthofitera
Figure 2.
The First Occurrence of Insect Orders in the Permian and Carboniferous Periods.
Names of exinct orders are italicized.




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19471 Early Insect Life 69
about thirty-five million years, and on the basis of its flora and fauna, is divided into three main stages, the Upper Namurian, Westphalian, and Stephanian. The record of insects is very scanty in the oldest of these; not until the late Westphalian and Stephanian rocks are insect re- mains sufficiently abundant and preserved to give us a concept of the fauna. Nevertheless, three species are known from the Upper Namurian, at the very base of the Upper Carboniferous, and they constitute the earliest record of the insects. One of these (Emsiptern Zarischi Pruvost), from Czechoslovakia, consists of part of a wing, which, though incomplete, clearly belongs to a member of the extinct Order Protodonata, related to the Odonata. Another fossil (Stygne roemeri Handl.), from Germany, is a nearly complete wing with orthopteroid features that place it in another extinct order, the Protorthoptera. The third specimen (Metropator pusillus Handl.), from Penn- sylvania, is a very fragmentary wing which might have belonged to any one of several orders. Now this is truly a meagre record, but it does reveal two facts : first, insects with fully developed wings existed in the earliest part of the Upper Carboniferous Period, about 250 million years ago; and second, at least two orders, widely separated phylogenetically, occurred at that time. We can infer from this 'ecord that insects must have arisen at least as far back as the Lower Carboniferous in order for such di- versity to be attained by the beginning of the Upper Car- boniferous. This inference becomes even more obvious, when we bear in mind that morphological studies have shown that the most generalized or primitive insects were wingless, like the Thysanura. Apterous species must have existed, therefore, even before the winged ones. So much for the first record of the insects. Let us now
briefly consider the development of the class during the rest of the Paleozoic era. Referring again to the Upper Carboniferous table (Figure 2) we find that as we go up through the several stages, additional orders appear, and there is an increase in the total number of orders. From the lower half of the Westphalian stage (A and B) there are forty species known, representing the two orders



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70 PsYc/%~ [June -
previously mentioned (Protodonata and Protorthoptera), as well as the extinct order Palaeodictyoptera and the existing order Blattaria or cockroaches. In the upper half of the Westphalian stage (C and D), about 15 million years after the first record of the insects, we come to the level of the Mazon Creek nodules in Illinois, second only to the Commentry shales in France as a source of Carbon- iferous insects. From this part of the Westphalian more than four hundred insects are known, representing the four orders already mentioned and in addition two other extinct ones, the Megasecoptera and Caloneurodea. From the Stephanian stage, which includes the Commentry de- posit, about fifteen hundred species have been described, belonging to the orders previously mentioned as well is still another exinct one, the Protohemiptera. Thus, we see that by the end of the Upper Carboniferous seven orders of insects had come into existence, of which one, the Blattaria, survived for some two hundred forty mil- lion years to the present time.*
Let us now continue into the Permian Period (Figure Z), which represents an interval of about twenty-five mil- lion years. In the lower or oldest strata of the period eight orders have been found in addition to the seven which have persisted from the Carboniferous. Two of these, the Protoperlaria and Protelytroptera, are extinct, but the others are living orders. These are the Ephem- erida, Odonata, Corrodentia, Hemiptera, Mecoptera, and Neuroptera. This fauna was an extremely interesting one, combining as it did eight extinct and seven existing orders. The Lower Permian was the last time, so far as our records now show, that the extinct orders out- numbered the existing ones. In Middle Permian rocks, Thysanoptera and Perlaria have been found.; and in upper Permian strata the Coleoptera appear. These make a total of eighteen living and extinct orders of insects which came into existence before the end of the Paleozoic era, about two hundred million years ago ; and of these ten are still living.
4 I have not included in this account several extinct orders which are based upon very fragmentary specimens.




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19471 Early Insect Life 71
This brief survey gives an idea of the extent of the early insect life. The fauna was obviously a complex one- probably more so than we fully realize, for our present roster of the orders existing at the time is surely far from complete. Nevertheless, the variety of insect types proba- bly fell far short of that which exists now, their biological environment being relatively simple. The plants of the time were largely seed-ferns and other gymnosperms ; angiosperms were entirely absent, and, incidentally, did not arise for many millions of years later. It is difficult for us, living at a time when angiosperms dominate the plant world, to imagine a time of their complete absence; and equally difficult to imagine an extensive insect fauna without them. Also, there was a complete absence of birds and of mammals. Insects were then the only flying creatures on earth; they could readily escape by flight from their amphibian and reptilian enemies without danger of pursuit. Certainly the life of the insects must have been very different then from what it is now-with birds, bats, man, and DDT.
Our knowledge of the habits, life histories, and food of these early insects is necessarily slight, but certain infer- ences can be made from their structure, as we now know it. Let us see what this was like and what conclusions can be reached.
The order Palseodictyoptera, which existed during the Upper Carboniferous and Permian, is a negative and ill- defined group. Attempts to divide it into two or more orders have not proven successful, because some species seem to merge into the Ephemerida, and others into the Orthopteroids. Nevertheless, I believe that most of the one hundred fifty species which have been described are members of one order. Their closest living relatives are the Ephemerida and, to a lesser extent, the Odonata. The fact that all complete specimens are preserved with their wings outspread shows that, like the Ephemerida and Odonata, they were palaeopterous, i.e., unable to fold their wings back over the abdomen at rest. They had nearly similar fore and hind wings and were apparently weak fliers. Although they are mostly preserved as isolated



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72 Psyche [June
wings, enough whole specimens have been found to give us a slight knowledge of their body structure. They were
primitive insects, probably more so than any other known winged insects, but they did have some specializations. It should be noted, in this connection, that no remains of bodies of any insects have been found in the older half of the Upper Carboniferous strata.
Not until "we come to the
Mazon Creek deposits, about 15 million years after the first record of the insects, are body remains known. This
probably would have provided ample time for extensive specialization to develop. At any rate, the Palseodicty- optera were more primitive than any winged insects now living.
They show about the same range in size as living dragonflies, many having a wbg expanse of about two inches.
The head was relatively small; the mouth-parts mandibulate and inconspiauous.
Their antennae are un-
known, except for the proximal segments ; probably they were moderately long and multisegmented. The thoracic
segments and legs were nearly homonornous. The most striking characteristic of the Palseodictyoptera was the presence of paired membraneous lobes on the prothorax ; these resembled miniature wings and are usually con- sidered homologues of the functional meso- and meta- thoracic wings. The abdominal segments showed little differentiation, and the abdomen terminated in a pair of long, multisegmented cerci.
Well preserved specimens
have paired lateral lobes on each abdominal segment. The immature stages of the Palaeodictyoptera, are com- pletely unknown. Several vague and fragmentary speei- mens, which are probably insect nymphs of some sort, have been assigned to the Palseodiet~optera, but they could just as well belong to certain other groups. The paired abdominal lobes of the adult have been generally interpreted as vestigial tracheal gills of the nymphs. This of course implies that the nymphs were aquatic; and in view of the close relationship between the Ephemerida and Odonata, both of which have aquatic nymphs, we may infer this to have been the case. From this vou will see that our knowledge of the Palseodictyoptera is not great. Their general activities were probably much like those of



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Early Insect Life
the present-day may-flies, crawling and fluttering among the plants bordering the ponds or swamps in which their nymphs developed-inoffensive creatures whose only claim to fame is their antiquity and proximity to the great ancestor of all insects. They had no defense against the more powerful, predaceous insects which developed dur- ing the later Carboniferous and Permian, and for which they must have been easy prey.
Related to these Palseodictyoptera was another order of ephemerid-like creatures, termed the Megasecoptera. They were small to large insects, with a wing expanse ranging from one-half to five inches, and, like the Palseo- dictyoptera, they were unable to fold their wings over the abdomen. Until about 12 years ago they were known exclusively from the Upper Carboniferous; many Per- *
mian species have since been found, and it has become apparent that the order did not attain its greatest devel- opment until that period. They had moderately long an- tennae, and extremely long cerci. In the Carboniferous- species the head was small and short, but in some of the Permian types it was prolonged into a rostrum, probably much like that of the scorpion-flies. The older forms had mandibulate mouth-parts, and this was probably true also of the later species. The thorax and abdomen were slender, and, in the main, generalized in structure. In certain Carboniferous species, however, the prothorax was highly modified, bearing conspicuous projections or spines, which may have had some protective value. The legs of most were of the ordinary walking type, but in one Carboniferous genus (Mischoptera) the fore legs were short and raptorial in form though there are no other indications of predaceous habits. The wings were the most characteristic structures of the Megasecoptera. In most species they were very narrowed basally, and in one family they were arcuate, as in many families of living insects. Two abdominal structures are noteworthy : the very elongate cerci, which surpass in length those of most other insects ; and, in certain families, lateral gill-like proc- esses, resembling those of the Palseodictyoptera. Nothing is known of the immature stages of the Megasecoptera, but



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74 Psyche [June
the presence of the supposed gill-vestiges just mentioned suggests that at least some of them had aquatic nymphs. The Megasecoptera were probably no better fliers than the Palaeodictyoptera, and their long cerci must have handicapped them in their attempts to escape from ene- mies. Perhaps this had something to do with their abrupt disappearance at the close of the Permian, for no sign of them has been found in later strata.
We next come to the insect dinosaurs-the Protodonata. These include the largest insects known, living or extinct. Although all species were large, as insects go, not all were giants, as is usually stated; some had a wing expanse of five inches, which is well within the limits of many living insects. Three very large species have been found, all belonging to the family Meganeuridae. One, from the Carboniferous of France, was about twenty-six inches across the wings; the other two, from the Lower Permian of Kansas andOklahoma, were somewhat larger, with a wing expanse of about thirty inches. The distribution of these species, both in space and time, indicates that the giant meganeurids inhabited an extensive area of the earth for some fifty million years, though the whole order became extinct shortly after the close of the Permian Period. The protodonates resembled dragon-flies in gen- eral appearance, and the earlier forms were probably directly ancestral to the true Odonata. They had large, toothed mandibles and spiny legs, and were undoubtedly predaceous. What they fed on, we can only guess. The contemporary slow moving Palaeodictyoptera and Mega- secoptera, which, because of their wing structure, were unable to hide easily among plants or under rocks, were probably their chief source of food. Protodonate nymphs , are unknown. They were probably aquatic, although Dr. August Krogh has asserted that nymphs of the giant meganeurids could not have breathed through caudal or rectal tracheal gills, as odonate nymphs do, since in order to convey the necessary quantity of oxygen to the head, their trachea would have required a cross-section greater than that of the body itself.
However, passage of oxy-
gen in the tracheae might well have been sufficiently a,ided



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19471 Early Insect Life 75
by muscular movement to make this mechanism practical. At any rate, the adult Protodonata and Odonata are so much alike, I find it difficult to believe that their nymphs were very different.
The insects which we have been considering so far are primitive types which we would expect to find as part of early insect life. The group we are now to discuss is not in this category. For although their wings were of the palseopterous type, the head was modified into a long rostrum, with suctorial mouth-parts. The best preserved specimen (Eugereon) of this group has been found in Upper Permian rocks of Germany, but other representa- tives, also with elongate beaks, have been collected in Carboniferous strata of France, Belgium, and England. Since these insects were at first thought to have been related to the Hemiptera, Handlirsch termed the order the Protohemiptera. The choice of name was unfortu- nate, for, with the discovery of new specimens, it has become increasingly clear that they had nothing to do with the Hemiptera, but are instead closely related to the Palseodictyoptera. The order was obviously a widely dis- tributed one, members having been found in Permo-Car- boniferous strata of both Europe and North America; and specimens from Triassic rocks of Australia show that it persisted into the Mesozoic. The Triassic representa- tives, by the way, are remarkable in that the fore wings had a very large stridulatory area. The Palseozoic Proto- hemiptera had long cerci and well developed prothoracic wing lobes, like those of the Palseodictyoptera. The pres- ence of suctorial mouth-parts raises the question of feed- ing habits. It is obvious from their modified mouth-parts that the Protohemiptera consumed liquid foods ; whether this was plant juice, from such gymnosperms as lycopods, seed-ferns, and horse-tails, or the blood of reptiles and amphibians, is uncertain. But it is most interesting that as far back as the Upper Carboniferous, at least two hun- dred twenty-five million years ago, the suctorial mecha- nism had been developed in insects; and also that this device originated in relatives of the may-flies and dragon- flies, quite independent of its subsequent development in the Hemiptera and the Diptera.




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76 Psyche [June
The largest extinct order of Carboniferous and Per- mian times was the so-called Protorthoptera. This in-
cluded a bewildering variety of insects, suggestive of most of the orders to which we apply the term Orthop- teroidea. Some show definite traces of characteristics found in the cockroaches, others recall the mantodean and even the saltatorial Orthoptera ; but so far no satisfactory division of the Protorthoptera has been proposed. All of them were neopterous, i.e., folded their wings over the abdomen at rest. The more primitive types, however, possessed pronotal lobes, like those of the Palseodicty- Figure 3. Pro'bnis speciosa Sellards (Order Protorthoptera), from the Lower Permian of Kansas.
Original restoration, based upon specimens in the Museum of Comparative Zoology.
optera.
Their wings were unequal, the hind pair having' an expanded and plicate anal area.
In certain Permian
species, and perhaps also some Carboniferous ones, the fore wings were tegminous and distinctly punctate. A prominent ovipositor and cerci were present in most spe- cies. Apart from the wings, the prothorax showed the greatest amount of diversity. In many Carboniferous species, the prothorax was long and even armed with large spinous projections, whereas in others this segment was small and inconspicuous. The legs also showed much diversity. The fore legs of some were clearly raptorial,



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~arly~nsect Life
long and armed with spines and teeth; in. others they were curiotisly modified, perhaps for digging or cihbing (Fig- ure 3). The hind legs were specialized in some species for leaping, as in grasshoppers and crickets. It is appar- ent, therefore, that these early orthopteroids were a -vaned lot. They probably inhabited small seed-ferns, the phytophagous species feeding on the leaves and' the pre- , daceous ones on Palseodictyoptera and other .defenseless insects. They were not very large creatures, though a few attained a wing-expanse of six inches. The nymphs Bigure 4. paleuthygranvma te&omis Martynov (Order monearodea), from the Upper Permian of Russia. (After Martynov.) . of several families are known; they resembled the adulta closely and were obviously terrestrial.
Related to the Protorthoptera, but different enough to require ordinal separation, were the Caloneurodea, which ' existed during the Upper Carlioniferotas and Permian periods.
They were slender insects, with long antennae and ten-uate wings (Figure 4). The largest of them had a wing expanse of five inches. They differed from the Protorthoptera chiefly in having hind 'wings 'like the fore wings, with no enlargement of the anal area. In general
appearance the oalonenrodeans probably resembled the



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Psyche
[Tone
long-horned grasshoppers) except that their legs were cursorial, not modified for jumping. Their nymphs are unfenown.
The extinct orders which we have been considering have had a geologic record extending, throughont the Carbonif erons and Permian. We now come to two orders which are known only from the Permian period. One of these, the Protoperlaria, is the best town of all the ex- Figure 5. Protoperlarian nymph, from tile Lower Permian of Kansas. Original reBtoration, baaed upon specimens in the Museum of Cornpa-~ative qoology.
thct orders of insects, their remains being very abundant in Lower Permian rocks of Kansas and Oklahoma. The adults were similar to the existing stone-flies, but they , had pronotal lobes like the Palmdictyoptera, five tarsal segments, and a distinct, though small, ovipositor. The abdomen had long mrci and nine pairs of vestigal lateral gills, "recalling those of the PaIs~odictyoptera and some Megaseeoptera. That they were vestigial gills is shown by the nymphs (Figure 5). These were well adapted to



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Early Insect Life
an aquatic life, with swimming legs, and the lateral ab- dominal gills.
The other extinct Permian order, is the Protelytroptera, which includes the most highly modified of all the Paleo- zoic insects. They had true elytra, very thick and convex, though with vestiges of venation (Figure 6). The hind 'wings were large, with a greatly expanded anal region, and with hinges on the longitudinal veins enabling the å´win to fold up transversely as well as lengthwise. In Figure 6. Protelytrov, permå´henwn Tillyard (Order Protelytroptora), from the Lower Permian of Kansas.
Original restoration, based upon specimens in the Mrtseum oå Comparative Zoology,
general appearance these insects were highly suggestive of beetles, ht the venation of their hind wings shows clearlythat they were not at all allied to the Coleoptera. They might be related to the roaches or to the Dennap- tera; but most likely they represent an early and inde- pendent origin of the elytrophorons condition. Nothing is known yet of their monthparts or of their Immature stages.
The foregoing discussion, has dealt only with the extinct insect orders of the Upper Carboniferous and Permian periods.
Let us now turn to the living orders.
As we




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SO Psyche [June
noted earlier, although ten of these are known from Paleozoic rocks, only one has a record which goes back to the Upper Carboniferous-the Blattaria or cockroaches. Their oldest remains are found in early Westphalian strata, which were deposited about two hundred forty million years ago. These first specimens consist only of wings, but complete or nearly complete specimens have been found in late Westphalian and Stephanian rocks. It is clear from these fossils that even that early in the earth's history, the roaches were not very different from what they are now. They were flat, and had a broad pro- notum and tegminous wings like modern types. The venation, also, was similar to that which occurs in many of our living species-so much so that it is not easy to find obvious differences between Carboniferous and existing members of the gr'oup. Nymphal forms and several egg cases, which have been found in Permian rocks, serve to emphasize their similarity. Roaches are the most abundant of all Carboniferous insects. How- ever, this does not necessarily mean, as it has usually been interpreted, that they were the prevailing insects of the time; it merely means that they were numerous in a par- ticular region or environment. Most insect-bearing rocks were first deposited as mud, and the roaches presumably thrived in moist or damp regions having a luxuriant plant growth. The picture we get from the fossils can therefore be misleading, for it gives us a conception of the local biota only; if we had equally good samples of the fauna of dry regions, we would probably find the roaches less numerous. The size of the Paleozoic roaches has also been erroneously described. Although the statement is often made that giant roaches lived in the Carboniferous, no fossil specimens have been found which exceed the size of some of our living species. It is true, of course, that the average size of fossil roaches exceeds that of the exist- ing species; but that is because the large roaches had a better chance of being preserved as fossils than the small ones. This selective aspect of preservation is often over- looked.
Let us now consider the existing orders which first



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At any rate the maxillary and labial palpi were conapicn- ous and generalized in structure. Another interesting feature of the early paocida waa their wings. In existing species the hind pair are much smaller than the fore, with a redneed venation, but in the Lower Permian species the fore and hind wings were alike. Some of the Upper Per- mian members show the beginnings of hind wing reduc- tion. Presumably these small creatures had essentially the same habits as many modern, species, living under bark of trees or in leaf mould-but the trees and leaves were very different from those now inhabited by their descendants.
All the true bugs, i.e., Hemiptera, of the Permian were members of the suborder Hornoptera. Most of them were small, with a wing expanse of less than an inch, though in a few this reached two inches; The Lower Permian spe- cies were much less specialized than the Upper Permian , ones, but they had "the characteristic beak and maxillary and mandibular bristles of existing bugs. The wings are interesting because they were about equal in size, and because the hind wing had the venational features of



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Early Insect Life
psocid wings.
The best known of the Lower Permian
Hemipiera had a long, straight tube projecting from the end of the abdomen, but whether this was an ovipositor or respiratory tube remains to be determined. By Upper Permian time the Hornoptera had developed a variety of families, some of them approaching certain existing fami- lies (Figure 8). There can be no doubt, on the basis of their known structure, that these early bugs had already settled down to a diet of plant juices-
"We now come to the two remaining orders of insects which appear in the Lower Permian, the Mecoptera and Neuroptera. Their presence in Lower Permian rocks is Figure 8.
Pernocicada interga Beck. (Order HeiBiptera), from the Upper Permian of Russia. (After BetAer-Xigdisova.) interesting and surprising.
Since existing members of
both these orders have complete metamorphosis, we can conclude that the Permian species also had that type of development-unless, of course, we grant that complete metamorphosis might have arisen independently in the two orders, which seems improbable. True larval forms have been found in Permian deposits of Kansas, but their ordinal affinities have not been determined with certainty. The Lower Permian Mecoptera, or scorpion-flies, were very small, with a wing expanse of about an inch, though some of the later Permian species were more nearly the size of existing members of the order. Their body struc- ture was much like that of certain living genera, such as the Australian Chorista, the head including a short ros- tmm (Figure 9). During the late Permian, and, inci-



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84 Psyche [June
dentally, the early Mesozoic, the Mecoptera were rela- tively abundant and diverse: In onePermian deposit in Rnssia the Mecoptera make up 20% of the insect fauna found there, though at the present time they comprise less than .05% of the world's insect fauna. The Neuroptera of the Permian are no less interesting than the scorpion- flies. Two distinct types occur *Lower Permian rocks- the.Eaphidiodea or snake-flies, and the Planipemia. Very little is Imom of their body strnoture, but their winga indicate that, whereas the Lower Permian snake-flies were primitive and closely related to existing families, the -
(Figure 9. Agetochwwta tWyarSi Martyttov (Order Mecopbra), from tka pper Permian of RuBaia.
(After Martynw.)
Planipemlia were highly specialized, and only remotely .
related to existing groups. In Upper Permian rocks, however, the PIanipenGa are represented by an extensive series of fossils which are close to-certain living families, snch as the Berothidse? Sisyrida, etc.
There remain to be, considered now three other orders, two of which, the Thysanoptera and Perlaria, appear first in Middle Permian rocks, and the third, Odeoptera, in late Pedan deposits. The earliest Perlaria have been found in .Russian strata and altho-agh they are very frag-



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19471 ~arly Insect Life 85
mentary, their identification is substantiated by the pres- ence of more definite specimens in late Permian rocks of Australia. The latter were considered by Tillyard as being very closely related to the existing Eustheniidse of the Australian region. The Thysanoptera or thrips, also found in Russian deposits, are of course minute and the details of the wings are not known; but the fossils certainly show the general characteristics of the thrips. The first unquestionable Coleoptera, or beetles, are found in the Upper Permian of Russia and Australia. Un- fortunately, complete specimens are unknown, though sev- eral well preserved elytra have been found. The family relationships of the fossils cannot be ascertained on these structures alone; but several types of elytra are repre- sented, including some which are alike those of the Cu- pedidae, and others which recall those of the Hydrophilidse. It should be noted that since beetles are very abundant in Triassic deposits, their presence in the Permian is not surprising.
This then, is a general picture of early insect life. Our
knowledge of it is limited, and there are many gaps to be filled, but we do have some idea of its nature. In reality, two faunas existed during the geologic periods consid- ered-a Carboniferous fauna and a Permian one. The contrast between these two is fully as great as that be- tween the faunas of the Triassic and the present. Even by late Permian time, about one-third of all the living orders of insects had come into existence, and the abrupt appearance of so many existing orders in the Lower Per- mian suggests that some of them lived in Carboniferous time, though not yet found in strata of that period. This early insect fauna included both predators and plant feeders, some of which had suctorial mouth-parts. The metamorphosis of the Carboniferous species, so far as known, was of the incomplete type, some apparently having aquatic nymphs ; but by early Permian time, com- plete metamorphosis had been acquired. All of this took place before the existence of flowers or mammals or birds-to say nothing of man. It is no wonder that the insects have such a tenacious hold on what we consider to be our planet.




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