SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 85, NUMBER 7 EFFECTIVENESS IN NATURE OF THE SO-CALLED PROTECTIVE ADAPTATIONS IN THE ANIMAL KINGDOM, CHIEFLY AS ILLUSTRATED BY THE FOOD HABITS OF NEARCTIC BIRDS BY W. L. McATEE Bureau of Biological Survey U. S. Department of Agriculture (PUBLICATION! 3125) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION MARCH 15, 1932 Z-tfc JSorb (§a(timoxc {pveoe BAI.TIJIUKl;;, MD., U. ,S. A. Smithsonian Miscellaneous Collections Vol. 85, No. 7 EFFFXTIVENESS IN NATURE OF THE SO-CALLED PROTECTIVE ADAPTATIONS IN THE ANIMAL KINGDOM. CHIEFLY AS ILLUSTRATED BY THE FOOD HABITS OF NEARCTIC BIRDS By W. L. McATEE ERRATA Page 56. In the table Identifications of Lepidoptera, the middle column is a relic from a set of calculations of the percentages of identifications among all insects. The appended figures are to be substituted as represent- ing the percentages of identifications among all Lepidoptera. In explanation of the third column in this table, it may be said that it differs from others given further on in the work by omission of figures for families not represented among the food identifications. Percentage of identifications anionf! all Lepidoptera 2.6992 .0270 .0270 .8060 .0919 •2055 .0108 .0270 .0108 .0108 .4706 .0324 .9412 .0378 •6383 6.IOI5 .0216 .3678 •3570 .15' '8 .8438 1 1 .4458 .0487 .0054 •3191 .0054 .0108 .2218 .61 [J .7248 68.5670 1.2279 3-5:^76 entry for the family Diopsidae Page 86. The figure i before the decimal in the should be deleted. " " " " the heading Pages 102-105. Insert the word aquatic after the word all in for the middle column on each of these pages, with the exception of that at the bottom of page 105. EFFECTIVENESS IN NATURE OF THE SO-CALLED PROTECTIVE ADAPTATIONS IN THE ANIMAL KINGDOM, CHIEFLY AS ILLUSTRATED BY THE FOOD FIABITS OF NEARCTIC BIRDS By W. L. McATEE bureau of biological survey, u. s. department of agricultukk CONTENTS p^^^^ Introduction 2 Protective adaptations 4 Animals eaten by Nearctic birds 6 Data cited and how obtained 6 Identifications of animal food 8 Protozoa (one-celled animals) 9 Porifera (sponges) 10 Coelenterata (hydras, jellyfishes, sea-anemones) 11 Platyhelminthes (flatworms, flukes) 13 Nemathelminthes (threadworms, roundworms) 13 Trochelmintlies (rotifers) 13 Molluscoida (corallines, lampshells) 13 Echinodermata (sea-cucumbers, sea urcliins, starfishes) 14 Annulata (worms) 15 Arthropoda (jointed animals) 16 Crustacea (crabs, shrimps, sowbugs) 17 Myriapoda (thousandlegs, centipedes) 22 Insecta (insects) 24 Aptera f wingless insects) 27 Odonata (dragonflies, damselflies) 28 Agnatha (mayflies) 20 Plecoptera (stoneflies) 30 Isoptera (termites) 31 Orthopteroidea (embracing the following 5 groups) ,^2 Dermaptera (earwigs) ;^j Cheleutoptera (walkingsticks) 33 Saltatoria (grasshoppers, locusts, crickets) 3 I Paleoptera (roaches) 38 Dictyoptera (mantids) 3;) Corrodentia (psocids) 39 Mallophaga (biting lice ) 40 Siphonaptera (fleas) 40 Thysanoptera (thrips) 40 Rhynchota (bugs, cicadas, leafhoppers, scale insects) 41 Neuropteroidea (dobsonflies, snakeflies, scorpionflies, ant- lions, caddisflies) 49 Lcpidoptera (mciths, butterflies) 52 Smithsonian Miscellaneous Collections, Vol. 85, No. 7. I 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 PAGE Coleoptera (beetles) 63 Mecaptera (scorpionflies) 84 Diptera (flies ) 84 Hymenoptera (ants, bees, wasps) 88 Arachnida (scorpions, spiders, ticks, etc.) 97 Mollusca (snails, slugs, mussels, limpets) loi Chordata (lancelets, tunicates, vertebrates) no Pisces (fishes ) 112 Amphibia (salamanders, toads, frogs ) 120 Reptilia (turtles, lizards, snakes) 123 Aves (birds) 126 Mammalia (mammals) 131 Discussion I35 Indiscriminancy of predators other than birds 136 More theoretical aspects of indiscriminancy by predators 140 Indiscriminancy of normal checks other than predators 141 Relative importance of natural checks 141 Summary I43 Bibliography MS INTRODUCTION In a previous paper ^ the writer set forth reasons for beheving that the results of experimental tests of the effectiveness of the so- called protective adaptations in protecting animals from their enemies are not trustworthy indications of what occurs under natural condi- tions. In the present contribution he proposes to show just what insects and other animals are actually preyed upon by wild birds of the United States, Canada, and Alaska, giving also incidental notes on other enemies. This evidence reflecting food habits under natural conditions goes far to show how little the alleged protective devices have to do with choice of food by vertebrates. Judging from the literature of the subject since 1912, the con- tentions of the article on the experimental study of the food habits of animals seem to have been generally admitted, or at least regarded as too well supported to be lightly attacked. Only one essay has been seen l)y the writer, that seems in any way a reply, namely an account of " Experiments and Observations Bearing on the Explanation of Form and Colouring," "" by C. F. M. Swynnerton, who refers to my criticism of the experimental method as " rather over-vigorous." The vigor of the criticism is admitted l)ut in view of the absurdity of the arguments against which it was directed, it can hardly be considered 'The experimental method of testing the efficiency of warning and cryptic coloration in protecting animals from their enemies. Proc. Acad. Nat. Sci. Philadelphia, June 1912, pp. 281-364 (Sept. 6, 1912). * Journ. Linn. See, Zool., vol. 33, pp. 203-385, London, June 30, 1919. NO. 7 PROTECTIVE ADAPTATIONS McATEE 3 excessive. Undeniably selectionists have lieen absurd in their ch's- " " quisitions on adaptations ; for instance eye-spots on a butterfly's wings are to direct the attack of enemies to a nonvital spot, while "eye-spots" on a caterpillar are "terrifying" and prevent even a touch where merely a touch would be fatal ; in numerous species of birds the male is colored red and black or orange and black, characteristics that selectionists say have been developed by sexual selection as an attraction to the opposite sex, yet the females of these birds are supposed to be repelled by the same colors in possible insect prey ; red insects are said to be warningly, red fruits invitingly colored, and so on. A popular foible of similar type is that of sports- men who hold up to admiration the marvelous protective coloration of game birds, and in the next breath complain of severe depredations on these birds by " vermin." But this is digressing and the writer is glad to acknowledge that if all of the experimenters had been as critical of their methods and conclusions as Mr. Sw^ynnerton, the tone of his former paper would have been quite dififerent. For instance Mr. Swynnerton carried on more experiments than any of the authors reviewed in the previous communication, before he, according to his own confession, learned how to experiment. This in itself confirms the writer's charges that the experiments he reviewed were both inadequate and misinterpreted. It may further be stated that the principal conclusions Mr. Swynner- ton draws from his experiments and observations would have been agreed to in advance by anyone experienced in the study of bird food. Thus he concludes that birds show preferences among the food items available to them, and that predatory animals of various groups show more or less agreement in preferences. From his general experience with birds he decides also that " Unless through sheer impossible hardness, size, etc., there is practically no such thing as ' inedibility,' and he appreciates that a group of insects, limited in numbers as are butterflies, will not be taken by insectivorous birds out of proportion to their abundance as compared to all insects available. These things did not require experimental test for they are cor- roborated in every thorough report on the natural feeding habits of birds. What can not l)e admitted, however, is that preferences of birds learned by feeding them upon some certain group of insects to an extent far greater than the birds ever prey upon them in nature, reflect normal feeding habits, nor that there is evidence of intensive enough feeding by discriminating enemies upon any group of insects 'A brief preliminary statement of a few of the results of five years' special testing of the theories of mimiery. Proc. Ent. Soc. Lond., 1915, pp. xxxii-xliii. ; 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 to meet the requirements of the selection theories. We further can not admit what the experimenters imply, namely, that the analyses of the stomach contents of birds fail to reveal the approximate num- bers present of certain insects (such as butterflies) which they believe are eaten to a considerable extent. This point will be discussed later. So much for what has happened between the previous paper and the present, which as stated, will be devoted chiefly to an exposition of the animal food of nearctic birds, with special reference to the so-called protective adaptations. PROTECTIVE ADAPTATIONS The characteristics of animals that are usually classed as protective adaptations include resemblance to generalities or details of the en- vironment, whether through color or other modification of the animal itself or utilization by it of materials from the environment for concealment, the possession of protective bristles, spines, hard in- teguments, stings, poisonous bites, and the like, and nauseous or irritating odors or tastes. There are animals with actually poisonous properties among many of