PROTECTIVE COLORATION IN 



SEEDS OF BOLIVIAN MAIZE 



Each Seed Ordinarily Infested by Not More than One Larva -Mottled Seeds 



Look as if They Had Already Been Entered, and Therefore 



the Larvae Appear to Discriminate against Them 



J. H. Kemptox 

 Bureau of Plant Industry, Washington, D. C. 



PROTECTIVE color.ation in ani- 

 mals is familiar, but in plants it 

 is not so common. What may 

 be a case of protective markinjij 

 has been found recently in a shipment 

 of maize from Bolivia. 



In a collection of maize secured from 

 the Bolivian exhibit at San Francisco 

 in 1915, through the courtesy of Dr. 

 Otto Buchtien, an ear was found with 

 kernels that had the color of the aleurone 

 cells distributed in a curious mottled 

 pattern strongly suggesting the api^ear- 

 ance of self-colored seeds that had been 

 infested with the larvae of the Angou- 

 mois grain moth {Siiotroga cerealella). 



The possibility of this resemblance 

 serving as a protection against the 

 Angoumois moth was immediately sug- 

 gested. Several investigators have 

 recognized that two larvae do not enter 

 a kernel of wheat or other small grains, 

 but so far as known this fact has not 

 been established for maize. The fact 

 that a single larva com])letely consumes 

 the contents of one of these small 

 grains may account for the fact that 

 they usually sujjport but one larva. 

 A seed of maize, hcjwever, is large 

 enough to ]jrovide ample food for two or 

 more, and unless some selection is 

 exercised by the larva many seeds 

 should be found hax'ing more than one 

 occupant. 



As the eggs of the Angoumois molh 

 are laid in batches of about thirty, the 

 discrimination in the choice of seeds 

 must be made by the larvae. 



If selection is exercised it does not 

 seem unreasonable to supjiose that the 

 track in the aleurone layer serves as a 

 warning to the newly hatched larva 

 that the kernel already hasaninhabitant, 



200 



and it seems possible that the mottled 

 seed sufficiently resembles the track of a 

 larva to accomplish the same result. 



The mottled ear was shelled and the 

 niunber of infested seeds determined. 

 There were 202 undamaged seeds and 

 100 with a single larva, but none was 

 found with more than one larva. 



As further e\'idencc that larvae avoid 

 seeds already occu])iecl, a census of the 

 self-colored ears from the same collec- 

 tion is shown in Table I. If the selec- 

 tion exercised by the newly hatched 

 larvae were perfect no seeds having 

 more than one inhabitant should be 

 found, while the table shows many such 

 seeds. The nuinber, however, is far 

 short of that which might be exj^ected 

 had there been no selection. Some 

 degree of selection, then, would seem to 

 be a fact, and newly hatched larvae do 

 avoid seeds already inhabited. 



If it is admitted that the white 

 tracks left by larvae deter other larvae 

 from entering the seed, it does not ap- 

 pear too fanciful to suppose that the 

 white mottling which so closely re- 

 sembles the tracks, serve the same pur- 

 ])ose. The idea is strengthened by 

 the small percentage of infested seeds 

 and the fact that none was found having 

 two inhal)itants. It is, of course, pos- 

 sible that the mottled ear was more 

 favorably situated and hence was not 

 subjected to the same severe attacks. 

 This chance, however, is remote as the 

 remaining ears of many tyj^es that 

 occupied the same case were all badly 

 infested. 



A compari.son of the degree of double 

 infestation on a self-colored ear having 

 all the seeds infested, with the degree 



