i3 6 ENTOMOLOGICAL NEWS. [March, '08 



The Abnormal Appearance of External Wing-buds 

 in Larvae of Holometabolous Insects. 



BY WM. A. RILEY, Ithaca, N. Y. 



The literature of entomology abounds in reported instances 

 of insectan malformations varying- all the way from slight 

 abnormalities in venation or in the segments of an antenna, to 

 duplication of appendages, or to those striking monstrosities in 

 which the head of the larva is preserved by the imago. When 

 we consider the minute scrutiny of the systematists it is not 

 surprising that the vast majority of these instances relate to 

 adult insects. It is to another type of abnormality the appear- 

 ance of external wing-buds in the larval stage that I wish to 

 call attention. 



It is a well known fact that the wings of insects with com- 

 plete metamorphosis are developed as internal invaginations 

 during the larval stage and normally become visible externally 

 only at the time of pupation. So far as I know the recorded 

 cases of abnormalities in which the wing-pads are external in 

 the larva all relate to two species of Coleoptera. Tenebrio 

 molitor and Anthrenus varius.* To these may now be added 

 a third, that of the Pyrochroid, Dendroides canadensis Latr. 



In 1896, while experimenting with meal-worms (Tenebrio 

 molitor}, Heymonsf found a full-grown larva which possessed 

 a pair of peculiar appendages on the meso- and metathorax. 

 These appendages were symmetrical, those on the mesothorax 

 being somewhat larger than those on the metathorax. Closer 



*I except the remarkable cases, reported by Cesare Majoli, 1813, 

 of silk worm larvae which, instead of forming cocoons after the fourth 

 molt, developed wings and other structures of the adult. From the 

 meager accounts available (Stannius '35, Hagen '72) it seems to me 

 that we here have to do rather with abnormal adults which have pre- 

 served larval characteristics. To be sure, the line between the two 

 types is rather arbitrary and it is greatly to be hoped that in the fu- 

 ture any instances similar to those recorded by Majoli will be carefully 

 and fully reported. 



t Heymons, R. '96. Flugelbildung bei der Larve von Tenebrio 

 molitor. SB. Ges. naturf., Berlin, 1896, pp. 142-144. Also in Ent. 

 Rec. xi, pp. 67-68. 



