March, 1905] Powell : Wings of Certain Beetles. 21 



Fig. 32. T. plastographus. Full grown larva ; side view. 



Fig. 33. Dendroctonus valens. Larva ; side view. 



Fig. 36. Dendroctonus valens. Cross-section of wing disc, showing an early 

 stage of the evagination. 



Figs. 34, 35 and 37. Tomicus plastographus. Early stages in the evagination 

 of the wing. 



Fig. 38. T. plastographus. Cross-section of wing bud showing thread-like 

 bases of the cells and a trachea pushing into the wing. From larva at about the be- 

 ginning of the prepupal period. 



LITERATURE CITED. 

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Ent. Soc, v. 20, p. 162. 

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(1891.) Beitrage zur Vergleichenden Embryologie der Insecten. Der 



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etc. Psyche, pp. 246-250. 

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 24, pp. 783-797. 

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 Miall & Hammond. (1900.) The Harlequin Fly. Oxford. 



Muller. (1875.) Beitrage zur Kentness dei Termiten. Jenaische Zeit. fur Natur- 

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