542 PHYSIOLOGY. 



damicornis, Lamia tribulus, &c., which live in the stems of Brazilian 

 or tropical plants, particularly those of the genus Bombax. 



The stems of corn also serve as a dwelling-place for many larvae ; 

 thus we find the maggot of a fly belonging to the genus Mosillus, of 

 Latreille, subsisting in the blade of wheat. Another, known by the 

 name of the Hessian fly, also lays its eggs in the blade of wheat, and 

 thus frequently destroys entire fields, from the increasing maggot 

 devouring all the leaves. Musca pumilionis, Lin., lays its eggs in the 

 heart of young rye, and the larva destroys the shoot, commencing with 

 the germen and then consuming the leaf. Pyralis sicalis attacks in a 

 similar manner the blade of barley, depositing its eggs in a cavity bored 

 between the leaf and stem. Exotic grasses also are destroyed by 

 enemies which consume their pith. An ant (Formica analis, Latr.) 

 makes its dwelling in the interior of the sugar-cane, and feeds upon its 

 sweet pith ; another (F. xaccharivora, Lin.), takes up its abode 

 between the cellular roots of the same plant, and thus destroys it by 

 drying it up. In the fortieth year of the preceding century this ant 

 had so much increased in the island of Granada that every plantation 

 was destroyed by it, and every means applied to remove the evil was 

 fruitless. The larvae also of the Elatcr noctilucus, of which we have 

 already spoken, lives in the pith of the sugar-cane, and feeds upon it *. 



The larvae of many Lepidoptera live in the interior of the stems 

 and of the twigs, or beneath the bark, and thereby prevent the growth 

 of the plant : thus, for instance, we find the caterpillars of several 

 moths, as that of Tinea corticella, Fab., beneath the bark of trees ; 

 and another caterpillar, that of Tortrix Weberana, F., is the cause of 

 great injury to fruit trees, by boring through their bark. The cater- 

 pillar of Thyris fenesirina , O., lives in the annual twigs of the com- 

 mon Sambucus niger, L., and of Arctium lappa, and destroy their soft 

 pith. But the caterpillars of the genus fiesta are well known as 

 borers of the stems of trees, but from their small number we have never 

 heard of extraordinary devastations committed by them. Thus the 

 caterpillar of Sesia apiformis lives in the stems of all kinds of poplars, 

 as does that of S. asiliformis in the young stems of Populus dilatcita, 

 L. ; .5?. spheciformis in the stems of the elders and birch trees ; S. 

 hylesifbrmis in the branches of Rubus Idteus, L. ; S. cidiciformis in the 

 bark of plum and apple trees; S. formica; formix in the branches of 



* Hutnboldt, Essai sur la Geographic ties Plantes, p. 136. 



