LAEV^ OF THE PEIONINJE. 5 



dry wood, and many under the bark of recently dead or dying trees, 

 either completing their larval growth between the bark and wood, 

 or going into the sapwood, deep into the heartwood, or into the 

 outer bark to pupate. 



Even the frass or borings of these larvae are usually character- 

 istic, the latter on account of the peculiar shape of the mandible. 

 Thus a mandible with gougelike cutting edge produces broader 

 chips, while the acute mandible cuts a narrower shredded chip. 

 The galleries are either packed with tight, fine frass, filled with fibrous 

 chips, or left open. 



Certain groups or species will excavate their emergence holes 

 through the exterior before pupation, suggesting that the imagines 

 had emerged; but in most cases this is left for the adult. 



A few species construct their mines in the outer corky bark of 

 livmg trees; others in the inner bark and cambium, sapwood, or 

 heartwood of living and dead trees; others girdle living twigs and 

 either live in the girdled portion or work downward into the living 

 branches. 



It is remarkable to what extent the exact conditions of decay and 

 moisture will limit the activities of certain species. For example, in 

 a long vine of bittersweet {Celastrus scandens) from which as many as 

 five to six species have been reared, that portion of the vine near 

 the ground, more moist and decomposed, will hold exclusively one 

 or two species; higher up in drier wood there will be another; and 

 if the branch merges into hving wood here, still another. Even in 

 these local limits some will mine the pith, others the wood, and 

 others the bark. 



Closely correlated with their biology is the form of the larvae. 

 Bark-boring species are more or less flattened, and if the final stages 

 are passed in the same environment, the adult will often be more or 

 less flattened. If they go into the wood, the larvae attain a more 

 cylindric form. Those boring in the pith of stems nearly always 

 have a very cylindric form, as have the adults. If they work in living 

 tissue, especially when all the species of a genus have the same habit, 

 the larvae are, with scarcely an exception, armed with chitinous 

 asperities on the thorax and ampullae. In general the form and size 

 of matured living larvae is a good criterion of that of the adult, but 

 when preserved for study the expansion or contraction renders the 

 length unreliable. For this reason size is not given much importance 

 in this paper. If an adult is large it necessarily foUows that the 

 matured larva is likewise. Matured larvae are always well filled, the 

 intersegmental skin expanded and usually of a whiter color, becoming 

 more contracted in the prepupal stage and the integument wrinkled 

 before pupation. 



