MONOGRAPH OF THE GENUS SAPERDA I7 



Grouping and summary of the food habits of the larvae 



The larvae of this genus may be divided by their food habits into 

 three classes : ( i ) those that bore in the large branches and trunks 

 of living trees and feed on the sap, calcarata, Candida, cre- 

 tata, vestita and possibly hornii and mutica; (2) those 

 that live in small branches and usually produce galls, subsisting on 

 sap, and not making the extended galleries of the first group, f a y i , 

 populnea, obliqua, concolor; (3) those that feed on liv- 

 ing and dead tissues of dying or recently killed trees, tridentata, 

 discoidea, lateralis, imitans and puncticollis. 

 The manner of feeding and the portion of the tree attacked vary with 

 different species, and most of the forms have special food plants. 



S. obliqua feeds close to the ground at the collar of the black 

 alder, where it often entirely girdles the stem, forming a knot or gall 

 and ultimately killing it; and, when not entirely girdled, the tree is 

 so weakened that the stem soon breaks. A walk through an alder 

 swamp where this insect is common will show a great number of 

 prostrate stems in all stages of decay. 



S. mutica. This species is said to live on the willow and is the 

 only eastern form that we have not bred and of which we have been 

 unable to secure workings. 



S. hornii feeds on the willow according to Dr H. C. Van Dyke, 

 who has taken the insect on that plant. 



S. Candida is usually very com.mon in apple and attacks sev- 

 eral allied trees. It is quite destructive to seedlings and young 

 trees, where it works at the base of the trunk and roots, and, as sev- 

 eral generations follow in the same wound, the tree is soon killed. 



S. calcarata works in the trunk and larger branches of the 

 silver poplar in particular and soon kills the trees. It is surprising 

 to see the quantity of sawdust around a badly infested tree, thrown 

 out by the larvae when making their pupal chambers. 



S. tridentata works in and under the bark of the trunk and 

 branches of the elm, and has also been recorded in other trees. 



S. cretata lives in the thorn and apple, usually in the trunk and 

 larger branches, and works somewhat like S. calcarata, but the 

 burrow is longer and more tortuous. 



