ENGRAVER BEETLES. 



Scolytus rugulosus (Plate LXXXVI), the Fruit-tree 

 Bark-beetle, is typical of the Scolytinae. The numerous 

 small "worm-holes," which make the outside of the bark 

 look as if it had received a load of shot, are formed by the 

 adults in boring out. Each female then burrows in at a 

 new place and eats a vertical tunnel partly in the bark and 

 partly in the sap-wood. Along the sides of this tunnel 

 she makes small pockets and puts an egg in each. The 

 young larvae tunnel at right angles to the "broad burrow" 

 and each pupates at the end of its own burrow. When the 

 adults emerge from these pupae, they bore straight out 

 and so give the tree the "shot" appearance. If the insects 

 are very numerous, their galleries girdle the tree and it 

 dies, although it happens that this particular species 

 usually works in trees that are dying from some other 

 cause. 5. 4-spinosus terribly damages the hickory trees 

 near New York and its "bird-shot" emergence holes are a 

 common sight. 



The subfamily Ipinae contains most of our species. 

 Their food-habits are various but they usually live in 

 trees, some in the solid wood instead of just beneath the 

 bark. It should be said that many, especially those living 

 in diseased wood, seem to feed more on the fungus ("am- 

 brosia") which grows in their galleries than they do on the 

 wood. Probably emerging females carry, but not inten- 

 tionally, the spores of these fungi when they leave their 

 childhood homes to start new establishments. 



STREPSIPTERA 



These curious creatures are put in a separate order, as 

 here, by some good authorities, while others class them as a 

 family, Stylopidae, of heteromerous beetles. They are all 

 parasitic upon other insects. The females are wingless 

 and Plate LXXXV shows one sticking out of the abdomen 

 of a wasp. The same plate shows a typical winged male, 

 greatly enlarged. 



405 



