24 



THE PRINCIPAL NATURAL ENEMIES OF THE SPRUrE-DESTROVlNC?^ 



BEETLE. 



Among a luiiiilx^r f)f insect enemies of the different stages of tlie 

 beetle at least two are worthy of special mention — one a true parasite, 

 the other a predaceous enemy. 



A PARASITIC INSECT. 



The commonest parasite of the larva? is a small fonr-winged wasp- 

 like insect belonging to the order Hymenoptera, family Braconidfe, 

 genus Braeon, and species swijjlex Cress. This insect appears on the 

 wing about the time or a little before the beetles emerge from the bark 

 in the earlj^ summer and commences to deposit its eggs b^' means of a 

 long, stinglike ovipositor Avhich it inserts in and through the bark 

 infested bj' different stages of the larvae, on or by Avhich it places its 

 eggs. The minute maggot hatching from this egg attaches itself to 

 thc/^side of its victim and sucks out and feeds upon the liquids of its 

 body. The beetle larva soon dies, and after the parasite larva has 

 attained its full growth as such it incases itself in a thin, paperlike 

 cocoon (PI. VII) in which it goes through its transformation to the 

 adult. It then emerges and in a like manner continues its good work 

 in destroying the destroyer. While cocoons of this parasite were f re- 

 ({uently met with in the larval mines of the l)eetle in nearlj' every 

 locality where infested trees were examined, it was nowhere com.mon 

 enough to be of any special service except neai' the sources of the 

 Kennebago and Dead rivers. Here it was quite common and had 

 killed a great many larva?. In one tree as many as six cocoons were 

 found in a jjiece of bark 2 inches square. It is only in the thinnest 

 bark, however, that this parasite can do much good in destroying the 

 larva*, and since the beetles usually select only the old trees with thick 

 bark, and do not infest the tops where the bark is thinner, it would 

 appear that this parasite can not, alone, do a great amount of good. 

 In connection with other beneficial factors, however, it contributes its 

 share to reducing the numbers of the destructive beetles, and thus is 

 an important factor. 



A PREDACEOUS BEETLE, 



Different stages of a beetle closely related to the one that was intro- 

 duced by the writer into the spruce and pine forests of West Virginia 

 from Germany in 18'.)2-93, to prey upon the destructive pine bark 

 beetles, were frequentlj^ met with wlien examining infested trees, but 

 were not especially common, except in the same section where the par- 

 asite was common. 



This beetle belongs to the order Coleoptera, familj' Clerida?, genus 

 Thanasimus, and species iiiihiJus. It is antlike in appearance, espe- 

 cially when luiiiiingaboutonthe bark. The adult is about one-fourth 



