THE GENUS DENDROCTONUS. 



143 



lives in the middle of pockets full of resin. During the larval period micans conducts 

 itself differently from other Belgian hylesinids in that each larva does not make a 

 separate gallery, but all work together, making one common wide gallery. The egg- 

 laying extends sometimes over several months. This results in a parallel develop- 

 ment of larvae, pupae, and adults, which are to be found thus during the greater part 

 of the year. 



The excavation of the gallery begins the last of May or the first of June. 



The attack of the insect, which traverses the bark to reach the sap wood, causes each 

 time an abundant flowing of resin mixed with sawdust and excrement, which gives 

 it a brownish color, sometimes violaceous. This resin often forms nipplelike blocks, 

 sometimes 30 mm. high by 25 mm. in diameter, which dry and harden in the air and 

 finish by crumbling. The particles fall at the foot of the tree, among the needles 



A B 



Fig. 93.— The European spruce beetle. Egg galleries and larval chamber: A, Basal sections of egg 

 galleries; B, advanced stage of work; a, entrance burrow; b, excavated July 8-16; c, excavated 

 July 8-29; d, eight days old; e, three weeks old; /, basal section; g, boring dust; h, subsequent or 

 inner gallery ("mother gallery"); j, egg nest with eggs scattered about in boring dust; k, social 

 chamber excavated by larvae; I, boring dust and resin; m, larvae at work. (Adapted from Pauly, 

 Forstlich-naturwissenschaftliche Zeitschrift, I Jahrgang, figs. 3 and 4.) 



forming the ground cover, often being in a very considerable number, resembling the 

 dried lumps of mortar at the foot of a freshly constructed wall, following the excellent 

 comparison of Altum. 



The egg gallery is vertical, frequently curved and somewhat irregular, sometimes 

 doubly inflected, having 12 to 20 cm. of length. The female here deposits from 20 to 

 25 eggs several times. Following this she quits this place, to commence upon another 

 point of the same tree or upon neighboring trees, even to the deposition of from 150 

 to 200 eggs. Sometimes she is found dead in a final gallery having deposited but a 

 few eggs, the rest of her provision. 



The egg laying is done slowly after this preparatory work. It is therefore easily 

 understood that a female which has deposited her first eggs about the month of June 



