73 



not uncommon, and generally fly near the ground, but their habits are otherwise 

 unknown. I have taken them as far eastward as Nova Scotia, but I do not know 

 how far westward their range extends. The male is exceedingly rare, and I have 

 only seen one specimen that was captured in Ontario. 



Although this review of the great complex of insects embraced in the Para- 

 sitica has been a very rapid and incomplete one, I hope that it has at least given 

 some idea of their great number, their diversity of structure and their economic 

 importance. We see that egg, larva and pupa are alike subject to their attacks, and 

 that scarcely any form of insect defence appears to be sufficient to prevent their 

 attacks. The grub gnawing his hidden burrow in the tree, and the scale insect 

 adhering firmly to the twig, alike have their parasitic foes differing in size and 

 method of attack. 



It will be observed further that the value of any species in destroying 

 obnoxious forms does not depend upon its size or strength. The greatest benefits 

 are often effected by atoms so minute as almost to escape our search, but which 

 by their numbers work wholesale destruction to their victims. The tiny fly that 

 destroys a cluster of* eggs is a greater helper than the larger one that might later 

 destroy the brood of caterpillars, because in the latter case a certain amount of 

 depredation is committed before the labours of the parasite are fulfilled. The 

 diminutive devourers of aphides arp of unknown value, as plant-lice increase so 

 enormously by rapidly succeeding generations that if it were not for such pro- 

 vidential safeguards they would swarm everywhere working devastation. 



INSECTS I^^JURIOUS TO THE ELM. 



BY F. B. CAULFIELD, MONTREAL. 



First are insects injurious to the trunk. 



1. The Common Elm-tree Borer, Saperda tridentata, Oliv, Order Coleop- 

 tera, Family CerambycidjB. — A very destructive insect, boring in the inner bark 

 and the surface of the wood of elm trees. Fitch states that the eggs are deposited 

 in June and that the young larvae nearly complete their growth before winter, 

 and soon after warm weather arrives in spring they pass into the pupa state. 

 Packard, who has found the larva in abundance in spring in Providence, under 

 the bark of old dead elms, describes it as lollows : — " White, sub-cylindrical, a 

 little flattened, with the lateral fold of the body rather prominent ; end of the 

 body flattened, obtuse, and nearly as wide at the end as at the first abdominal 

 ring. The head is one-half as wide as the first prothoracic ring, being rather 

 large. The prothoracic segment, or that next to the head, is transversely oblong, 

 being about twice as broad as long ; there is a pale dorsal corneous transversely 

 oblong shield, being about two-thirds as long as wide, and nearly as long as the 

 four succeeding segments ; this is smooth, except on the posterior half, which is 

 rough, with the front edge irregular and not extending far down the sides. Fine 

 hairs arise from the front edge and sides of the plate, and similar hairs are 

 scattered over the body and especially around the end. On the upper side of 

 each segment is a transversely oblong ovate roughened area, with the front edge 

 shghtly convex, and behind slightly arcuate. On the under side of each segment 

 are similar rough horny plates, but arcuate in front, with the hinder edge 

 straight. 



