48 THE REPORT OF THE No. 36 



are all parasitic in the larval stage, their hosts being usually bees, occasionally 

 wasps and (in the case of Epicauta) locusts. The norma! form of the larva is 

 preceded by a very active louse-like insect known as a triungulin (each leg termin- 

 ating in a triple set of hooks). The larva that suijceeds the triungulin is inactive 

 and almost legless ; moreover, in some cases the true pupa is preceded by a sort of 

 preliminary pupal form from which emerges a larva of habit almost as active as 

 the original triungulin, though it does not feed. 



The triungulin is a monomaniac; I mean a creature of but one idea, one 

 single goal of ambition, and its six active legs enable it to get there. The loadstone 

 that draws the triungulin like a steel-filing to a magnet is the egg of its host. In 

 the case of Epicauta vittata this is the egg cluster of a locust, and the parent beetle 

 takes the precaution of laying its eggs near where the locust has hidden its egg- 

 batches in the ground. Among the Cantharids whose host is a genus of bee 

 (Anthophora), the beetle oviposits near the bees' nest, but in order that the tri- 

 ungulin may reach the egg of the bee, it has to be carried into the nest by a queen 

 bee; its instinct impels it to seize the first hairy object within reach. This frequently 

 proves to be the leg of a drone and in some cases the triungulin manages to transfer 

 itself to the leg of a queen bee during the nuptial flight and so reaches its goal, 

 the egg-cell in the hive. But hundreds of triungulins must perish from seizing 

 a wrong object, and in order to compensate for this, selection has enormously 

 increased tlio fertility of the female beetle, which lays as many as 2,000 eggs. 

 In the Meloe or Oil-beetle the instinct is even more imperfect; the beetle does not 

 lay her eggs near the home of the host and the triungulin mounts to the top of 

 grass stems or enters a blossom and waits there for a hair (any hair will do) ; this 

 more often than not proves to be growing on the leg of a fly, or if a bee, the wrong 

 kind, and thousands of the triungulins, instinctively seizing the first hairy object 

 that offers, are carried into space to perish miserably. All that saves the Meloe 

 from utter extinction is the stupendous fecundity of the female, the clutch of egg?' 

 laid ^y this Apteryx among insects producing a brood of no fewer than 10,000 

 triungulin chicks. 



Apart from the great Phytophagous group of beetles, easily the best known 

 family of leaf-eaters is the Scarabgeids. One section of this family consists of 

 scavengers pure and simple, the larva being nourished in manure or rotting wood, 

 and the female laying her eggs in such material. But an important branch of 

 the family is phytophagous, the larvse feeding on living vegetable matter, usually 

 the roots of grasses and herbaceous plants, and the mature insects often feeding 

 voraciously on leaves of trees or soft vegetable tissue. 



In this family of beetles, structurally so different from the Phytophagous 

 Beetles, strictly so called, it is interesting to note how far one group has diverged 

 from another in response to conditions entailed by their chosen food ma^terial. 

 Among the Coprini you find the larval stage completed in a few weeks or at most 

 months, while the life of the mature beetle (as in Scarabaeus) extends over a period 

 of two or three years. ' Among the Melolonthini almost the converse obtains; the 

 larva takes two, three or even five years to mature, and the beetle, after emerging 

 from the ground, lives for only a week or two. 



In Ontario the most familiar of these phytophagous scarabs are the leaf- 

 chafers popularly known as June bugs. After three years passed in subterranean 

 obscurity the beetles emerge, often in vast quantities; they are inactive during the 

 day and remain hidden in the grass at the foot of trees or on the foliage itself, but 

 at dusk they rouse up from their lairs and fly about among the trees in irregular 

 flight, noisy and blundering: before midnight their activity on the wing ceases. 



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