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as are the tarsi entirely ; the tibiae are yellow. The thorax is black with a white median 

 stripe, and the wing-cases are prettily mottled with brownish dots which form a dark 

 triangular spot, in the middle of each, with the base on the costal margin ; there is also a 

 dark spot at the junction of each nerve with the margin, which has the effect of leaving a 

 more or less distinct sub- terminal white band. The colours vary considerably, but seem 

 to be darker in the females. The abdomen of the male is terminated by several bristle- 

 like appendages, and that of the female by a conical ovipositor. In general appearance, 

 although little more than one line in length, these insects much resemble miniature Cicadae. 

 I found that many of the galls of this species also were polythalamous, one which I opened 

 containing four pupae. The occurrence of this insect at Ottawa is somewhat interesting. 

 The three trees of Celtis occidentalis upon which the galls occur are the only specimens 

 of that tree which I have found in this locality, during four years of constant botanical 

 investigation. Prof. Macoun, too, tells me that with the exception of a small grove at 

 Belleville these are the only specimens he has heard of east of Toronto. It is evident 

 then that it is quite uncommon, and yet these trees were so thickly covered with galls 

 that the leaves in many instances had more than a dozen galls on their undersides, and 

 had much more the appearance of bunches of berries than of foliage. How did these 

 small insects which only feed on this tree traverse so great a distance from one locality 

 to another 1 The gall is mammiform, having a thick fleshy outer coat, and inside this a 

 thin woody one ; the cavity inhabited by the flat larva is narrow, and the centre of the 

 gall is filled up with a solid mass of the same nature as the outside wall. When the pupae 

 are mature they work their way up through the top of the galls, which are all on the 

 underside of the leaves, and come out on the upper surface. 



The other genus in this division is Aphis. These exceedingly injurious iusects which 

 attack almost every form of vegetation, are too well known to need any elaborate descrip- 

 tion. The word Aphis is derived from a Greek word meaning to exhaust. Although 

 most of these insects are of small size, very few exceeding one or two lines in length, yet 

 they make up for their want of size by their vast numbers ; the rapidity with which they 

 increase, is almost beyond credence. " Reaumur has proved that one individual in five 

 generations may become the progenitor of nearly six thousand millions of descendants." 

 (Harris, p. 235). 



In the autumn the perfect Aphides pair, and the female lays an egg on the branch of 

 a tree which hatches the next spring. The newly-born larva immediately begins its work 

 of depredation, piercing the young leaves and shoots with its sharp beak. It grows 

 rapidly and soon arrives at maturity. The Rev. J. G. Wood, in " Insects at Home," gives 

 the following concise history of their lives : — " These insects are prolific almost beyond 

 belief. As a general rule, insects lay eggs which are hatched, pass through the state of 

 larva and pupa, and then become perfect insects. But the Plant-lice go on a very different 

 plan. Sometimes as if to show that thej are amenable to law, they do lay eggs ; but this 

 is the exception and not the rule, which is somewhat as follows, though varied every now 

 and then by these most eccentric of insects : A female Aphis takes her place on a branch 

 — say of the rose — plunges her beak into the tender bark and begins to suck the sap. 

 After a short time she begins to produce young Aphides at an average of fourteen per 

 diem. These young creatures are just like their mother, only less, and immediately follow 

 her example by first sucking the sap of the plant and then producing fresh young. As to 

 the opposite sex it is no business of theirs. The extent to which this peculiar mode of 

 increase (gemmation) can be carried may be imagined from the fact that a single female 

 Aphis, isolated from the other sex, began to produce prolific females, which, in their turn, 

 produced others, and so on for four years, during the whole of which time not a male 

 Aphis had been suffered even to approach them. It is in consequence of this remarkable 

 mode of production that the twigs and buds become so rapidly covered with Aphides, the 

 quickly succeeding generations crawling over the backs of their predecessors so as to arrive 

 at an unoccupied spot of bark in which they can drive their beaks. Thus, at the beginning 

 of a week, say on Monday, a rose-tree may be apparently free from Aphides, or have at 

 the most six or seven of the 1 blight ' upon it, but by Thursday the whole plant will be so 

 thickly covered with Aphides that scarcely a particle of the bark can be seen." 



