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OONTKNTS OF No. 169, 



PAGB 



The EntomolofTT of ft Pond, illlus.) 



By E. A. Butler 61 



Our Two Brains. Bj Sicbard A. 



Proctor 62 



The Young Etectridan. Bv W. 



Slinzo .'. 63 



First Star Lessons. {Jf'ith Map.) 



Bj Richard A. Proctor 61 



Thought and Langusge. II. By Ada 



S. Ballin 64 



-Manners and Customs in America. 



Br Richard A. Proctor 66 



3)ino9aur9. (lUut.) 67 



Refomialion in Tiiur*- Koeping. 

 (///»..) By W. F. Allen 



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THE ENTOMOLOGY OF A POND. 



By E. a. Butler. 



ABOVE THE SURFACE {continued). 



1'^HREE different families of flies contribute to the 

 dancing swarms mentioned in our last paper, the 

 €idicid(e, or gnats proper, the C/iironomidn', or midgfs, 

 and the TipuUdce, which includes the winter gnats and 

 daddy-longlegs. But those of the last family are not 

 aquitic in early life ; the genus Trichocera, which belongs 

 to this family, furnishes the so-called gnats that sally forth 

 in swarms during bright sunshine in the winter month?. 

 The swarming of these is dependent upon the w-eather, for 

 it has been observed by the Rev. A. E. Eaton that their 

 style of flight varies with the temperature. A cold below 

 3G° Fahr. puts a stop to their f.iiri il excursions altogether, 

 and drives them to their places of retreat under boards, 

 ic. ; at temperatures a little above this they will venture 

 forth singly, but when -15" Fahr. is reached they are then 

 able to congregate in multitudes and dance for joy. But, 

 though thus forming swarms, and so resembling the gnats 

 proper, they diSer from them, as above-mentioned, in not 

 being aquatic. We must not suppose, therefore, that all 

 gnat-like creatures — nor, indeed, all that fly in swarms — 

 have spent the early part of their Ufa in the water, and it is 

 only with such as have done so that we are now concerned 

 — viz., the Culicidce, or gnats, and the Chironomid(i\ or 

 midges. 



A great amount of human suflering often follows from 

 causes apparently the most insignificant, and no better 

 illustration of this can be found than is afforded by the 

 insects we have first to consider — the Culicidfi', or gnats 

 and mosquitoes, the latter being included because, though 

 not truly British insects, they are closely allied to our own 

 familiar gnats. If, in the absence of personal knowledge, 

 one were to endeavour to conjecture the probable form of 

 on:; of these little pests, from the agonising tales of the 

 persecutions to which humanity is subjected by them, the 

 imagination would naturally conjure up a formidable 

 figure, with " danger " emVjlazoned, as it were, in its very 

 aspect ; but the reality is vastly ditTerent from any such 

 conjecture, and it is almost impossible to believe that .so 

 frail, so insignificant a creature as these really are can 



inflict such torments. The CuHo'da; as a family, are indeed 

 answerable for a vast amount of h\inian .snllcring; and 

 while it is true that our share of it in this country is com- 

 paratively trifling, yet even hero they not unfrcqurntly 

 cause considerable annoyance. They form one of the most 

 widely distributed families of insects; not only do they 

 swarm in the tropics and tem])eratc regions, but even the 

 cold of Arctic snows is not .siillicient to check their nuilti- 

 plicatiou and exterminate their race. 



Let us now endeavour to draw the portrait of a gnat, 

 and be it remembered that what is here said of a gnat is 

 applicable in almost every respect to the mosquito as well. 



First, a gnat is a Dipterous insect, that is, it is possessed 

 of only a single pair of wings, that corresponding to the 

 front pair in other insects ; but though there arc no hind 

 wings fis such, the missing organs arc not wholly unrepre- 

 Ecnted, but their place is taken by a pair of exquisitely 

 delicate knobbed stalk.s, lik(! tiny clubs, which have been 

 called, inditlVrently, " haltcres," "balancers," "poisers," 

 from a notion that they aided the insect in maintaining its 

 equilibrium in its aviial journeys. In all the long-legged, 

 slender bodied divi.sion of the flies, these peculiar organs are 

 particularly conspicuous, and no better example could be 

 obtained for studying their peculiarities than an ordinary 

 daddy-longlegs (Fig. 1), one of the largest representatives 



Fig. 1. — Forewiiig and " Balancer'' of D.iilily-I.onglcgs. 



of the section. It is very diflicult to say what is their exact 

 function, if, indeed, they have not more than one. I^ome 

 have supposed them to be organs of hearing, others, of 

 respiration ; but after all that has been said on the subject, 

 their exact use still remains problematical. The upper pair 

 of wings are long, narrow, membranous, and clear, though 

 in some species pi'ettily spotted. Attached to the nervures 

 are some tiny scales similar to those on a butterfly's wing, 

 and ethers of kindred nature fcrm a clothing for the body. 

 F^ach scale is really composed of an extremely delicate 

 double membrane, strengthened on each side with longi- 

 tudinal ridges, those of the oppo.site sides uniting at the 

 broad end of the scale, where they form a series of points 

 projecting beyond the membrane itself. The legs aie long, 

 and extremely slender, and easily part company with the 

 body. The head of the male carries a pair of exquisite 

 antenn;e, in the form of plumes, somewhat as one might 

 imagine Liliputian ostrich feathers to be ; those of his 

 spouse are much simpler organs, with very short lateral 

 appendages. 



Ttie terrible weapon that renders these insects so annoy- 

 ing, consists of the organs of the mouth ; but before we 

 can under:-tand them properly, it will be necessary to refer 

 to the general plan of an insect's eating apparatus, for 

 notwithstanding the many and mighty differences in 

 this part of its organisation, shown in the various orders 

 of insects, they are all modifications of one type of struc- 

 ture. Imagine, then, an aperture bounded above by a 

 transversely placed organ, the lahrum, or upper lip, and 

 below by a pair of organs, usually more or less coalesced 

 into a single one, the Inhhnu, or lower lip. Between these 

 two, and bounding the sides of the aperture place first, and 

 nearest the labrum, a pair of organs so aiticulated as to 

 be capable of lateral motion only, the iiKiiidihhtt, and 



