HARDWICKE'S SC lEN CE-GOSS IP. 



155 



limits of Victoria, and perhaps further, a flora 

 representing a wanner climate than at present 

 existing. Of such a nature are'.those fruits described 

 under the names of Rhytidotheca, allied to the satin- 

 wood tree ; CehjpJdna, probably allied to Helicia, a 

 genus of east and north Australia, and tropical 

 Asiatic trees, but not now living in Victoria, whilst 

 Conchotlma, perhaps one of the tropical Gervillece, 

 bears no resemblance to any member of the family at 

 present comprised in the flora of Victoria. Lastly, 

 we must not lose sight of the affinities borne by 

 some of these fossil fruits to those of the London 

 clay. li- il., JuK. 



THE MOUTH OF THE CRANE-ELY. 



THE following description of the mouth of the 

 Crane-fly must be taken by the readers of 

 Science-Gossip quantum valeat, as addressed by a 

 " Student and Lover of Nature " to " Students and 

 Lovers of Nature." It consists in great measure 

 of a comparison of the mouth of this insect with 

 that of the Blow-fly, as described iu Mr. Lowne's 

 " Anatomy of the Blow-fly,"* and in offering it for 

 publication I venture to hope that while it may 

 contain a sufficieut substratum of truth to render 

 it acceptable to the public, any inaccuracy of 

 statement into which I may have fallen will be 

 kindly corrected by those who may be qualified 

 for the task. I pass over any general description 

 of the mouths of insects, as this has been lately in 

 much better hands than mine, and for the sake of 

 those to whom the subject is new, will commence 

 with'a few remarks, chiefly explanatory of terms 

 which I shall have occasion to use, and without 

 which I cannot make my meaning i^clear, and shall 

 conclude with a short account of the modus operandi 

 employed in my dissections, with a view to encourage 

 those who might wish to follow them out, but who 

 may possibly be deterred by over-estimatmg the 

 difficulty of so doing. 



When two different creatures are compared, and 

 certam parts in the one are found to correspond 

 with, and to take the place of, similar parts in the 

 other, thcD, however different may be the office they 

 fulfil, the parts are said to be homologous, and the 

 one part is said to be the homologue of the other^ 

 Thus, the arm of a man and the wing of a bird are 

 said to be homologous parts, and also iu the insect 

 before us, the balancers which take the place of the 

 second pair of wings iu such as have two pairs, are 

 said to be the homologues of that second pair. 



The use of the term "plate," as applied to 

 designate a portion of the integument of insects, 



* Such references to this work as require an acquaintance 

 therewith I shall insert in the form of notes, which may be 

 disregarded by the general reader. 



should be well understood. It is not intended to 

 indicate any separation of parts. It is important to 

 bear in mind that the iutegument of insects forms 

 a continuous covering in which no break can be 

 found, over every part of the creature. Certain 

 parts are, however, strengthened by the deposit of 

 a horny substance, called cMtine, and these are 

 more or less distinguishable as plates, from the 

 intermediate soft and transparent portions which 

 connect them with one another. An examination 

 of the abdominal plates of a fly or a beetle will 

 best illustrate this. 



Each of the parts of the mouth of an insect 

 being a hollovf organ has an external surface or 

 plate, and an internal ditto. Those belonging to 

 the labium have been recognized respectively as the 

 mentum and the posterior labial plate, or floor of 

 the mouth, mentioned by Mr. Lowne.* I have not 

 seen any similar distinction in the case of the labrum, 

 but shall introduce it for the purpose of my descrip- 

 tion, calling a the external plate of the labrum, and 

 b the internal plate of the same, the latter being 

 also the part referred to as the roof of the mouth, 

 as opposed to U, its floor. 



With reference to the salivary duct, of which 

 mention will hereafter be found, I should say that 

 the saliva of insects is an acrid juice, secreted by 

 special glands situated in the thorax, and emptying 

 their contents by appropriate ducts either into the 

 cavity of the mouth, or into the commencement of 

 the stomach. Its penetration into the wound is the 

 cause of the irritation produced by the bite of 

 various insect-pests, with which we are all familiar. 

 It only remains for me to add that if the head of 

 the insect be cut off and. placed with the antenna 

 uppermost, that surface of the head which bears 

 the antennse will be the superior surface ; the use 

 of the terms inferior, anterior, posterior, and lateral 

 will not need further remark. 



The head of the Crane-fly consists of a somewhat 

 globular chamber bearing the great compound eyes 

 and the antennse, from the fore part of which arises 

 a cylmdrical prolongation which I recognize as the 

 rostrum described by Burmeister,t and stated by him 

 not to form a distinct organ, but to be merely a con- 

 tinuation of the corneous covering of the head-^The 

 parts of the mouth or trophi, as they are sometimes 

 called, which form the subject for our present con- 

 sideration, are situated at the extremity of this ros- 

 trum ; some of them are, however, prolonged inter- 

 nally some distance into the head. They are as 

 follows, viz : — 



I. — The labrum, consisting of — 



1. An external plate. 



2. An internal do., forming the roof of the 



mouth. 



* Lowne's " Anatomy of the Blow-fly," p. 47. 

 t Page 51, Shuckard's Translation, 1836. 



