ig2 



THE YOUNG NATURALIST. 



of a small room. Could we but artificially increase this motion to the 

 speed attained by the living insect, the chirrup would be produced 

 with all its actual power and volume. The silence of the female 

 Acheta is owing to the absence of the stridulatory apparatus such as is 

 found to characterise the male. 



The increasing length of this paper warns me that I shall again 

 have occasion to dwell upon the subject of sound production at some 

 length, and it will be necessary to leave many orders with little more 

 than bare mention. Such omission must include the interesting group 

 of insects included in the Heteroptera, such familiar friends as the 

 Water Boatmen (Notonectida), Water Scorpions (Nepida), and Bed 

 Bugs (Cimicidce) being left for a future communication. I will merely 

 remark, en passant, that the latter insects have only rudimentary 

 wings, though winged individuals are stated to have occurred ; but 

 the fact, if fact it be, needs confirmation. 



The Aphaniptera, though constituting a too familiar group, are very 

 imperfectly known, as far as regards the functions of certain parts of 

 their structure. They evidently possess a pair of exceedingly rudi- 

 mental wings, thus defined by Mr. Westwood : " The mesothorax has 

 a small scale affixed at its hind margin, on each side, behind the coxa 

 of the middle legs, and resting upon the coxa of the hind legs, whilst 

 the metathorax has a much larger pair of these scales, which 

 nearly cover the sides of the first and part of the second abdominal 

 segment." I have not been able to make a necessary and careful 

 comparison between fleas of different species, but as regards PnUx 

 irritans, the description seems to me to be somewhat incomplete. 

 The second pair appear to be of a higher development than a mere 

 scale, but in the absence of comparative material, I am unwillingly 

 compelled to pass over this order without further comment. 



The anterior wings of Coleoptera are quite useless for flight, the 

 two primordial membranes having become greatly thickened and of a 

 horny texture. They are, as with the generality of true wings, united 

 around their edges and also at numerous points on their inner surface, 

 by horny columns, clearly a survival of the system of hexagonal 

 areolation and consequent adherence of the membranes as before 

 referred to. The hinder pair of wings are, as a general rule, exceed- 

 ingly well developed, and, not only folded longitudinally, but in those 

 species in which the length of the wing is considerably greater than 

 that of the protective elytra, are likewise doubled over. The wing- 

 cases, or elytra, as they are termed, vary very much in their 

 amplitude, being in some instances very short, as in the Staphylinidcz ; 



