108 



HARDWICKE'S SCIENCE -GOSSIP. 



latter its solidification is brought about with great 

 rapidity, by a most elaborate spiuoing apparatus. 

 Although the mouth of the larva of the Goat- 

 moth (Cossus liguiperda) serves well enough as au 

 example of the gnawing and silk-spinning mouths 

 of the lepidopterous larvae, which are all very 

 similar, that of the adult Goat-moth will by no 

 means serve as an example of the mouth of the 

 adult lepidoptera, for, from the entrance of the 

 larva into its !pupa state, the moutli retrogrades 

 in its development, and undergoes atrophy or wast- 

 ing in this insect, so that the adult moth is without 

 the means of feeding. 



Fie:. '6. The mouth of a Lepidopterous larva seen frnm below, 

 o, antennse ; oc, ocelli; lb, labmm ; m^', wix", md, niaxillfe 

 and mandiblts. 



In most lepidoptera, however, a very perfect 

 suctorial mouth is developed, so different from that 

 of the larva, or indeed from that of any other class of 

 insects, that its parts are only recognized with dif- 

 ficulty and uncertainty, except when their develop- 

 ment is most carefully watched ; and all their rela- 

 tions with each other are exa.ntiined with great 

 patience. 



Fig. 77. Longitudinal section of the mouth of a lepidopterous 

 larva, seen from the middle line, m, cavity of the mouth ; 

 Ir, labrum. 



The most conspicuous and remarkable organs in 

 the lepidopterous mouth are two spirally curved multi- 

 segmented half-tubes (fig. 7S, s). These are called 

 the antlia or pumps ; they lie side by side, and form 

 together a complete tube ; they are exceedingly mov- 

 able, all their joints being endowed with muscles like 

 those of ihe tongue of a bee. Tlie antlia are not 

 covered by hairs like thebce's tongue, but have scales 

 atintervals, especially towards the terminal extremity, 



where these frequently form a kind of brush. The 

 sides of the mouth are furnished with a pair of 

 great jointed organs called palpi (fig. 78, jo), covered 

 with a profusion of beautiful scales. At the base 

 of these organs a pair of small curved plates lie, one 

 on either side of the antlia. The labrum is rudi- 

 mentary, and the labium is apparently wanting, 

 or represented only by the anterior edge of the floor 

 of the mouth. 



The interpretation of the nature of these organs 

 is a matter of no little difficult}', and the reason of 

 this is, as has been already stated, that the changes 

 in the pupa stage of the life of a lepidopterous 

 insect are exceedingly remarkable. Certain pouches 

 built of very delicate cells, exist in the head of the 

 larva : these were first fully described by Landois, 

 in Germany, and are now well known in this country 

 as Imaginal discs. The origin of these structures is 

 most difficult to trace ; but they are derived, I think 

 there can be little doubt, from the inner layer of 

 the cellular integument of the nipple-like projec- 

 tions, which, as we have already seen, are the first 

 rudiments of the mouth-organs of insests. 



Fig. 78. Side view of the head of a moth, showing the com- 

 pound eyes, o ; the antennae, a ,• the palpi, p ; the antlia, ». 



The little pouches or discs, originating in this 

 manner, remain, however, soft cellular structures, 

 and grow but little during the earlier stages of 

 larval life. As the larva grows, they become detached 

 from the organ from which they were originally 

 derived, but retain their connection with certain 

 nerves and tracheal vessels. When the larva ceases 

 to feed, they undergo rapid development, and 

 gradually unfolding, spread out, and form a new 

 integument within the larva. This becomes the 

 pupa-case, with its several pouches moulded into 

 the forms of the wings, legs, and the mouth-organs 

 of the perfect insect. There is no more delicate or 

 difficult task than to trace all the changes of the 

 imaginal discs from their earliest appearance in the 



