870 



INSECTA. 



Forficul*, and Cicada (Jig. 353), the insect 

 is very much smaller, but has the general form 

 of the parent, without any rudiments of wings 

 or elytra. Another description of larva is that 

 in which the insect comes from the egg either 

 as a fat sluggish grub, or as an active and vora- 

 cious one, with an elongated body very 

 different in form from that of the parent, and is 

 furnished with but six legs, which are attached 

 to the anterior part of the body, in addition in 

 some instances to two processes employed as 

 legs at its posterior extremity. Examples of 

 the last of these occur in the voracious water- 

 beetles, Dyticidct, in the Carabides or ground- 

 beetles (Jig. 354) and many others ; and of the 



Fig. 354. 



Larva of Calosoma Sycophanta ( Burmeister). 



first, in the Chaffer-beetles Melolontha, and 

 stag and dung-beetles, Lucanida and Geotru- 

 pidce (Jig. 332). Other kinds of larvae, to 

 which the term is more strictly applicable, are 

 known to every one, as the caterpillars of 

 butterflies and moths. These and the pseudo- 

 caterpillars, the larvae of the saw-flies, Ten- 

 thredinida, (Jig. 355, A), are active and have 



Fig. 355. 



A, larva, and B, perfect state of Athalia centifoliae, 

 the saw-jiy of the turnip, (Newport, Prize Essay. ) 



elongated bodies furnished, in addition to the 

 six legs at the anterior part, with many others 

 along the posterior. They undergo a complete 

 metamorphosis, both of external and internal 

 conformation in passing from the larva to the 

 perfect condition. Besides these there are, as 

 in the instance of hornets (figs. 356 and 357) 

 and bees, larvae which are entirely destitute of 

 organs of locomotion, and exist simply as elon- 

 gated maggots; and others, as some of the 

 flesh-flies, Muscat, and the tailed maggots that 

 inhabit the most noisome puddles, Eristalis 

 tenax, which are entirely destitute of the true or 

 anterior legs, and have only those which are 

 attached to the abdomen. 



These kinds of larvae were formerly referred 

 by Fabricius, under special designations, to 



different kinds of metamorphoses, which those 

 designations were supposed to indicate ; but, as 

 remarked by Burmeister,* neither were the 

 terms employed in strict accordance with the 

 conditions of the larvae themselves, nor always 

 indicatory of the metamorphoses they were 

 about to undergo. We fully agree, therefore, 

 in the opinion expressed by Burmeister, that 

 the different kinds of larvae are referable to 

 only two kinds of metamorphoses ; the one a 

 metamorphosis incompleta, which consists sim- 

 ply in the insect shedding its skin and 

 increasing in size, and in some cases acquiring 

 new organs, but in all stages of its existence 

 continuing active, and having the form of the 

 parent, as in the instances above noticed; 

 and the other a metamorphosis completa, in- 

 cluding all insects which in the larva state have 

 a form different from the parent, and undergo 

 a complete change, both of external and inter- 

 nal conformation, before they arrive at the per- 

 fect state. 



But whatever be the form or changes of the 

 insect, the larva state may be looked upon as 

 its most voracious period of life. In many 

 species it is also its longest period. Those 

 which do not hybernate in the perfect state 

 exist but for a very short time as larvae ; while 

 those which continue for a long period in the 

 larva state, as the Lucanida and Melolonthidte, 

 some of which are said to continue for four 

 years, pass but a little while in the perfect. 

 But these periods are not always equally long 

 in different species of the same families. Thus 

 among the Apida, the Bombus terrestris, or 

 common humble-bee, exists but for a short 

 period in the larva, but a long one in the per- 

 fect state ; while in a closely allied genus An- 

 thophora retusa, one of the solitary bees, that 

 form separate nidi in vertical sections of dry 

 banks exposed to the sun, the insect often con- 

 tinues through the whole winter in the larva 

 state, and only exists for a few weeks of the 

 following summer in the perfect. On the 

 other hand the numerous species of Muscidte 

 exist but a short time as larvae, or maggots, but 

 a very long time as active flies. 



External anatomy of the larva. The body 

 of a larva is in general composed of thirteen 

 distinct segments, or divisions ; the first consti- 

 tutes the head, with the organs of manducation, 

 the second, third, and fourth, and, as we shall 

 hereafter see, in part also the fifth, together 

 form the thorax of the future Imago, while 

 the remaining ones form the third division of 

 the body, the abdomen. In most insects in the 

 larva state, the whole of these segments from 

 the second to the thirteenth are equally deve- 

 loped, and differ but little from each other in 

 their general appearance. The second, third, 

 and fourth segments have each a pair of short 

 scaly feet, the rudiments of the future limbs, 

 and the segments of the abdomen are often 

 furnished with soft membranaceous ones, which 

 disappear entirely when the larva undergoes 

 its metamorphosis. On each side of the body 

 there are in general nine oval apertures, the 



* Manual, Trans, p. 34. 



