90 Mr. A. S. Packard on the Development 



pause in the metamorphosis for a special biological design, such 

 as obtains in the Lepidoptera and the majority of lower Insects, 

 The terms larva, pupa, and imago are therefore not absolute 

 terms. 



Suhimago State. 



Certain individuals which would upon a casual glance be mis- 

 taken for " pupae " differed so much from what we have called 

 pupae above, that they may be said to be analogous to the sub- 

 imago state of Ephemeridae. In this state the arthroderm, 

 owing to the rapid deposition of chitine, is denser and harder ; 

 the wings are as large as in the perfect bee, and the joints of 

 the legs are spiny, while the ovipositor has become wholly 

 withdrawn within the walls of the abdomen. 



In some specimens, remains of a thin pellicle were found upon 

 the extremities; so that we are neither justified in calling this 

 individual an imago nor, on the other hand, a pupa. The indivi- 

 duals had not left their cells. Their feet had not yet been used 

 for purposes of locomotion, nor their jaws to assist in making 

 their way out of their cells, while the hairs are nearly concolo- 

 rous all over the body, though very faintly shaded with yellowish 

 on the dorsal and lateral portion; so that the species can be 

 distinguished, as some of the specific characters depending on 

 ornamentation are at this time apparent. We have observed 

 facts indicating three moultings of the skin during the so-called 

 pupa state, in distinction from the larval and imago states ; and it 

 is highly probable that there are more. During the larval con- 

 dition it would be safe to say that there are four distinct moult- 

 ings, as there are five distinct sizes of larvae. In some of the 

 eggs the larval forms can be indistinctly seen through the thin 

 walls, which we would homologize with the skin of the insect 

 after birth ; for the fertilized egg must be regarded as the 

 insect in its inception, in a state equivalent to the larval, pupal, 

 or perfect state of the insect. The genus Bombus, therefore, 

 may be considered to undergo a series of at least ten moultings 

 of the skin ; and we are inclined to think further observations 

 will tend to increase the number. Lubbock* has described 

 twenty in Ephemera ; and five have been noticed in several 

 genera, such as Meloe and others. 



, The sexes of the larvae can be easily distinguished, as the 

 genital armature appears through the transparent skin. 



The specific differences between the larvae of the different 

 species of Bombus are of the slightest possible amount, as they 

 only differ in size, the rings of the body being smooth or rough, 



♦ Trans. Linn. Soc. yol. xxiv. part 2 (1863), 



