Invertebrata. Zoological Collections. 371 



Hymenoptera, the characters of these parts in this family are very interesting 

 to the entomologist, as exhibiting the analogies of the mouth in two great 

 divisions of the class. 



The organization of the Hymenoptera is also remarkable in other respects. 

 In insects which grind the food, the body is divided into four principal parts : 

 the Head, Corslet, Thorax, and Abdomen. In the Hymenoptera, Diptera, and 

 Lepidoptera, the corslet is rudimentary, and almost disappears, the thorax 

 seeming to constitute the second part of the body. Entomologists have 

 therefore improperly called this part the corslet, — a name which belongs 

 to an entirely different part. This modification is best shewn in the Hy- 

 menoptera. 



The two pairs of wings, which appear for the first time in the Coleoptera, 

 the second order of insects, are differently developed in different orders. In 

 the Coleoptera, the second pair serves only for flight, and the first, or the 

 elytra, is composed of two solid scales, which protect the true wings, but do 

 not contribute to flight. In the Orthoptera the elytra already begin to be 

 veined and membranous, and, at the same time, take an active part in flight. 

 In the next order, the JSfeuroptera, and particularly in the Libellulce, the two 

 pairs scarcely differ from each other. Then, the elytra continuing to be 

 more and more developed, at length become more peculiarly the organs of 

 flight, whilst the second pair of wings gradually decreases in development ; 

 thus, in the Hymenoptera, the first pair is more than twice as large as the 

 second, and acts more efficiently in flying. This variation of size and 

 function, which the two pairs of wings undergo in inverse directions, is 

 also remarked in the two articulations of the thorax, which support them, 

 and are subordinate to them. 



A very remarkable fact in comparative anatomy is presented in the external 

 form of the brain. Several physiologists have thought, that, in the higher 

 animals, the degree of intelligence is in proportion to the number of 

 convolutions of the cerebrum : an opinion which seems to find additional 

 support in the Hymenoptera. These insects shew the highest intelligence 

 of all their class, and are the only ones whose brain, so called, presents well 

 marked convolutions. — Bull, des Sci. Nat. xxii. 347. 



Electricity of the Caterpillar of Cerura vinula Animal electricity, (that is, 



the voluntary power of communicating electricity,) is one of the strangest 

 phenomena in nature ; and this seems to accord so much with the general 

 sense of mankind, that any new fact of this kind is listened to with inatten- 

 tion, if not with incredulity. It has been allowed to be ascertained in some 

 fishes, and in one insect, a beetle from Brazil. What I am going to relate 

 establishes the existence of the power among caterpillars, at least to the 

 conviction of my own mind. 



Observing the leaves of a young poplar, of the species P. canescens, to 

 be much destroyed, I was led to examine the cause. Two large sorts of 

 caterpillars were feeding upon it, both to me, at that time, unknown ; and 

 the name of one of them I am still ignorant of: the other is now called 

 Cerura vinula. 1 broke off two twigs, with one of each, and was carrying 

 them home : the Cerura shewed decided symptoms of irritation, which 

 particularly drew my attention. It began to contract itself, drawing itself 

 closely together, and by degrees elevated and extended its bifurcated tail ; 

 and there were slowly protruded from each of the points bright red filaments, 

 about one-eighth of an inch long, and irregularly bent to one side. In a 

 short time I felt a sudden tingle along my arm, which made me stop with 

 surprise. Suspecting, however, that this might be imaginary, I again pro- 

 ceeded; and, shortly after, I felt another shock, which made me almost 

 involuntarily throw the twig with the creature upon the ground. As I waa 

 near the house, and one of the children with me, I sent her for a wine-glass, 

 in which I put the caterpillar, which immediately drew in its tails to their 



