130 BRISTLE- TAILS AND SPRING-TAILS. 



of straggling spinules. In all these particulars, the mandible of 

 Lepisma is comparable with that of certain Coleoptera and Neu- 

 roptera. So also are the maxillae and labium, though we are 

 not aware that any one has indicated how close the homology 

 is. The accompanying figure (152) of the maxilla of a beetle 

 may serve as an example of the maxilla of the Coleoptera, 

 Orthoptera and Neuroptera. In these insects it consists almost 

 invariably of three lobes, the outer being the palpus, the middle 

 lobe the galea; and the innermost the lacinia; the latter under- 

 going the greatest modifications, forming a comb composed of 

 spines and hairs varying greatly in relative size and length. 

 How much the palpi vary iu these groups of insects is well 

 knowu. The galea sometimes forms a palpus-like appendage. 

 Now these three lobes may be easily distinguished 

 in the maxilla of Lepisma. The palpus instead of 

 being directed forward, as in the insects mentioned 

 above (iu the pupa of Ephemera the maxilla is 

 much like that. of Lepisma), is inserted nearer the 

 base than usual and thrown oft' at right angles to 



,-, „.- ■„ the maxilla, so that it is stretched out like a leg, 

 152. Maxilla. ' "' 



and iu moving about the insect uses its maxillae 



partly as supports for its head. Thej' are very long and large, 



and five or six-jointed. The galea, or middle division, forms a 



simple lobe, while the lacinia has two large chitinous teeth on 



the inner edge, and internally four or five hairs arising' from 



a thin edge. 



The labium is much as in that of Pcrla, being broad and short, 

 with a distinct median suture, indicating its former separation 

 in embryonic life into a pair of appendages. The labial palpi 

 are three-jointed, the joints being broad, ancj in life directed 

 backwards instead of forwards as in the higher insects. 



There are five American species of the genus Lepisma in the 

 Museum of the Peabody Academy. Besides the common L. sac- 

 charina? there are four undescribed species; one found about 

 outhouses and cellars, and the heat-loving form, perhaps an 

 imported species, found in a kitchen in Salem, and apparently 

 allied to the L. thermophila Lucas, of houses in Brest, France; 

 and lastly two allied forms, one from Key West, and another 

 from Polvon, "Western Nicaragua, collected by Mr. McNiel. 

 The last three species are beautifully ornamented with finely 

 spinulated hairs arranged iu tufts on the head; while the sides 



