290 ROBERT S. BREED AND ELSIE F. CALL. 



apterous forms, with elytra overlapping at the base. The same 

 author says that in some species the elytra are soldered together 

 along the suture. The degree of firmness of the joining varies 

 even in specimens of the same species, probably depending on 

 the age of the individual. 



I. Material and Methods. 



The material used was Lachuosterna fiisca Auct., the June-bug 

 or May-beetle, Tkymalus inarginicollis Chevr., a small beetle 

 which lives in the common shelf fungus of white birch, and 

 Tenebrio molitor Linn., the meal beetle. 



The method used in examining the co-adaptations of the elytra 

 in the two larger beetles was to take specimens hardened in 

 alcohol and cut off the posterior part of the body, wings and ely- 

 tra with a razor. Then the remainder of the insect was placed 

 under a low power of the microscope in such a position that the face 

 of the cross section could be viewed. In some cases it was found 

 advantageous to embed the whole beetle in paraffin first. Then 

 the desired section was cut free-hand with a razor, after which a 

 part or the whole of the paraffin was dissolved away and the cut 

 face examined with a microscope. When studying the separate 

 elytra, thin sections were cut in pith in the same way that botan- 

 ical sections are so often prepared. In this way perfect, though 

 rather thick, sections were obtained, whereas microtome sections 

 were badly broken. 



In the case of TJiyniahis, which is a small beetle with a com- 

 paratively thin cuticula, it was found possible to prepare series 

 of microtome sections of the entire insect. These series show 

 both the interlocking along the dorsal suture and the musculus 

 episternalis with its related parts. By selecting young imagines 

 of Lachuosterna and TenebHo and sectioning only a portion of 

 the body, series of microtome sections of these beetles were pre- 

 pared which show the musculus ej^isternalis and its related parts. 



2. Observations. 



There are commonly found in beetles four devices for fastening 

 the elytra in place, all of which may be utilized in one animal. 

 The fastening may be accomplished : 



I. By a co-adaptation of the elytra along the dorsal suture. 



