24 UNITED STATES NATIONAL MUSEUM BULLETIN 276 



Egg masses are of two basically different types: the "helical" 

 egg mass, which is laid completely encircling small twigs; and the 

 "clasping" egg mass, which is laid on small twigs or larger branches, 

 or even on small trunks an inch or so in diameter, but is not laid as an 

 encircling mass although, if the egg mass is laid on a very small twig, 

 the last few eggs may overlap the first ones. 



Helical egg masses are laid by M. disstria (figs. 108, 113), M. con- 

 strictum (fig. 107), and M. tigris (fig. 106). In laying this type of egg 

 mass, the female positions herself at right angles to the twig and lays 

 her eggs in a continuous band four to six eggs wide as she crawls around 

 the twig (fig. 108). She usually circles the twig three or four times 

 and aligns the eggs in a continuous helix so that it is difficult to dis- 

 tinguish one turn around the twig from the adjacent ones (fig. 106). 

 Often the eggs are so perfectly laid that they appear to be in diagonal 

 rows inclined about 45° to the axis of the twig. As she nears the end 

 of the egg mass, she reduces the width of the band of eggs she is laying 

 until the last eggs are laid by twos or singly, resulting in a fairly even 

 edge which is carefully covered with spumaline (if the species is one 

 that normally covers the eggs with spumaline). The female is quite 

 persistent in trying to cover the eggs completely, and, on one occasion, 

 a female M. disstria was observed to try for 45 ininutes to cover the 

 exposed edges of the last five eggs she had laid, although she had 

 evidently exhausted her supply of spumaline. 



Clasping egg masses are laid by M. americanum (figs. 109, 110, 111), 

 M. calif ornicum (figs. 105, 112, 115, 116), and M. incurvum (figs. 114, 

 117). In laying this kind of egg mass the female again positions herself 

 at right angles to the axis of the twig or branch, but instead of laying 

 a continuous helical band of four to six eggs, she lays them in individual, 

 slightly curved rows by extending the tip of her abdomen to one side 

 as far as she can reach, and then laying a row of 10 to 15 eggs until 

 she cannot reach any farther to the opposite side. Before laying the 

 next row of eggs she may move forward slightly. She repeats this 

 procedure until nearly all of her eggs have been laid. As she nears 

 the end of the normal egg mass she shortens the rows and finishes by 

 covering all exposed edges with spumaline. This method of laying 

 results in slightly curved rows of eggs. Occasionally, half-moon shaped 

 c^'g masses are found with the concave edge of the &gg mass not covered 

 with spumaline. These result from the female being disturbed while 

 laying. 



It is evident that the final shape of the clasping type of egg mass 

 depends on the diameter of the twig or branch on which it is laid. 

 If the eggs are laid on a large branch or near the base of a small trunk, 

 the egg mass will be nearly flat since the eggs can be laid on only one 



