156 



THE AMERICAN ENTOMOLOGIST. 



this genus (Decatoma), bred from the above 

 galls and now in the collection of the Senior 

 Editor, is 217. Those that require further in- 

 formation on this somewhat dry subject are 

 referred to the forthcoming Scientific Article by 

 the Senior Editor, in which will be found de- 

 scriptions of about a dozen new species belong- 

 ing to these two parasitic genera {Eurytoma 

 and Decatoma). 



We will now give lateral or profile views of 



the same Joint-worm Fly, the female of which 



has been drawn as viewed from above in Figure 



113, b. Compare these profile views with those 



[Fig. ai7.] 



Color— Black, 

 of the two true parasitic genera {Eurytoma and 

 Decatoma) given in figures 115 and 116, and it 

 will be seen at once, even by the unscientific rea- 

 der, that the last insect is totally unlike either of 

 the two first, and manifestly can not be referred 

 to the same genus. Not to dwell upon structu- 

 ral minutife which willbe explained elsewhere, it 

 will be seen at once that in the Joint-worm Fly 

 (Fig. 117, a § , 6(3') the abdomen in both sexes, 

 but especially in the female, is shaped quite dif- 

 ferently from that of either of the two parasitic 

 genera (Figs. 115 and 116), and that the body 

 is nearly straight in repose, instead of being 

 curled into a semicircle as in the two first 

 genera. This latter peculiarity is not a mere 

 fortuitous circumstance, happening to particu- 

 lar individuals, but is universal in all specimens 

 belonging to the two genera first figured {Eury- 

 toma and Decatoma) ; so that it is with great 

 difliculty that their bodies can be sufficiently 

 straightened out in death, to admit of their 

 being mounted upon card in the comparatively 

 straight posture shown in the figures (115 and 

 IIC), their heads being usually found stifliy 

 doubled up downwards upon their tails. Even 

 in life, they frequently assume this posture, 

 when they wish to "play opossum" and escape 



the attention of the observer. On the other 

 hand, the Joint-worm Fly has no such peculi- 

 arity either in life or in death, or at all events 

 but to a very limited extent. 



A very curious chapter might be written on 

 the difierent modes in which different insects — 

 upon the same principle as that just now ex- 

 plained — form themselves into the similitude of 

 a round ball-like seed or pellet of dung, and 

 thereby escape the attention of their enemies. 

 To refer to but a few of such cases : Among 

 the Beetles, one genus {Byrrhus) has separate 

 cavities on the lower surface of its plump oval 

 body to receive each leg, the leg doubling up 

 and fitting into the cavity as smoothly, as does 

 each particle of the finest piece of mosaic work 

 into its appropriate position. In other genera 

 {Agathidium, Leiodes, Clambus and Sphwro- 

 morphus)the body itself is rolled up downwards, 

 head and tail together, into a more or less com- 

 plete and smooth ball. In the well known Cur- 

 culio (Conotrachelus nenuphar, Herbst) and 

 many other Snout-beetles, the beak in repose 

 is laid along the breast between the front legs, 

 certain genera having a deep groove there to 

 receive it; and the legs being then crumpled 

 up close to the body, the whole creature looks 

 exactly like the dead bud of a tree. In other gen- 

 era of beetles {Clilamys and Exema), belonging 

 to the same great Family (Chrysomela) as the 

 Colorado Potato Bug, the whole upper surface 

 of the body is rough, dai-k-colored aud opaque ; 

 and when the legs are retracted, even good ento- 

 mologists have been often deceived into mistak- 

 ing the insect for a pellet of dung voided by 

 some large caterpillar. Lastly, among the 

 Golden-tail Flies {Chrysis family) in the Order 

 Hymenoptera, all the genera, when threatened 

 with danger, roll themselves up head and tail 

 together, leaving their wings exposed. In this 

 case, as indeed in all other such cases hitherto 

 recorded in any Order of Insects, the little 

 creature curls itself up downwards, and the back 

 forms the convex aud the breast the concave 

 side of the ball into which it contracts itself. 

 The same thing holds good with certain genera 

 of Sow-bugs {Oniscus family) belonging to the 

 Crustaceans, which roll themselves up into a 

 more or less complete ball. But there is a re- 

 markable and hitherto undescribed genus of 

 Chalets flies, a single species of which (^Anti- 

 gaster mirabilis, n. sp.) exists in the Cabinet 

 of the Senior Editor, and which will be found 

 figured below, 1st iu Figure 118, fl, as viewed 

 from above with the wings and legs expanded, 

 2nd in Figure 118, b, in profile when preparing 

 to curl up, and 3rd in Figure 118, c, in profile, 



