Mallow Leaf Mining Beetle
Stenopodius flavidus
The host plant is Desert Globe Mallow, Sphaeralcea ambigua, a member of the Malvaceae. 11 July, 2015, at Phoenix, Maricopa Co., Arizona.
Chrysomelidae -- Leaf Beetle Family
What most people refer to as a 'small' insect or beetle is most likely a rather large one compared to the sizes of most species. These leaf miners are about 4 mm in length and rather flattened. The compressed shape is an adaptation for living in the narrow space between the upper and lower surface of a leaf blade. Pale spots appear where the larvae (grubs) have tunneled through. The tunnels and adult beetles are so small that close inspection of the plant is needed to see them at all.
The three pale spots in this Sphaeralcea leaf are where the larvae have eaten away the leaf tissue from the inside what was a rather thick leaf. 28 July, 2015, at Phoenix, Maricopa Co., Arizona.
This pupa was disected from one of the leaf mines above. It is a resting stage during which time metamorphosis changes the grub into an adult beetle. A dark eye can be seen at right. Length of pupa is about 3 mm. This close-up also shows well the stellate (star-shaped) hairs that are characteristic of globe mallow plants. 28 July, 2015, at Phoenix, Maricopa Co., Arizona.