The First of the Five Native Grape-feeding Sphinx: Diadema inscriptum

We found a larva and three eggs of the lettered sphinx (Diadema inscriptum) on grape vines (Vitis sp.) and Virginia creeper (Parthenocissus quinquefolia), the first find of this year for the species. 

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If you've skimmed through some of our last summer's posts, then you would have seen that there are five native sphinx species here in Ithaca that specialize on Vitaceae (grapes [Vitis] and Virginia creeper [Parthenocissus quinquefolia]). Namely, these species are the lettered sphinx (Diadema inscriptum),  Nessus sphinx (Amphion floridensis), Abbott's sphinx (Sphecodina abbottii), Virginia creeper sphinx (Darapsa myron). and Pandora sphinx (Eumorpha pandorus). 

Since grapes and Virginia creeper vines are extremely common here and are relatively easier to search through due to their small size, hunting for these grape-feeding sphinx became one of our prime activities during collecting trips. The seasonal flights of the five species all differ somewhat, meaning we were always occupied with at least one or two of them throughout the whole season last year.

To summarize (based on our personal observation): lettered, Nessus, and Abbott's appear to have a single early season flight starting in May (as soon as the vines first grow in) and continuing into June, with lettered being the most commonly encountered during this time; myron has continuous flights (highly multivoltine) throughout the entire season from June to September (?), and is by far the most commonly encountered (sometimes only) species throughout most of the season; Pandora has a single (?) late summer flight starting in late July until September (?) and is much less frequently encountered relative to myron. 

Since the vines are just now beginning to grow leaves, we have been occasionally skimming through them in anticipation of one of the early season sphinx. The past week we haven't had much luck (seemed to be a tad early), but today by complete chance, we came across a first instar lettered sphinx larva on the grape vines behind the Law School (West Campus).  A quick look through the other vines in the area yielded three shiny green eggs, one slightly developed and the others fresh, all on virginia creeper. ​

The larva was resting on the vine of a new shoot and feeding on the buds and the three eggs were found on the upper and under side of young leaves. We observed last year that the moths seem to have a ovipositing preference for new shoots and buds which still appears to be true. We could tell that the larvae and eggs were the lettered sphinx (and not Nessus or Abbott's) simply based on the small size and bright, yellow-green coloration. Both Nessus and Abbott's are larger with slightly different shades of green; Nessus tends to be a duller (not yellowish) green,  and Abbott's is pale and whitish. 

Now that we've found a larva and a few eggs, we know the flight of this (and probably other) grape-feeding sphinx species has begun, despite how early in the season it is. We look forward to finding more in the coming weeks!

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Alan Liang​
​Alan Liang is a student at Cornell University in Ithaca, New York pursuing an undergraduate degree in entomology. He is co-owner and a main contributor of the Liang Insects blog and photographs.

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